The targeting of gastrin-releasing peptide receptors (GRPR) was recently proposed for targeted therapy, e.g., radiotherapy. Multiple and frequent injections of peptide-based therapeutic agents would be required due to rapid blood clearance. By conjugation of the GRPR antagonist RM26 (D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2) to an ABD (albumin-binding domain), we aimed to extend the blood circulation of peptides. The synthesized conjugate DOTA-ABD-RM26 was labelled with indium-111 and evaluated in vitro and in vivo. The labelled conjugate was stable in PBS and retained specificity and its antagonistic function against GRPR. The half-maximal inhibitory concentration (IC50) of In-nat-DOTA-ABD-RM26 in the presence of human serum albumin was 49 +/- 5 nM. [In-111]In-DOTA-ABD-RM26 had a significantly longer residence time in blood and in tumors (without a significant decrease of up to 144 h pi) than the parental RM26 peptide. We conclude that the ABD-RM26 conjugate can be used for GRPR-targeted therapy and delivery of cytotoxic drugs. However, the undesirable elevated activity uptake in kidneys abolishes its use for radionuclide therapy. This proof-of-principle study justified further optimization of the molecular design of the ABD-RM26 conjugate.

The targeting of gastrin-releasing peptide receptors (GRPR) was recently proposed for targeted therapy, e.g., radiotherapy. Multiple and frequent injections of peptide-based therapeutic agents would be required due to rapid blood clearance. By conjugation of the GRPR antagonist RM26 (D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2) to an ABD (albumin-binding domain), we aimed to extend the blood circulation of peptides. The synthesized conjugate DOTA-ABD-RM26 was labelled with indium-111 and evaluated in vitro and in vivo. The labelled conjugate was stable in PBS and retained specificity and its antagonistic function against GRPR. The half-maximal inhibitory concentration (IC50) of In-nat-DOTA-ABD-RM26 in the presence of human serum albumin was 49 +/- 5 nM. [In-111]In-DOTA-ABD-RM26 had a significantly longer residence time in blood and in tumors (without a significant decrease of up to 144 h pi) than the parental RM26 peptide. We conclude that the ABD-RM26 conjugate can be used for GRPR-targeted therapy and delivery of cytotoxic drugs. However, the undesirable elevated activity uptake in kidneys abolishes its use for radionuclide therapy. This proof-of-principle study justified further optimization of the molecular design of the ABD-RM26 conjugate.

An important concern with using silicon nanoribbon field-effect transistors (SiNR FET) for ion-sensing is the pH-response of the gate oxide surface. Depending on the application of the FET sensor, this response has to be chemically manipulated. Thus in silicon oxide-gated pH-sensors with integrated sensor and reference FETS, a surface with high pH-sensitivity, compared to the bare gate oxide, is required in the sensor FETs (SEFET), whereas in the reference FETs (REFET) the surface has to be relatively pH-insensitive. In order to control the sensitivity and chemistry of the oxide surface of the nanoribbons, a silanization reagent with a functional group is often self-assembled on the SiNR surface. Choice of a silanization reaction that results in a self-assembled layer on a silicon oxide surface has been studied extensively over the past decades. However, the effect of various self-assembled layers such as monolayers or mixed layers on the electrical response of SiNR FETs in aqueous solution needs to be exploited further, especially for future integrated SEFET/REFET systems. In this work, we have performed a comprehensive study on 3-aminopropyltriethoxysilane (APTES) silanization of silicon oxide surfaces using microwave (MW) heating as a new biocompatible route to conventional methods. A set of complementary surface characterization techniques (ellipsometry, AFM and ATR-FTIR) was used to analyze the properties of the APTES layer deposited on the silicon surface. We have found that a uniform monolayer can be achieved within 10 min by heating the silanization solution to 75 degrees C using MW heating. Furthermore, electrical measurements suggest that little change in device performance is observed after exposure to MW irradiation. Real-time pH measurements indicate that a uniform APTES monolayer not only reduces the pH sensitivity of SiNR FET by passivating the surface silanol groups, but also makes the device less sensitive to cation concentration in the background electrolyte. Our silanization route proves promising for future chemical surface modification of on-chip REFETs.

Introduction We have previously developed a pretargeting approach for affibody-mediated cancer therapy based on PNA–PNA hybridization. In this article we have further developed this approach by optimizing the production of the primary agent, ZHER2:342-SR-HP1, and labeling the secondary agent, HP2, with the therapeutic radionuclide 177Lu. We also studied the biodistribution profile of 177Lu-HP2 in mice, and evaluated pretargeting with 177Lu-HP2 in vitro and in vivo. Methods The biodistribution profile of 177Lu-HP2 was evaluated in NMRI mice and compared to the previously studied 111In-HP2. Pretargeting using 177Lu-HP2 was studied in vitro using the HER2-expressing cell lines BT‐474 and SKOV-3, and in vivo in mice bearing SKOV-3 xenografts. Results and conclusion Using an optimized production protocol for ZHER2:342-SR-HP1 the ligation time was reduced from 15 h to 30 min, and the yield increased from 45% to 70%. 177Lu-labeled HP2 binds specifically in vitro to BT474 and SKOV-3 cells pre-treated with ZHER2:342-SR-HP1. 177Lu-HP2 was shown to have a more rapid blood clearance compared to 111In-HP2 in NMRI mice, and the measured radioactivity in blood was 0.22 ± 0.1 and 0.68 ± 0.07%ID/g for 177Lu- and 111In-HP2, respectively, at 1 h p.i. In contrast, no significant difference in kidney uptake was observed (4.47 ± 1.17 and 3.94 ± 0.58%ID/g for 177Lu- and 111In-HP2, respectively, at 1 h p.i.). Co-injection with either Gelofusine or lysine significantly reduced the kidney uptake for 177Lu-HP2 (1.0 ± 0.1 and 1.6 ± 0.2, respectively, vs. 2.97 ± 0.87%ID/g in controls at 4 h p.i.). 177Lu-HP2 accumulated in SKOV-3 xenografts in BALB/C nu/nu mice when administered after injection of ZHER2:342-SR-HP1. Without pre-injection of ZHER2:342-SR-HP1, the uptake of 177Lu-HP2 was about 90-fold lower in tumor (0.23 ± 0.08 vs. 20.7 ± 3.5%ID/g). The tumor-to-kidney radioactivity accumulation ratio was almost 5-fold higher in the group of mice pre-injected with ZHER2:342-SR-HP1. In conclusion, 177Lu-HP2 was shown to be a promising secondary agent for affibody-mediated tumor pretargeting in vivo.

Introduction: Affibody molecules have demonstrated potential for radionuclide molecular imaging. The aim of this study was to synthesize and evaluate a maleimido derivative of the 1,4,7-triazacyclononane-l-glutaric acid-4,7-diacetic acid (NODAGA) for site-specific labeling of anti-HER2 Affibody molecule. Methods: The maleimidoethylmonoamide NODAGA (MMA-NODAGA) was synthesized and conjugated to Z(HER2:2395) Affibody molecule having a C-terminal cysteine. Labeling efficiency, binding specificity to and cell internalization by HER2-expressing cells of [In-111-MMA-NODAGA-Cys(61)]-Z(HER2:2395) were studied. Biodistribution of [In-111-MMA-NODAGA-Cys(61)]-Z(HER2:2395) and [In-111-MMA-DOTA-Cys(61)]-Z(HER2:2395) was compared in mice. Results: The affinity of [MMA-NODAGA-Cys(61)]-Z(HER2:2395) binding to HER2 was 67 pM. The In-1111-labeling yield was 99.6%+/- 0.5% after 30 min at 60 degrees C. [In-111-MMA-NODAGA-Cys(61)]-Z(HER2:2395) bound specifically to HER2-expressing cells in vitro and in vivo. Tumor uptake of [In-111-MMA-NODAGA-Cys(61)]-ZHER(2:2395) in mice bearing DU-145 xenografts (4.7%+/- 0.8% ID/g) was lower than uptake of [In-111-MMA-DOTA-Cys(61)]-Z(HER2:2395) (7.5%+/- 1.6% ID/g). However, tumor-to-organ ratios were higher for [In-111-MMA-NODAGA-Cys(61)]-Z(HER2:2395) due to higher clearance rate from normal tissues. Conclusions: MMA-NODAGA is a promising chelator for site-specific labeling of targeting proteins containing unpaired cysteine. Appreciable influence of chelators on targeting properties of Affibody molecules was demonstrated.

Affibody molecules constitute a new class of probes for radionuclide tumor targeting. The small size of Affibody molecules is favorable for rapid localization in tumors and clearance from circulation. However, high renal reabsorption of Affibody molecules prevents the use of residualizing radiometals, including several promising low-energy (beta- and alpha-emitters, for radionuclide therapy. We tested a hypothesis that Affibody-based pretargeting mediated by a bioorthogonal interaction between trans-cyclooctene (TCO) and tetrazine would provide higher accumulation of radiometals in tumor xenografts than in the kidneys. Methods: TCO was conjugated to the anti-human epidermal growth factor receptor 2 (HER2) Affibody molecule Z(2395). DOTA-tetrazine was labeled with In-111 and Lu-177. In vitro pretargeting was studied in HER2-expressing SKOV-3 and BT474 cell lines. In vivo studies were performed on BALB/C nu/nu mice bearing SKOV-3 xenografts. Results: I-125-Z(2395)-TCO bound specifically to HER2-expressing cells in vitro with an affinity of 45 +/- 16 pM. In-111-tetrazine bound specifically and selectively to Z(2325)-TCO pretreated cells. In vivo studies demonstrated HER2-specific I-125-Z(2395)-TCO accumulation in xenografts. TCO-mediated In-111-tetrazine localization was shown in tumors, when the radiolabeled tracer was injected 4 h after an injection of Z(2395)-TCO. At 1 h after injection, the tumor uptake of In-111-tetrazine and Lu-177-tetrazine was approximately 2-fold higher than the renal uptake. Pretargeting provided more than a 56-fold reduction of renal uptake of In-111 in comparison with direct targeting. Conclusion: The feasibility of Affibody-based bioorthogonal chemistry-mediated pretargeting was demonstrated. The use of pre-targeting provides a substantial reduction of radiometal accumulation in kidneys, creating preconditions for palliative radionuclide therapy.

Accurate detection of cancer-associated molecular abnormalities in tumors could make cancer treatment more of personalized. Affibody molecules enable high contrast imaging of tumor-associated protein expression shortly after injection. The use should increase sensitivity of HER2 imaging. The chemical nature of the generator-produced positron-emitting radionuclide Ga-68 of radionuclides and chelators influences the biodistribution of Affibody molecules, providing an opportunity to further increase the imaging contrast. The aim of the study was to compare maleimido derivatives of DOTA and NODAGA for site-specific labeling of a recombinant Z(HER2:2395) HER2-binding Affibody molecule with Ga-68. DOTA and NODAGA were site-specifically conjugated to the Z(HER2:2395) Affibody molecule having a C-terminal cysteine and labeled with Ga-68 and In-111. All labeled conjugates retained specificity to HER2 in vitro. Most of the cell-associated activity was membrane-bound with a minor difference in internalization rate. All variants demonstrated specific targeting of xenografts and a high tumor uptake. The xenografts were dearly visualized using all conjugates. The influence of chelator on the biodistribution and targeting properties was much less pronounced for Ga-68 than for In-111. The tumor uptake of Ga-68-NODAGA-Z(HER2:2395) and Ga-68-NODAGA-Z(HER2:2395) and tumor-to-blood ratios at 2 h p.i. did not differ significantly. However, the tumor-to-liver ratio was significantly higher for Ga-68-NODAGA- Z(HER2:2395) (8 +/- 2 vs 5.0 +/- 0.3) offering the advantage of better liver metastases visualization. In conclusion, influence of chelators on biodistribution of Affibody molecules depends on the radionuclides and reoptimization of labeling chemistry is required when a radionuclide label is changed.

Affibody molecules are small engineered scaffold proteins suitable for in vivo tumor targeting. Radionuclide molecular imaging using directly radiolabelled affibody molecules provides excellent imaging. However, affibody molecules have a high renal reabsorption, which complicates their use for radionuclide therapy. The high renal reabsorption is a common problem for the use of engineered scaffold proteins for radionuclide therapy. Affibody-based PNA-mediated pretargeting reduces dramatically the absorbed dose to the kidneys and makes affibody-based radionuclide therapy possible. This methodology might, hopefully, solve the problem of high renal reabsorption for radionuclide therapy mediated by other engineered scaffold proteins. 

Small extracellular vesicles (sEVs) have in recent years evolved as a source of biomarkers for disease diagnosis and therapeutic follow up. sEV samples derived from multicellular organisms exhibit a high heterogeneous repertoire of vesicles which current methods based on ensemble measurements cannot capture. In this work we present droplet barcode sequencing for protein analysis (DBS-Pro) to profile surface proteins on individual sEVs, facilitating identification of sEV-subtypes within and between samples. The method allows for analysis of multiple proteins through use of DNA barcoded affinity reagents and sequencing as readout. High throughput single vesicle profiling is enabled through compartmentalization of individual sEVs in emulsion droplets followed by droplet barcoding through PCR. In this proof-of-concept study we demonstrate that DBS-Pro allows for analysis of single sEVs, with a mixing rate below 2%. A total of over 120,000 individual sEVs obtained from a NSCLC cell line and from malignant pleural effusion (MPE) fluid of NSCLC patients have been analyzed based on their surface proteins. We also show that the method enables single vesicle surface protein profiling and by extension characterization of sEV-subtypes, which is essential to identify the cellular origin of vesicles in heterogenous samples.

DNA microarray technology has evolved dramatically in recent years, and is now a common tool in researchers portfolios. The scope of the technique has expanded from small-scale studies to extensive studies such as classification of disease states. Technical knowledge regarding solid phase microarrays has also increased, and the results acquired today are more reliable than those obtained just a few years ago. Nevertheless, there are various aspects of microarray analysis that could be improved. In this article we show that the proportions of full-length probes used significantly affects the results of global analyses of transcriptomes. In particular, measurements of transcripts in low abundance are more sensitive to truncated probes, which generally increase the degree of cross hybridization and loss of specific signals. In order to improve microarray analysis, we here introduce a disiloxyl purification step, which ensures that all the probes on the microarray are at full length. We demonstrate that when the features on microarrays consist of full-length probes the signal intensity is significantly increased. The overall increase in intensity enables the hybridization stringency to be increased, and thus enhance the robustness of the results.

NOVELTY - A pre-targeting system comprising an anti-cluster of differentiation (CD)38 single-domain antibody (sdAb) and a second agent capable of specifically binding to the anti-CD38 sdAb and comprising a second molecule is new, where the antibody comprises an amino acid sequence that comprises 3 complementary determining regions (CDR1-CDR3). The CDR1 is chosen from (a) an amino acid sequence of SEQ ID NO: 1, (b) polypeptides that have at least 80% amino acid sequence identity with SEQ ID NO: 1, and (c) polypeptides that have 3, 2 or 1 amino acid difference with SEQ ID NO: 1. The CDR2 is chosen from (a) an amino acid sequence of SEQ ID NO: 2, (b) polypeptides that have at least 80% amino acid sequence identity with SEQ ID NO: 2, (c) polypeptides that have 3, 2 or 1 amino acid difference with SEQ ID NO: 2.

USE - The pre-targeting system is useful in kit of parts or medicine or diagnostics for diagnosing, monitoring and treating neoplastic disease in subject, and evaluating or monitoring presence, location and/or amount of CD38-expressing cells in subject. The neoplastic disease is a solid tumor. The neoplastic disease is hepatocellular carcinoma, lung cancer, melanoma, breast cancer or glioma, preferably hematological malignancy. The neoplastic disease is multiple myeloma, non-Hodgkin lymphoma (NHL) or chronic lymphoid leukemia (CLL), preferably multiple myeloma (all claimed).

ADVANTAGE - The system exhibits excellent cytotoxic effect on CD38-expressing neoplastic cells.

DETAILED DESCRIPTION - A pre-targeting system comprising an anti-cluster of differentiation (CD)38 single-domain antibody (sdAb) and a second agent capable of specifically binding to the anti-CD38 sdAb and comprising a second molecule is new, where the antibody comprises an amino acid sequence that comprises 3 complementary determining regions (CDR1-CDR3). The CDR1 is chosen from (a) an amino acid sequence of SEQ ID NO: 1, (b) polypeptides that have at least 80% amino acid sequence identity with SEQ ID NO: 1, and (c) polypeptides that have 3, 2 or 1 amino acid difference with SEQ ID NO: 1. The CDR2 is chosen from (a) an amino acid sequence of SEQ ID NO: 2, (b) polypeptides that have at least 80% amino acid sequence identity with SEQ ID NO: 2, (c) polypeptides that have 3, 2 or 1 amino acid difference with SEQ ID NO: 2. The CDR3 is chosen from (a) a 18 amino acid sequence (SEQ ID NO: 3) fully defined in the specification, (b) polypeptides that have at least 80% amino acid sequence identity with SEQ ID NO: 3, and (c) polypeptides that have 3, 2 or 1 amino acid difference with SEQ ID NO: 3. Tyr-Thr-Asp-Ser-Asp-Tyr-Ile (SEQ ID NO: 1), and Thr-Ile-Tyr-Ile-Gly-Gly-Thr-Tyr-Ile-His (SEQ ID NO: 2).

INDEPENDENT CLAIMS are included for the following:

• kit of parts comprising the pre-targeting system;
• use of pre-targeting system or kit of parts in medicine or diagnostics for diagnosing, monitoring and treating a neoplastic disease in a subject; and
• imaging method for evaluating or monitoring presence, location and/or amount of CD38-expressing cells in a subject involves (i) detecting, in a subject to whom a detectable quantity of the pre-targeting system, and (ii) generating an image representative of the location and/or quantity or intensity of the signal, where the second agent comprises a signal-emitting molecule, has been administered, signal emitted by said signal-emitting molecule.

Radioimmunotherapy (RIT) is a cancer treatment that combines radiation therapy with tumor-directed monoclonal antibodies (Abs). Although RIT had been introduced for the treatment of CD20 positive non-Hodgkin lymphoma decades ago, it never found a broad clinical application. In recent years, researchers have developed theranostic agents based on Ab fragments or small Ab mimetics such as peptides, affibodies or single-chain Abs with improved tumor-targeting capacities. Theranostics combine diagnostic and therapeutic capabilities into a single pharmaceutical agent; this dual application can be easily achieved after conjugation to radionuclides. The past decade has seen a trend to increased specificity, fastened pharmacokinetics, and personalized medicine. In this review, we discuss the different strategies introduced for the noninvasive detection and treatment of hematological malignancies by radiopharmaceuticals. We also discuss the future applications of these radiotheranostic agents.

Small extracellular vesicles (sEVs) generated from the endolysosomal system, often referred to as exosomes, have attracted interest as a suitable biomarker for cancer diagnostics, as they carry valuable biological information and reflect their cells of origin. Herein, we propose a simple and inexpensive electrical method for label-free detection and profiling of sEVs in the size range of exosomes. The detection method is based on the electrokinetic principle, where the change in the streaming current is monitored as the surface markers of the sEVs interact with the affinity reagents immobilized on the inner surface of a silica microcapillary. As a proof-of-concept, we detected sEVs derived from the non-small-cell lung cancer (NSCLC) cell line H1975 for a set of representative surface markers, such as epidermal growth factor receptor (EGFR), CD9, and CD63. The detection sensitivity was estimated to be similar to 175000 sEVs, which represents a sensor surface coverage of only 0.04%. We further validated the ability of the sensor to measure the expression level of a membrane protein by using sEVs displaying artificially altered expressions of EGFR and CD63, which were derived from NSCLC and human embryonic kidney (HEK) 293T cells, respectively. The analysis revealed that the changes in EGFR and CD63 expressions in sEVs can be detected with a sensitivity in the order of 10% and 3%, respectively, of their parental cell expressions. The method can be easily parallelized and combined with existing microfluidic-based EV isolation technologies, allowing for rapid detection and monitoring of sEVs for cancer diagnosis.

This paper reports on a two-terminal silicon nanoribbon (SiNR) field-effect pH sensor operated in electrolyte. Observed experimentally and confirmed by modeling, the sensor is activated by self-gating with a gate bias set by the potential difference of the two terminals. The effect of this gate bias on the SiNR conductance is modulated by the potential drop over the electrical double layer (EDL) established on the SiNR surface, similarly to the threshold voltage modulation by EDL in a three-terminal SiNR field-effect transistor with an independent gate electrode. The potential drop over EDL is determined by the pH value of the electrolyte.

Current instability is observed for silicon nanowire field-effect transistors operating in electrolytes with Pt gate electrodes. A comparative study involving an Ag/AgCl-reference gate electrode reveals that the effect results from a drift in the potential at the Pt-electrode/electrolyte interface. In a phosphate buffer saline of pH 7.4, the stabilization of the potential of the Pt electrode was found to require approximately 1000 s. A concurrent potential drift, with a comparable time constant, occurring at the electrolyte/oxidized-nanowire interface rendered a complex device current response which complicated the interpretation of the results.

Purpose: Site-specific approaches to bioconjugation produce well-defined and homogeneous immunoconjugates with potential for superior in vivo behavior compared to analogs synthesized using traditional, stochastic methods. The possibility of incorporating photoaffinity chemistry into a site-specific bioconjugation strategy is particularly enticing, as it could simplify and accelerate the preparation of homogeneous immunoconjugates for the clinic. In this investigation, we report the synthesis, in vitro characterization, and in vivo evaluation of a site-specifically modified, 89Zr-labeled radioimmunoconjugate created via the reaction between an mAb and an Fc-binding protein bearing a photoactivatable 4-benzoylphenylalanine residue. Procedures: A variant of the Fc-binding Z domain of protein A containing a photoactivatable, 4-benzoylphenylalanine residue — Z(35BPA) — was modified with desferrioxamine (DFO), combined with the A33 antigen-targeting mAb huA33, and irradiated with UV light. The resulting immunoconjugate — DFOZ(35BPA)-huA33 — was purified and characterized via SDS-PAGE, MALDI-ToF mass spectrometry, surface plasmon resonance, and flow cytometry. The radiolabeling of DFOZ(35BPA)-huA33 was optimized to produce [89Zr]Zr-DFOZ(35BPA)-huA33, and the immunoreactivity of the radioimmunoconjugate was determined with SW1222 human colorectal cancer cells. Finally, the in vivo performance of [89Zr]Zr-DFOZ(35BPA)-huA33 in mice bearing subcutaneous SW1222 xenografts was interrogated via PET imaging and biodistribution experiments and compared to that of a stochastically labeled control radioimmunoconjugate, [89Zr]Zr-DFO-huA33. Results: HuA33 was site-specifically modified with Z(35BPA)-DFO, producing an immunoconjugate with on average 1 DFO/mAb, high in vitro stability, and high affinity for its target. [89Zr]Zr-DFOZ(35BPA)-huA33 was synthesized in 95% radiochemical yield and exhibited a specific activity of 2 mCi/mg and an immunoreactive fraction of ~ 0.85. PET imaging and biodistribution experiments revealed that high concentrations of the radioimmunoconjugate accumulated in tumor tissue (i.e., ~ 40%ID/g at 120 h p.i.) but also that the Z(35BPA)-bearing immunoPET probe produced higher uptake in the liver, spleen, and kidneys than its stochastically modified cousin, [89Zr]Zr-DFO-huA33. Conclusions: Photoaffinity chemistry and an Fc-binding variant of the Z domain were successfully leveraged to create a novel site-specific strategy for the synthesis of radioimmunoconjugates. The probe synthesized using this method — DFOZ(35BPA)-huA33 — was well-defined and homogeneous, and the resulting radioimmunoconjugate ([89Zr]Zr-DFOZ(35BPA)-huA33) boasted high specific activity, stability, and immunoreactivity. While the site-specifically modified radioimmunoconjugate produced high activity concentrations in tumor tissue, it also yielded higher uptake in healthy organs than a stochastically modified analog, suggesting that optimization of this system is necessary prior to clinical translation.

We present a simple and inexpensive method for label-free detection of biomolecules. The method monitors the changes in streaming current in a fused silica capillary as target biomolecules bind to immobilized receptors on the inner surface of the capillary. To validate the concept, we show detection and time response of different protein-ligand and protein-protein systems: biotin-avidin and biotin-streptavidin, barstar-dibarnase and Z domain-immunoglobulin G (IgG). We show that specific binding of these biomolecules can be reliably monitored using a very simple setup. Using sequential injections of various proteins at a diverse concentration range and as well as diluted human serum we further investigate the capacity of the proposed technique to perform specific target detection from a complex sample. We also investigate the time for the signal to reach equilibrium and its dependence on analyte concentration and demonstrate that the current setup can be used to detect biomolecules at a concentration as low as 100 pM without requiring any advanced device fabrication procedures. Finally, an analytical model based on diffusion theory has been presented to explain the dependence of the saturation time on the analyte concentration and capillary dimensions and how reducing length and inner diameter of the capillary is predicted to give faster detection and in practice also lower limit of detection.

Affibody molecules represent a novel class of affinity proteins with a high potential as tracers for radio-nuclide molecular imaging. In this comparative structure-property study, a series of Affibody molecules with the Tc-99m-chelators maGGG, maSSS, or maESE attached to the e-amine of the internally positioned K49 was prepared by peptide synthesis, for comparison to molecules with similar chelators positioned at the N-terminus. The conjugates were labeled with Tc-99m and evaluated in vitro and in vivo. It was found that both composition and position of the chelating moiety influence the label stability, biodistribution and targeting properties of HER2-binding Affibody molecules.

The human epidermal growth factor receptor HER2 has emerged as an important target for molecular imaging of breast cancer. This article presents the design and synthesis of a HER2-targeting affibody molecule with improved stability and tumor targeting capacity and with potential use as an imaging agent. The 58 aa three-helix bundle protein was assembled using solid-phase peptide synthesis, and a chemoselective ligation strategy was used to establish an intramolecular thioether bond between the side chain thiol group of a cysteine residue, positioned in the loop between helices I and II, and a chloroacetyl group on the side chain amino group of the C-terminal lysine residue. The tethered protein offered an increased thermal stability, with a melting temperature of 64 degrees C, compared to 54 degrees C for the linear control. The ligation did not have a major influence on the HER2 binding affinity, which was 320 and 380 pM for the crosslinked and linear molecules, respectively. Biodistribution studies were performed both in normal and tumor-bearing mice to evaluate the impact of the crosslinking on the in vivo behavior and on the tumor targeting performance. The distribution pattern was characterized by a low uptake in all organs except kidney, and rapid clearance from blood and normal tissue. Crosslinking of the protein resulted in a significantly increased tumor accumulation, rendering the tethered HER2-binding affibody molecule a valuable lead in the development of superior HER2 imaging agents.

Purpose  Affibody molecules are low molecular weight proteins (7 kDa), which can be selected to bind to tumour-associated target proteins with subnanomolar affinity. Because of rapid tumour localisation and clearance from nonspecific compartments, Affibody molecules are promising tracers for molecular imaging. Earlier, ^99mTc-labelled Affibody molecules demonstrated specific targeting of tumour xenografts. However, the biodistribution was suboptimal either because of hepatobiliary excretion or high renal uptake of the radioactivity. The goal of this study was to optimise the biodistribution of Affibody molecules by chelator engineering. Materials and methods  Anti-HER2 Z_HER2:342 Affibody molecules, carrying the mercaptoacetyl-glutamyl-seryl-glutamyl (maESE), mercaptoacetyl-glutamyl-glutamyl-seryl (maEES) and mercaptoacetyl-seryl-glutamyl-glutamyl (maSEE) chelators, were prepared by peptide synthesis and labelled with ^99mTc. The tumour-targeting capacity of these conjugates was compared with each other and with the best previously available conjugate, ^99mTc-maEEE-Z_HER2:342, in nude mice bearing SKOV-3 xenografts. The tumour-targeting capacity of the most promising conjugate, ^99mTc-maESE-Z_HER2:342, was compared with radioiodinated Z_HER2:342. Results  All novel conjugates demonstrated successful tumour targeting and a low degree of hepatobiliary excretion. The renal uptakes of serine-containing conjugates, 33 ± 5, 68 ± 21 and 71 ± 10%IA/g, for^99mTc-maESE-Z_HER2:342, ^99mTc-maEES-Z_HER2:342 and ^99mTc-maSEE-Z_HER2:342, respectively, were significantly reduced in comparison with ^99mTc-maEEE-Z_HER2:342 (102 ± 13%IA/g). For ^99mTc-maESE-Z_HER2:342, a tumour uptake of 9.6 ± 1.8%IA/g and a tumour-to-blood ratio of 58 ± 6 were reached at 4 h p.i. Conclusions  A combination of serine and glutamic acid residues in the chelator sequence confers increased renal excretion and relatively low renal uptake of ^99mTc-labelled Affibody molecules. In combination with preserved targeting capacity, this improved imaging of targets in abdominal area.

Direct electrical detection of biomolecules at high sensitivity hat recently been demonstrated using semiconductor nanowires. Here we demonstrate that semiconductor nanoribbons, in this case, a thin sheet of silicon on an oxidized silicon substrate, can approach the same sensitivity extending below the picomolar concentration regime in the biotin/streptavidin case. This corresponds to less than similar to 20 analyte molecules bound to receptors on the nanoribbon surface. The micrometer-size lateral dimensions of the nanoribbon enable optical lithography to be used, resulting in a simple and high-yield fabrication process. Electrical characterization of the nanoribbons is complemented by computer simulations showing enhanced sensitivity for thin ribbons. Finally, we demonstrate that the device can be operated both in inversion as well as in accumulation mode and the measured differences in detection sensitivity are explained in terms of the distance between the channel and the receptor coated surface with respect to the Debye screening length. The nanoribbon approach opens up for large scale CMOS fabrication of highly sensitive biomolecule sensor chips for potential use in medicine and biotechnology.

Silicon nanowires of different widths were fabricated in silicon on insulator (SOI) material using conventional process technology combined with electron-beam lithography. The aim was to analyze the size dependence of the sensitivity of such nanowires for biomolecule detection and for other sensor applications. Results from electrical characterization of the nanowires show a threshold voltage increasing with decreasing width. When immersed in an acidic buffer solution, smaller nanowires exhibit large conductance changes while larger wires remain unaffected. This behavior is also reflected in detected threshold shifts between buffer solutions of different pH, and we find that nanowires of width > 150 nm are virtually insensitive to the buffer pH. The increased sensitivity for smaller sizes is ascribed to the larger surface/volume ratio for smaller wires exposing the channel to a more effective control by the local environment, similar to a surrounded gate transistor structure. Computer simulations confirm this behavior and show that sensing can be extended even down to the single charge level.

Purpose  Expression of human epidermal growth factor receptor type 2 (HER2) in malignant tumours possesses well-documented prognostic and predictive value. Non-invasive imaging of expression can provide valuable diagnostic information, thereby influencing patient management. Previously, we reported a phage display selection of a small (about 7 kDa) protein, the Affibody molecule Z_HER2:342, which binds HER2 with subnanomolar affinity, and demonstrated the feasibility of targeting of HER2-expressing xenografts using radioiodinated Z_HER2:342. The goal of this study was to develop a method for ^99mTc labelling of Z_HER2:342 using the MAG3 chelator, which was incorporated into Z_HER2:342 using peptide synthesis, and evaluate the targeting properties of the labelled conjugate. Methods  MAG3-Z_HER2:342 was assembled using Fmoc/tBu solid phase peptide synthesis. Biochemical characterisation of the agent was performed using RP-HPLC, ESI-MS, biosensor studies and circular dichroism. A procedure for ^99mTc labelling in the presence of sodium/potassium tartrate was established. Tumour targeting was evaluated by biodistribution study and gamma camera imaging in xenograft-bearing mice. Biodistribution of ^99mTc-MAG3-Z_HER2:342 and ¹²⁵I-para-iodobenzoate -Z_HER2:342 was compared 6 h p.i. Results  Synthetic MAG3-Z_HER2:342 possessed an affinity of 0.2 nM for HER2 receptors. The peptide was labelled with ^99mTc with an efficiency of about 75–80%. Labelled ^99mTc-MAG3-Z_HER2:342 retained capacity to bind specifically HER2-expressing SKOV-3 cells in vitro. ^99mTc-MAG3-Z_HER2:342 showed specific tumour targeting with a contrast similar to a radioiodinated analogue in mice bearing LS174T xenografts. Gamma camera imaging demonstrated clear and specific visualisation of HER2 expression. Conclusion  Incorporation of a mercaptoacetyl-containing chelating sequence during chemical synthesis enabled site-specific ^99mTc labelling of the Z_HER2:342 Affibody molecule with preserved targeting capacity.

Site-specifically triple-labelled three-helix bundle affinity proteins (affibody molecules) have been produced by total chemical Synthesis. The 58 aa affinity proteins were assembled on an automated peptide synthesizer, followed by manual on-resin incorporation of three different reporter groups. An orthogonal protection strategy was developed for the site-specific introduction of 5-(2-aminethylamino)-1-nophthalenesulfonic acid (EDANS) and 6(7-nitrobenzofurazon-4-yiamino)-hexanoic acid (NBDX), constituting a donor/acceptor pair for fluorescence resonance energy transfer (FRET), and a biotin moiety, used for surface immobilization. Circular dichroism and biosensor studies of the synthetic proteins and their recombinant counterparts revealed that the synthetic proteins were folded and retained their binding specificities. The biotin-conjugated protein could be immobilized onto a streptavidin surface without loss of activity. The synthetic, doubly fluorescent-labelled affinity proteins were shown to function as fluorescent biosensors in an assay for the specific detection of unlabelled human IgG and IgA.

Purpose  Monitoring HER2 expression is crucial for selection of breast cancer patients amenable to HER2-targeting therapy. The Affibody molecule Z_HER2:342 binds to HER2 with picomolar affinity and enables specific imaging of HER2 expression. Previously, Z_HER2:342 with the additional N-terminal mercaptoacetyl-glycyl-glycyl-glycyl (maGGG) sequence was labelled with ^99mTc and demonstrated specific targeting of HER2-expressing xenografts. However, hepatobiliary excretion caused high radioactivity accumulation in the abdomen. We investigated whether the biodistribution of Z_HER2:342 can be improved by substituting glycyl residues in the chelating sequence with more hydrophilic seryl residues.

Methods  The Affibody molecule Z_HER2:342, carrying the chelators mercaptoacetyl-glycyl-seryl-glycyl (maGSG), mercaptoacetyl-glycyl-D-seryl-glycyl [maG(D-S)G] and mercaptoacetyl-seryl-seryl-seryl (maSSS), were prepared by peptide synthesis and labelled with ^99mTc. The differences in the excretion pathways were evaluated in normal mice. The tumour targeting capacity of ^99mTc-maSSS-Z_HER2:342 was studied in nude mice bearing SKOV-3 xenografts and compared with the capacity of radioiodinated Z_HER2:342.

Results  A shift towards renal excretion was obtained when glycine was substituted with serine in the chelating sequence. The radioactivity in the gastrointestinal tract was reduced threefold for the maSSS conjugate in comparison with the maGGG conjugate 4 h post injection (p.i.). The tumour uptake of ^99mTc-maSSS-Z_HER2:342 was 11.5 ± 0.5% IA/g 4 h p.i., and the tumour-to-blood ratio was 76. The pharmacokinetics and uptake characteristics of technetium-labelled Z_HER2:342 were better than those of radioiodinated Z_HER2:342.

Conclusion  The introduction of serine residues in the chelator results in better tumour imaging properties of the Affibody molecule Z_HER2:342 compared with glycyl-containing chelators and is favourable for imaging of tumours and metastases in the abdominal area.

Pretargeting is a strategy to improve the tumor-to-healthy tissue contrast in targeted nuclear imaging and therapy. The strategy relies on separating the tumor-targeting agent from the radioactive payload and combine the two in vivo. In the pretargeting approach previously studied by our group, the tumor targeting was mediated by an Affibody functionalized with a peptide nucleic acid (PNA) probe and the radionuclide was carried by a complementary PNA probe. Affibody-mediated PNA-based pretargeting was shown to increase the tumor-to-kidney ratio when evaluated in HER2-overexpressing tumor-bearing mice. The aim of the current study is to further optimize the design of the PNA probes to achieve better biodistribution properties and preconditions for a more cost-efficient production. The first important feature of the PNA pretargeting system is the tumor-to-kidney ratio, where the kidney retention is the dose-limiting factor for a clinical therapeutic application. The second aspect is the production of PNA, where the synthesis of PNA strands can be a challenge due to the steric repulsion between two PNA residues’ side chain and poor solubility in the synthesis solvent. In order to simplify the synthesis, we optimized the automation of the process using a microwave-assisted peptide synthesizer. Once the automated synthesis protocols were set up, we designed and synthesized a panel of new PNA probes, aimed at reducing the length of the PNA strands. The reduction in length was expected to simplify the synthesis workflow, but also to possibly decrease the kidney retention of the radioactive payload, as was shown in a previous study when reducing the length of the secondary PNA strand could improve the tumor-to-kidney ratio. The PNA duplexes were studied by CD and UV spectroscopy, and the binding kinetics of the interaction were studied by SPR to identify the limit in terms of number of base pairs needed to reach the high affinity expected to be required for an efficient pretargeting system. Our results showed that high affinity duplexes are formed between PNA probes having only 8 to 9 complementary bases, but that PNA probes with 6 or 7 complementary bases give rise to less stable duplexes having lower melting temperatures and faster dissociation rates.

The present invention relates to site-specific labeling of antibodies or fragments thereof with one or more reporter group(s) in a way that does not affect antigen binding. The method for labeling antibodies and/or fragments thereof, comprises the following steps a) providing an IgG binding protein, which comprises [alpha]-helix structures, with a photoactivatable group and at least one label; b) forming a mixture of said IgG binding protein and the antibodies and/or fragments to be labeled; and c) UV illuminating said mixture for site-specific labeling of said antibodies and/or fragments thereof. The IgG binding protein is preferably the Z domain of Protein A.

Affibody molecules, small (7 kDa) scaffold proteins, are a promising class of probes for radionuclide molecular imaging. Radiolabeling of Affibody molecules with the positron-emitting nuclide 68Ga would permit the use of positron emission tomography (PET), providing better resolution, sensitivity, and quantification accuracy than single-photon emission computed tomography (SPECT). The synthetic anti-HER2 ZHER2:S1 Affibody molecule was conjugated with DOTA at the N-terminus, in the middle of helix 3, or at the Cterminus. The biodistribution of 68Ga-and 111In-labeled Affibody molecules was directly compared in NMRI nu/nu mice bearing SKOV3 xenografts. The position of the chelator strongly influenced the biodistribution of the tracers, and the influence was more pronounced for 68Ga-labeled Affibody molecules than for the 111In-labeled counterparts. The best 68Ga-labeled variant was 68Ga-[DOTA-A1]-ZHER2:S1, which provided a tumor uptake of 13 ± 1 %ID/g and a tumor to blood ratio of 39 ± 12 at 2 hours after injection. 111In-[DOTA-A1]-ZHER2:S1 and 111In-[DOTA-K58]-ZHER2:S1 were equally good at this time point, providing a tumor uptake of 15 to 16 %ID/g and a tumor to blood ratio in the range of 60 to 80. In conclusion, the selection of the best position for a chelator in Affibody molecules can be used for optimization of their imaging properties. This may be important for the development of Affibody-based and other protein-based imaging probes.

Introduction: Affibody molecules, small scaffold proteins, have demonstrated an appreciable potential as imaging probes. Affibody molecules are composed of three alpha-helices. Helices 1 and 2 are involved in molecular recognition, while helix 3 provides stability. The size of Affibody molecules can be reduced by omitting the third alpha-helix and cross-linking the two remaining, providing a smaller molecule with better extravasation and quicker clearance of unbound tracer. The goal of this study was to develop a novel 2-helix Affibody molecule based on backbone cyclization by native chemical ligation (NCL). Methods: The HER2-targeting NCL-cyclized Affibody molecule Z(HER2:342min) has been designed, synthesized and site-specifically conjugated with a DOTA chelator. DOTA-Z(HER2:342min) was labeled with In-111 and (68) Ga. The binding affinity of DOTA-Z(HER2:342min) was evaluated in vitro. The targeting properties of In-111- and (68) Ga-DOTA-Z(HER2:342min) were evaluated in mice bearing SKOV-3 xenografts and compared with the properties of In-111- and (68) Ga-labeled PEP09239, a DOTA-conjugated 2-helix Affibody analogue cyclized by a homocysteine disulfide bridge. Results: The dissociation constant (K-D) for DOTA-Z(HER2:342min) binding to HER2 was 18 nM according to SPR measurements. DOTA-Z(HER2:342min) was labeled with In-111 and (68) Ga. Both conjugates demonstrated bi-phasic binding kinetics to HER2-expressing cells, with K-D1 in low nanbmolar range. Both variants demonstrated specific uptake in HER2-expressing xenografts. Tumor-to-blood ratios at 2 h p.i. were 6.1 +/- 1.3 for In-111-DOTA-Z(HER2:342min) and 4.6 +/- 0.7 for (68) Ga-DOTA-Z(HER2:342min). However, the uptake of DOTA-Z(HER2:342min) in lung, liver and spleen was appreciably higher than the uptake of PEP09239-based counterparts. Conclusions: Native chemical ligation enables production of a backbone-cyclized HER2-binding 2-helix Affibody molecule (Z(HER2:342min)) with low nanomolar target affinity and specific tumor uptake.

Introduction: Affibody molecules are small (58 amino acids) high-affinity proteins based on a tri-helix nonimmunoglobulin scaffold. A clinical study has demonstrated that PET imaging using Affibody molecules labeled with Ga-68 (T-1/2 = 68 min) can visualize metastases of breast cancer expressing human epidermal growth factor receptor type 2 (HER2) and provide discrimination between tumors with high and low expression level. This may help to identify breast cancer patients benefiting from HER2-targeting therapies. The best discrimination was at 4 h post injection. Due to longer half-life, a positron-emitting radionuclide Sc-44 (T-1/2 = 4.04 h) might be a preferable label for Affibody molecules for imaging at several hours after injection. Methods: A synthetic second-generation anti-HER2 Affibody molecule Z(HER2:2891) was labeled with Sc-44 via a DOTA-chelator conjugated to the N-terminal amino group. Binding specificity, affinity and cellular processing Sc-44-DOTA-Z(HER2:2891) and Ga-68-DOTA-Z(HER2:2891) were compared in vitro using HER2-expressing cells. Biodistribution and imaging properties of Sc-44-DOTA-Z(HER2,2891) and Ga-68-DOTA-Z(HER2:2891) were evaluated in Balb/c nude mice bearing HER2-expression xenografts. Results: The labeling yield of 98 +/- 2% and specific activity of 7.8 GBq/mu mol were obtained. The conjugate demonstrated specific binding to HER2-expressing SKOV3.ip cells in vitro and to SKOV3.ip xenografts in nude mice. The distribution of radioactivity at 3 h post injection was similar for Sc-44-DOTA-Z(HER2:2891) and Ga-68-DOTA-Z(HER2:2891), but the blood clearance of the Sc-44-labeled variant was slower and the tumor-to-blood ratio was reduced (15 +/- 2 for (SC)-S-44-DOTA-Z(HER2:2891) vs 46 +/- 9 for Ga-68-DOTA-Z(HER2.2891)). At 6 h after injection of Sc-44-DOTA-Z(HER2,2891) the tumor uptake was 8 +/- 2% IA/g and the tumor-to-blood ratio was 51 +/- 8. Imaging using small-animal PET/CT demonstrated that (SC)-S-44-DOTA-ZHER2,2891 provides specific and high-contrast imaging of HER2-expressing xenografts. Conclusion: The Sc-44- DOTA-Z(HER2:2891) Affibody molecule is a promising probe for imaging of HER2-expression in malignant tumors.

Affibody molecules are small (7 kDa), non-immunoglobulin scaffold proteins with a potential as targeting agents for radionuclide imaging of cancer. However, high renal re-absorption of Affibody molecules prevents their use for radionuclide therapy with residualizing radiometals. We hypothesized that the use of Affibody-based peptide nucleic acid (PNA)-mediated pretargeting would enable higher accumulation of radiometals in tumors than in kidneys. To test this hypothesis, we designed an Affibody-PNA chimera Z(HER2:342)-SR-HP1 containing a 15-mer HP1 PNA recognition tag and a complementary HP2 hybridization probe permitting labeling with both I-125 and In-111. In-111-Z(HER2:342)-SR-HP1 bound specifically to HER2-expressing BT474 and SKOV-3 cancer cells in vitro, with a K-D of 6+/-2 pM for binding to SKOV-3 cells. Specific high affinity binding of the radiolabeled complementary PNA probe In-111-/I-125-HP2 to Z(HER2:342)-SR-HP1 pre-treated cells was demonstrated. In-111-Z(HER2:342)-SR-HP1 demonstrated specific accumulation in SKOV-3 xenografts in BALB/C nu/nu mice and rapid clearance from blood. Pre-saturation of SKOV-3 with non-labeled anti-HER2 Affibody or the use of HER2-negative Ramos xenografts resulted in significantly lower tumor uptake of In-111-Z(HER2:342)-SR-HP1. The complementary PNA probe In-111/I-125-HP2 accumulated in SKOV-3 xenografts when Z(HER2:342)-SR-HP1 was injected 4 h earlier. The tumor accumulation of In-111/I-125-HP2 was negligible without Z(HER2:342)-SR-HP1 pre-injection. The uptake of In-111-HP2 in SKOV-3 xenografts was 19+/-2 % ID/g at 1 h after injection. The uptake in blood and kidneys was approximately 50- and 2-fold lower, respectively. In conclusion, we have shown that the use of Affibody-based PNA-mediated pretargeting enables specific delivery of radiometals to tumors and provides higher radiometal concentration in tumors than in kidneys.

A unique strategy for effective, versatile, and facile surface biofunctionalization employing a recombinant spider silk protein genetically functionalized with the antibody-binding Z domain (Z-4RepCT) is reported. It is demonstrated that Z-silk can be applied to a variety of materials and platform designs as a truly one-step and chemical-free surface modification that site specifically captures antibodies while simultaneously reducing nonspecific adsorption. As a model surface, SiO2 is used to optimize and characterize Z-silk performance compared to the Z domain immobilized by a standard silanization method. First, Z-silk adsorption is investigated and verified its biofunctionality in a long-term stability experiment. To assess the binding capacity and protein-protein interaction stability of Z-silk, the coating is used to capture human antibodies in various assay formats. An eightfold higher binding capacity and 40-fold lower detection limit are obtained in the immunofluorescence assay, and the complex stability of captured antibodies is shown to be improved by a factor of 20. Applicability of Z-silk to functionalize microfluidic devices is demonstrated by antibody detection in an electrokinetic microcapillary biosensor. To test Z-silk for biomarker applications, real-time detection and quantification of human immunoglobulin G are performed in a plasma sample and C1q capture from human serum using an anti-C1q antibody.

Proteins play a pivotal role in cellular function and heterogeneity. Understanding cellular diversity at the proteome level necessitates sensitive single-cell assays with high throughput. While current sequencing-based methods offer promise, they often face limitations, including reliance on expensive and inaccessible commercial platforms. Here, we have adopted the DBS-Pro method, utilizing site-specific oligonucleotide-conjugated antibodies, to analyze surface proteins in single cells. The method uses cheap degenerated barcode oligonucleotides and a simple microfluidics setup for cell encapsulation. A sample of PBMCs was examined using a panel targeting six separate immune cell markers. Using this panel we could quantify marker expression on 1,307 cells, identifying major immune cell lineages including CD4+ T-cells, CD8+ T-cells, monocytes, and B-cells. While recognizing the need for protocol improvements, our results present a promising approach for single-cell proteomics.