In situ Raman spectral observation of succinimide intermediates in amyloid fibrillation kinetics

Succinimide intermediates play the crucial role in the nucleation process for protein amyloid fibril formation, as they can usually induce a non-native conformation in a fraction of soluble proteins to render amyloidogenicity and neurotoxicity. Thus, in situ detection of succinimide intermediates during amyloid fibrillation kinetics is of considerable importance, albeit challenging, because these succinimides are generally unstable in physiological conditions. Here, we found an in situ Raman spectral fingerprint to trace the succinimide intermediates in amyloid fibril formation, wherein the carbonyl symmetric stretching of cyclic imide in the succinimide derivative is located at ca. 1790 cm-1. Using its intensity as an indicator of succinimide intermediates, we have in situ detected and unravelled the role of succinimide intermediates during the oligomer formation from the Bz-Asp-Gly-NH2 dipeptide or the amyloid fibrillation kinetics of lysozyme with thermal/acid treatment.

Discovery and Control of Succinimide Formation and Accumulation at Aspartic Acid Residues in The Complementarity-Determining Region of a Therapeutic Monoclonal Antibody

PURPOSE

Succinimide formation and isomerization alter the chemical and physical properties of aspartic acid residues in a protein. Modification of aspartic acid residues within complementarity-determining regions (CDRs) of therapeutic monoclonal antibodies (mAbs) can be particularly detrimental to the efficacy of the molecule. The goal of this study was to characterize the site of succinimide accumulation in the CDR of a therapeutic mAb and understand its effects on potency. Furthermore, we aimed to mitigate succinimide accumulation through changes in formulation.

METHODS

Accumulation of succinimide was identified through intact and reduced LC-MS mass measurements. A low pH peptide mapping method was used for relative quantitation and localization of succinimide formation in the CDR. Statistical modeling was used to correlate levels of succinimide with basic variants and potency measurements.

RESULTS

Succinimide accumulation in Formulation A was accelerated when stored at elevated temperatures. A strong correlation between succinimide accumulation in the CDR, an increase in basic charge variants, and a decrease in potency was observed. Statistical modeling suggest that a combination of ion exchange chromatography and potency measurements can be used to predict succinimide levels in a given sample. Reformulation of the mAb to Formulation B mitigates succinimide accumulation even after extended storage at elevated temperatures.

CONCLUSION

Succinimide formation in the CDR of a therapeutic mAb can have a strong negative impact on potency of the molecule. We demonstrate that thorough characterization of the molecule by LC-MS, ion exchange chromatography, and potency measurements can facilitate changes in formulation that mitigate succinimide formation and the corresponding detrimental changes in potency.

PIMT-Mediated Labeling of l-Isoaspartic Acid with Tris Facilitates Identification of Isomerization Sites in Long-Lived Proteins

Isomerization of individual residues in long-lived proteins (LLPs) is a subject of growing interest in connection with many age-related human diseases. When isomerization occurs in LLPs, it can lead to deleterious changes in protein structure, function, and proteolytic degradation. Herein, we present a novel labeling technique for rapid identification of l-isoAsp using the enzyme protein l-isoaspartyl methyltransferase (PIMT) and Tris. The succinimide intermediate formed during reaction of l-isoAsp-containing peptides with PIMT and S-adenosyl methionine (SAM) is reactive with Tris base and results in a Tris-modified aspartic acid residue with a mass shift of +103 Da. Tris-modified aspartic acid exhibits prominent and repeated neutral loss of water when subjected to collisional activation. In addition, another dissociation pathway regenerates the original peptide following loss of a characteristic mass shift. Furthermore, it is demonstrated that Tris modification can be used to identify sites of isomerization in LLPs from biological samples such as the lens of the eye. This approach simplifies identification by labeling isomerization sites with a tag that causes a mass shift and provides characteristic loss during collisional activation.

Rapidly Self-Deactivating and Injectable Succinyl Ester-Based Bioadhesives for Postoperative Antiadhesion

Postoperative adhesion not only causes severe complications for patients but also increases their economic burden. Injectable bioadhesives with adhesiveness to tissues can cover irregular wounds and stay stable in situ, which is a promising barrier for antiadhesion. However, the potential tissue adhesion caused by bioadhesives' indiscriminate adhesiveness between normal and wounded tissue is still a problem. Herein, by using poly(ethylene glycol) succinimidyl succinate (PEG-SS) and gelatin, a succinyl ester-based bioadhesive (SEgel) was fabricated with self-deactivating properties for postoperative antiadhesion. Because N-hydroxysuccinimide esters (NHS-esters) were used as the adhesive group, the bioadhesives' side in contact with the tissue built covalent anchors quickly to maintain the stability, but the superficial layer facing outward withstood fast hydrolysis and then lost its adhesion within minutes, avoiding the indiscriminate adhesiveness. In addition, because of the specific degradation behavior of succinyl ester, the SEgel with proper in vivo retention was achieved without the worry of causing foreign body reactions and unexpected tissue adhesion. Both the cecum-sidewall adhesion and hepatic adhesion models showed that the SEgel markedly reduced the severity of tissue adhesion. These results, together with the ease of the preparation process and well-proven biocompatibility of raw materials, revealed that the SEgel might be a promising solution for postoperative antiadhesion.

Near-Infrared Fluorescence Imaging of Carotid Plaques in an Atherosclerotic Murine Model

Successful imaging of atherosclerosis, one of the leading global causes of death, is crucial for diagnosis and intervention. Near-infrared fluorescence (NIRF) imaging has been widely adopted along with multimodal/hybrid imaging systems for plaque detection. We evaluate two macrophage-targeting fluorescent tracers for NIRF imaging (TLR4-ZW800-1C and Feraheme-Alexa Fluor 750) in an atherosclerotic murine cohort, where the left carotid artery (LCA) is ligated to cause stenosis, and the right carotid artery (RCA) is used as a control. Imaging performed on dissected tissues revealed that both tracers had high uptake in the diseased vessel compared to the control, which was readily visible even at short exposure times. In addition, ZW800-1C's renal clearance ability and Feraheme's FDA approval puts these two tracers in line with other NIRF tracers such as ICG. Continued investigation with these tracers using intravascular NIRF imaging and larger animal models is warranted for clinical translation.

Label-retention expansion microscopy

Expansion microscopy (ExM) increases the effective resolving power of any microscope by expanding the sample with swellable hydrogel. Since its invention, ExM has been successfully applied to a wide range of cell, tissue, and animal samples. Still, fluorescence signal loss during polymerization and digestion limits molecular-scale imaging using ExM. Here, we report the development of label-retention ExM (LR-ExM) with a set of trifunctional anchors that not only prevent signal loss but also enable high-efficiency labeling using SNAP and CLIP tags. We have demonstrated multicolor LR-ExM for a variety of subcellular structures. Combining LR-ExM with superresolution stochastic optical reconstruction microscopy (STORM), we have achieved molecular resolution in the visualization of polyhedral lattice of clathrin-coated pits in situ.

Internal Illumination to Overcome the Cell Density Limitation in the Scale-up of Whole-Cell Photobiocatalysis

Cyanobacteria have the capacity to use photosynthesis to fuel their metabolism, which makes them highly promising production systems for the sustainable production of chemicals. Yet, their dependency on visible light limits the cell-density, which is a challenge for the scale-up. Here, it was shown with the example of a light-dependent biotransformation that internal illumination in a bubble column reactor equipped with wireless light emitters (WLEs) could overcome this limitation. Cells of the cyanobacterium Synechocystis sp. PCC 6803 expressing the gene of the ene-reductase YqjM were used for the reduction of 2-methylmaleimide to (R)-2-methylsuccinimide with high optical purity (>99 % ee). Compared to external source of light, illumination by floating wireless light emitters allowed a more than two-fold rate increase. Under optimized conditions, product formation rates up to 3.7 mm h-1 and specific activities of up to 65.5 U gDCW -1 were obtained, allowing the reduction of 40 mm 2-methylmaleimide with 650 mg isolated enantiopure product (73 % yield). The results demonstrate the principle of internal illumination as a means to overcome the intrinsic cell density limitation of cyanobacterial biotransformations, obtaining high reaction rates in a scalable photobioreactor.

Tracking the Behavior of Monoclonal Antibody Product Quality Attributes Using a Multi-Attribute Method Workflow

The multi-attribute method (MAM) is a liquid chromatography-mass spectrometry based method that is used to directly characterize and monitor many product quality attributes and impurities on biotherapeutics, most commonly at the peptide level. It utilizes high-resolution accurate mass spectral data which are analyzed in an automated fashion. MAM is a promising approach that is intended to replace or supplement several conventional assays with a single LC-MS analysis and can be implemented in a Current Good Manufacturing Practice environment. MAM provides accurate site-specific quantitation information on targeted attributes and the nontargeted new peak detection function allows to detect new peaks as impurities, modifications, or sequence variants when comparing to a reference sample. The high resolution MAM workflow was applied here for three independent case studies. First, to monitor the behavior of monoclonal antibody product quality attributes over the course of a 12-day cell culture experiment providing an insight into the behavior and dynamics of product attributes throughout the process. Second, the workflow was applied to test the purity and identity of a product through analysis of samples spiked with host cell proteins. Third, through the comparison of a drug product and a biosimilar with known sequence variants. The three case studies presented here, clearly demonstrate the robustness and accuracy of the MAM workflow that implies suitability for deployment in the regulated environment.

Synthesis and kinetic characterization of hyperbolic inhibitors of human cathepsins K and S based on a succinimide scaffold

Cathepsins K and S are closely related papain-like cysteine peptidases and potential therapeutic targets for metabolic and inflammatory diseases such as osteoporosis and arthritis. Here we describe the reduction of a previously characterized succinimide (2,5-dioxopyrrolidine)-containing hyperbolic inhibitor of cathepsin K (methyl (RS)-N-[1-(4-methoxyphenyl)-2,5-dioxopyrrolidin-3-yl]glycinate), to obtain a better and more selective compound (compound 4a - methyl (2,5-dioxopyrrolidin-3-yl)glycinate), which acted as a hyperbolic mixed inhibitor/activator similar to already known allosteric effectors of cathepsin K. We then investigated the potential of the succinimide scaffold as inhibitors of cathepsins K and/or S and synthesized a library of such compounds by 1,4-addition of α-amino acid esters and related compounds to N-substituted maleimides. From the generated library, we identified the first small molecule hyperbolic inhibitors of cathepsin S (methyl ((R)-2,5-dioxopyrrolidin-3-yl)-l-threoninate (compound R-4c) and 3-{[(1S,2R,3'S)-2-hydroxycyclohexyl]amino}pyrrolidine-2,5-dione (compound (1S,2R,3'S-10)). The former acted via a similar mechanism to compound 4a, while the latter was a hyperbolic specific inhibitor of cathepsin S. Given the versatility of the scaffold, the identified compounds will be used as the basis for the development of high-affinity hyperbolic inhibitors of the individual peptidases and to explore the potential of hyperbolic inhibitors for the inhibition of cysteine cathepsins in in vitro models.

Ex vivo evaluation of a multilayered sealant patch for watertight dural closure: cranial and spinal models

Cerebrospinal fluid leakage is a frequent complication after cranial and spinal surgery. To prevent this complication and seal the dura watertight, we developed Liqoseal, a dural sealant patch comprising a watertight polyesterurethane layer and an adhesive layer consisting of poly(DL-lactide-co-ε-caprolactone) copolymer and multiarmed N-hydroxylsuccinimide functionalized polyethylene glycol. We compared acute burst pressure and resistance to physiological conditions for 72 h of Liqoseal, Adherus, Duraseal, Tachosil, and Tisseel using computer-assisted models and fresh porcine dura. The mean acute burst pressure of Liqoseal in the cranial model (145 ± 39 mmHg) was higher than that of Adherus (87 ± 47 mmHg), Duraseal (51 ± 42 mmHg) and Tachosil (71 ± 16 mmHg). Under physiological conditions, cranial model resistance test results showed that 2 of 3 Liqoseal sealants maintained dural attachment during 72 hours as opposed to 3 of 3 for Adherus and Duraseal and 0 of 3 for Tachosil. The mean burst pressure of Liqoseal in the spinal model (233 ± 81 mmHg) was higher than that of Tachosil (123 ± 63 mmHg) and Tisseel (23 ± 16 mmHg). Under physiological conditions, spinal model resistance test results showed that 2 of 3 Liqoseal sealants maintained dural attachment for 72 hours as opposed to 3 of 3 for Adherus and 0 of 3 for Duraseal and Tachosil. This novel study showed that Liqoseal is capable of achieving a strong watertight seal over a dural defect in ex vivo models.

Increasing salinity of fibrinogen solvent generates stable fibrin hydrogels for cell delivery or tissue engineering

Fibrin has been used clinically for wound coverings, surgical glues, and cell delivery because of its affordability, cytocompatibility, and ability to modulate angiogenesis and inflammation. However, its rapid degradation rate has limited its usefulness as a scaffold for 3D cell culture and tissue engineering. Previous studies have sought to slow the degradation rate of fibrin with the addition of proteolysis inhibitors or synthetic crosslinkers that require multiple functionalization or polymerization steps. These strategies are difficult to implement in vivo and introduce increased complexity, both of which hinder the use of fibrin in research and medicine. Previously, we demonstrated that additional crosslinking of fibrin gels using bifunctionalized poly(ethylene glycol)-n-hydroxysuccinimide (PEG-NHS) slows the degradation rate of fibrin. In this study, we aimed to further improve the longevity of these PEG-fibrin gels such that they could be used for tissue engineering in vitro or in situ without the need for proteolysis inhibitors. It is well documented that increasing the salinity of fibrin precursor solutions affects the resulting gel morphology. Here, we investigated whether this altered morphology influences the fibrin degradation rate. Increasing the final sodium chloride (NaCl) concentration from 145 mM (physiologic level) to 250 mM resulted in fine, transparent high-salt (HS) fibrin gels that degrade 2–3 times slower than coarse, opaque physiologic-salt (PS) fibrin gels both in vitro (when treated with proteases and when seeded with amniotic fluid stem cells) and in vivo (when injected subcutaneously into mice). Increased salt concentrations did not affect the viability of encapsulated cells, the ability of encapsulated endothelial cells to form rudimentary capillary networks, or the ability of the gels to maintain induced pluripotent stem cells. Finally, when implanted subcutaneously, PS gels degraded completely within one week while HS gels remained stable and maintained viability of seeded dermal fibroblasts. To our knowledge, this is the simplest method reported for the fabrication of fibrin gels with tunable degradation properties and will be useful for implementing fibrin gels in a wide range of research and clinical applications.

Mannosylated Cationic Copolymers for Gene Delivery to Macrophages

Macrophages are desirable targets for gene therapy of cancer and other diseases. Cationic diblock copolymers of polyethylene glycol (PEG) and poly-L-lysine (PLL) or poly{N-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} (pAsp(DET)) are synthesized and used to form polyplexes with a plasmid DNA (pDNA) that are decorated with mannose moieties, serving as the targeting ligands for the C type lectin receptors displayed at the surface of macrophages. The PEG-b-PLL copolymers are known for its cytotoxicity, so PEG-b-PLL-based polyplexes are cross-linked using reducible reagent dithiobis(succinimidyl propionate) (DSP). The cross-linked polyplexes display low toxicity to both mouse embryonic fibroblasts NIH/3T3 cell line and mouse bone marrow-derived macrophages (BMMΦ). In macrophages mannose-decorated polyplexes demonstrate an ≈8 times higher transfection efficiency. The cross-linking of the polyplexes decrease the toxicity, but the transfection enhancement is moderate. The PEG-b-pAsp(DET) copolymers display low toxicity with respect to the IC-21 murine macrophage cell line and are used for the production of non-cross-linked pDNA-contained polyplexes. The obtained mannose modified polyplexes exhibit ca. 500-times greater transfection activity in IC-21 macrophages compared to the mannose-free polyplexes. This result greatly exceeds the targeting gene transfer effects previously described using mannose receptor targeted non-viral gene delivery systems. These results suggest that Man-PEG-b-pAsp(DET)/pDNA polyplex is a potential vector for immune cells-based gene therapy.

Functional Integrin Regulation Through Interactions with Tetraspanin CD9

Integrins are adhesion receptors that mediate many intercellular and cell-extracellular matrix interactions with relevance in physiology and pathology. Unlike other cellular receptors, integrins critically require activation for ligand binding. Through interaction in cis with other molecules and the formation of tetraspanin-enriched membrane microdomains (TEMs), the tetraspanin CD9 regulates integrin activity and avidity. Here we present three techniques used to study CD9-integrin interactions and integrin activation.

RGDS-Modified Superporous Poly(2-Hydroxyethyl Methacrylate)-Based Scaffolds as 3D In Vitro Leukemia Model

Superporous poly(2-hydroxyethyl methacrylate-co-2-aminoethyl methacrylate) (P(HEMA-AEMA)) hydrogel scaffolds are designed for in vitro 3D culturing of leukemic B cells. Hydrogel porosity, which influences cell functions and growth, is introduced by adding ammonium oxalate needle-like crystals in the polymerization mixture. To improve cell vitality, cell-adhesive Arg-Gly-Asp-Ser (RGDS) peptide is immobilized on the N-(γ-maleimidobutyryloxy)succinimide-activated P(HEMA-AEMA) hydrogels via reaction of SH with maleimide groups. This modification is especially suitable for the survival of primary chronic lymphocytic leukemia cells (B-CLLs) in 3D cell culture. No other tested stimuli (interleukin-4, CD40 ligand, or shaking) can further improve B-CLL survival or metabolic activity. Both unmodified and RGDS-modified P(HEMA-AEMA) scaffolds serve as a long-term (70 days) 3D culture platforms for HS-5 and M2-10B4 bone marrow stromal cell lines and MEC-1 and HG-3 B-CLL cell lines, although the adherent cells retain their physiological morphologies, preferably on RGDS-modified hydrogels. Moreover, the porosity of hydrogels allows direct cell lysis, followed by efficient DNA isolation from the 3D-cultured cells. P(HEMA-AEMA)-RGDS thus serves as a suitable 3D in vitro leukemia model that enables molecular and metabolic assays and allows imaging of cell morphology, interactions, and migration by confocal microscopy. Such applications can prospectively assist in testing of drugs to treat this frequently recurring or refractory cancer.

Molecular Mechanisms of Succinimide Formation from Aspartic Acid Residues Catalyzed by Two Water Molecules in the Aqueous Phase

Aspartic acid (Asp) residues are prone to nonenzymatic isomerization via a succinimide (Suc) intermediate. The formation of isomerized Asp residues is considered to be associated with various age-related diseases, such as cataracts and Alzheimer’s disease. In the present paper, we describe the reaction pathway of Suc residue formation from Asp residues catalyzed by two water molecules using the B3LYP/6-31+G(d,p) level of theory. Single-point energies were calculated using the MP2/6-311+G(d,p) level of theory. For these calculations, we used a model compound in which an Asp residue was capped with acetyl and methylamino groups on the N- and C-termini, respectively. In the aqueous phase, Suc residue formation from an Asp residue was roughly divided into three steps, namely, iminolization, cyclization, and dehydration, with the activation energy estimated to be 109 kJ mol⁻¹. Some optimized geometries and reaction modes in the aqueous phase were observed that differed from those in the gas phase.

Cooperative TiO2 photocatalysis with TEMPO and N-hydroxysuccinimide for blue light-driven selective aerobic oxidation of amines

TiO₂ has been the focus of attention in semiconductor photocatalysis for several decades because it can potentially settle the grand energy and environmental issues with earth-abundant elements of Ti and O. However, because of its wide band gap, TiO₂ can only collect UV light, hindering its practical applications under the illumination of sunlight. In view of this, an interesting phenomenon of light-driven adsorption of amines onto TiO₂ to form a visible light-absorbing complex was adapted to assemble smart photocatalysis. The endurance of this complex was eminently refurbished by blue light-driven continuous adsorption of amines. This in turn promoted a vital selective chemical transformation, blue light-driven selective oxidation of amines into imines with atmospheric dioxygen (O₂). More importantly, the inclusion of TEMPO and N-hydroxysuccinimide (NHS) into the smart photocatalytic system could cooperatively expedite the blue light-driven selective aerobic oxidation of amines into imines through dual independent reaction channels, resembling that of enzymatic catalysis. This work underscores the importance of manoeuvring multiple reaction channels by cooperative photocatalysis during selective chemical transformations.

Application of Safirinium N-Hydroxysuccinimide Esters to Derivatization of Peptides for High-Resolution Mass Spectrometry, Tandem Mass Spectrometry, and Fluorescent Labeling of Bacterial Cells

Mass spectrometry methods are commonly used in the identification of peptides and biomarkers. Due to a relatively low abundance of proteins in biological samples, there is a need for the development of novel derivatization methods that would improve MS detection limits. Hence, novel fluorescent N–hydroxysuccinimide esters of dihydro-[1,2,4]triazolo[4,3-a]pyridin-2-ium carboxylates (Safirinium P dyes) have been synthesized. The obtained compounds, which incorporate quaternary ammonium salt moieties, easily react with aliphatic amine groups of peptides, both in solution and on the solid support; thus, they can be applied for derivatization as ionization enhancers. Safirinium tagging experiments with ubiquitin hydrolysate revealed that the sequence coverage level was high (ca. 80%), and intensities of signals were enhanced up to 8-fold, which proves the applicability of the proposed tags in the bottom–up approach. The obtained results confirmed that the novel compounds enable the detection of trace amounts of peptides, and fixed positive charge within the tags results in high ionization efficiency. Moreover, Safirinium NHS esters have been utilized as imaging agents for fluorescent labeling and the microscopic visualization of living cells such as E. coli Top10 bacterial strain.

Improving the Stability of Maleimide-Thiol Conjugation for Drug Targeting

Maleimides are essential compounds for drug conjugation reactions via thiols to antibodies, peptides and other targeting units. However, one main drawback is the occurrence of thiol exchange reactions with, for example, glutathione resulting in loss of the targeting ability. A new strategy to overcome such retro-Michael exchange processes of maleimide-thiol conjugates by stabilization of the thiosuccinimide via a transcyclization reaction is presented. This reaction enables the straightforward synthesis of stable maleimide-thiol adducts essential in drug-conjugation applications.

Oral GLP1 Gene Delivery by an Antibody-Guided Nanomaterial to Treat Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a chronic and progressive hyperglycemic condition. Glucagon-like peptide-1 (GLP1) is an incretin secreted from pancreatic β-cells and helps to produce insulin to balance the blood glucose level without the risk of hypoglycemia. However, the therapeutic application of GLP1 is limited by its intrinsic short half-life and rapid metabolic clearance in the body. To enhance the antidiabetic effect of GLP1, we designed a human cysteine-modified IgG1-Fc antibody-mediated oral gene delivery vehicle, which helps to produce GLP1 sustainably in the target site with the help of increased half-life of the Fc-conjugated nanocarrier, protects GLP1 from acidic and enzymatic degradation in the gastrointestinal (GI) tract, uptakes and transports the GLP1 formulation through the neonatal Fc receptor (FcRn), and helps to release the GLP1 gene in the intestine. Our formulation could reduce the blood glucose from about an average of 320 mg/dL (hyperglycemic) to 150 mg/dL (normal blood glucose concentration) in diabetic mice, which is about 50% reduction of the total blood glucose concentration. GLP1 (500 μg) complexed with the IgG1-Fc carrier was proven to be the optimal dose for a complete reduction of hyperglycemic conditions in diabetic mice. A significant amount of insulin production and the presence of GLP1 peptide were observed in the pancreatic islets of oral GLP1 formulation-treated diabetic mice in immunohistochemistry analysis compared to nontreated diabetic mice. The orally given formulation was completely nontoxic according to the histopathology analysis of mice organ tissues, and no mice death was observed. Our antibody-mediated oral gene delivery system is a promising tool for various oral therapeutic gene delivery applications to treat diseases like diabetes.

Automated Synthesis of Fluorine-18 Labeled CXCR4 Ligand via the Conjugation with Nicotinic Acid N-Hydroxysuccinimide Ester (6-[18F]SFPy)

The C-X-C motif chemokine receptor 4 (CXCR4) is a seven-transmembrane G protein-coupled receptor that is overexpressed in numerous diseases, particularly in various cancers and is a powerful chemokine, attracting cells to the bone marrow niche. Therefore, CXCR4 is an attractive target for imaging and therapeutic purposes. The goal of this study is to develop an efficient, reproducible, and straightforward method to prepare a fluorine-18 labeled CXCR4 ligand. 6-[18F]Fluoronicotinic acid-2,3,5,6-tetrafluorophenyl ester (6-[18F]FPy-TFP) and nicotinic acid N-hydroxysuccinimide ester (6-[18F]SFPy) have been prepared using 'fluorination on the Sep-Pak' method. Conjugation of 6-[18F]SFPy or 6-[18F]FPy-TFP with the alpha-amino group at the N terminus of the protected T140 precursor followed by deprotection, yielded the final product 6-[18F]FPy-T140. The overall radiochemical yields were 6-17% (n = 15, decay-corrected) in a 90-min radiolabeling time with a radiochemical purity >99%. 6-[18F]FPy-T140 exhibited high specific binding and nanomolar affinity for CXCR4 in vitro, indicating that the biological activity of the peptide was preserved. For the first time, [18F]SFPy has been prepared using 'fluorination on the Sep-Pak' method that allows rapid automated synthesis of 6-[18F]FPy-T140. In addition to increased synthetic efficiency, this construct binds with CXCR4 in high affinity and may have potential as an in vivo positron emission tomography (PET) imaging agent. This radiosynthesis method should encourage wider use of this PET agent to quantify CXCR4 in both research and clinical settings.

Light microscopy of proteins in their ultrastructural context

Resolving the distribution of specific proteins at the nanoscale in the ultrastructural context of the cell is a major challenge in fluorescence microscopy. We report the discovery of a new principle for an optical contrast equivalent to electron microscopy (EM) which reveals the ultrastructural context of the cells with a conventional confocal microscope. By decrowding the intracellular space through 13 to 21-fold physical expansion while simultaneously retaining the proteins, bulk (pan) labeling of the proteome resolves local protein densities and reveals the cellular nanoarchitecture by standard light microscopy.

Instant tough bioadhesive with triggerable benign detachment

Bioadhesives such as tissue adhesives, hemostatic agents, and tissue sealants have potential advantages over sutures and staples for wound closure, hemostasis, and integration of implantable devices onto wet tissues. However, existing bioadhesives display several limitations including slow adhesion formation, weak bonding, low biocompatibility, poor mechanical match with tissues, and/or lack of triggerable benign detachment. Here, we report a bioadhesive that can form instant tough adhesion on various wet dynamic tissues and can be benignly detached from the adhered tissues on demand with a biocompatible triggering solution. The adhesion of the bioadhesive relies on the removal of interfacial water from the tissue surface, followed by physical and covalent cross-linking with the tissue surface. The triggerable detachment of the bioadhesive results from the cleavage of bioadhesive's cross-links with the tissue surface by the triggering solution. After it is adhered to wet tissues, the bioadhesive becomes a tough hydrogel with mechanical compliance and stretchability comparable with those of soft tissues. We validate in vivo biocompatibility of the bioadhesive and the triggering solution in a rat model and demonstrate potential applications of the bioadhesive with triggerable benign detachment in ex vivo porcine models.

Kinetic and thermodynamic study of c-Met interaction with single chain fragment variable (scFv) antibodies using phage based surface plasmon resonance

Mesenchymal epithelial transition factor (c-Met) has been recently regarded as an attractive target for the treatment of cancer. Our previous study showed that c-Met-specific single chain fragment variables (scFvs) can be considered as a promising therapy for cancer, however, their molecular interaction with c-Met protein have not been assessed. Accordingly, in the current study we aim to evaluate the kinetic and thermodynamic properties of c-Met interaction with these scFvs as anticancer agents by means of surface plasmon resonance (SPR) technique. Phage-scFvs were immobilized on the 11-mercaptoundecanoic acid gold chips after carboxylic groups activation by N-ethyl-N-(3-diethylaminopropyl) carbodiimide/N-hydroxysuccinimide and, then the c-Met binding to each scFvs (ES1, ES2, and ES3) at different concentrations (ranging from 20 to 665 μM) was explored. Kinetic studies revealed that ES1 has the highest affinity (K_D = 3.36 × 10^-8) toward its target at 25°C. Calculation of thermodynamic parameters also showed positive values for enthalpy and entropy changes, which was representative of hydrophobic forces between c-Met and ES1. Furthermore, the positive value of Gibbs free energy indicated that c-Met binding to ES1 was enthalpy-driven. Taken together, we concluded that produced ES1 can be applied as promising scFv-based therapy for diagnosis or targeting of c-Met in various cancers.

CD24-targeted intraoperative fluorescence image-guided surgery leads to improved cytoreduction of ovarian cancer in a preclinical orthotopic surgical model

BACKGROUND

The completeness of resection is a key prognostic indicator in patients with ovarian cancer, and the application of tumour-targeted fluorescence image-guided surgery (FIGS) has led to improved detection of peritoneal metastases during cytoreductive surgery. CD24 is highly expressed in ovarian cancer and has been shown to be a suitable biomarker for tumour-targeted imaging.

METHODS

CD24 expression was investigated in cell lines and heterogenous patient-derived xenograft (PDX) tumour samples of high-grade serous ovarian carcinoma (HGSOC). After conjugation of the monoclonal antibody CD24 to the NIR dye Alexa Fluor 750 and the evaluation of the optimal pharmacological parameters (OV-90, n = 21), orthotopic HGSOC metastatic xenografts (OV-90, n = 16) underwent cytoreductive surgery with real-time feedback. The impact of intraoperative CD24-targeted fluorescence guidance was compared to white light and palpation alone, and the recurrence of disease was monitored post-operatively (OV-90, n = 12). CD24-AF750 was further evaluated in four clinically annotated orthotopic PDX models of metastatic HGSOC, to validate the translational potential for intraoperative guidance.

FINDINGS

CD24-targeted intraoperative NIR FIGS significantly (47•3%) improved tumour detection and resection, and reduced the post-operative tumour burden compared to standard white-light surgery in orthotopic HGSOC xenografts. CD24-AF750 allowed identification of minuscule tumour lesions which were undetectable with the naked eye in four HGSOC PDX.

INTERPRETATION

CD24-targeted FIGS has translational potential as an aid to improve debulking surgery of ovarian cancer.

FUNDING

This study was supported by the H2020 program MSCA-ITN [675743], Helse Vest RHF, and Helse Bergen HF [911809, 911852, 912171, 240222, 911974, HV1269], as well as by The Norwegian Cancer Society [182735], and The Research Council of Norway through its Centres of excellence funding scheme [223250, 262652].

Chemical Tagging of Membrane Proteins Enables Oriented Binding on Solid Surfaces

In biological systems, membrane proteins play major roles in energy conversion, transport, sensing, and signal transduction. Of special interest are the photosynthetic reaction centers involved in the initial process of light energy conversion to electrical and chemical energies. The oriented binding of membrane proteins to solid surfaces is important for biotechnological applications. In some cases, novel properties are generated as a result of the interaction between proteins and solid surfaces. We developed a novel approach for the oriented tagging of membrane proteins. In this unique process, bifunctional molecules are used to chemically tag the exposed surfaces of membrane proteins at selected sides of membrane vesicles. The isolated tagged membrane proteins were self-assembled on solid surfaces, leading to the fabrication of dens-oriented layers on metal and glass surfaces, as seen from the atomic force microscopy (AFM) images. In this work, we used chromatophores and membrane vesicles containing protein chlorophyll complexes for the isolation of the bacterial reaction center and photosystem I, from photosynthetic bacteria and cyanobacteria, respectively. The oriented layers, which were fabricated on metal surfaces, were functional and generated light-induced photovoltage that was measured by the Kalvin probe apparatus. The polarity of the photovoltage depended on the orientation of proteins in the layers. Other membrane proteins can be tagged by the same method. However, we preferred the use of reaction centers because their orientation can be easily detected by the polarity of their photovoltages.

2'-(1H-phenanthro[9,10-d]imidazol-2-yl)-phenyl-4-carboxylic acid N-hydroxysuccinimide ester: A new phenanthroimidazole derivative as a fluorescent probe for medical imaging applications

In this study a new probe (2'-(1H-phenanthro[9,10-d]imidazol-2-yl)-phenyl-4-carboxylic acid N-hydroxysuccinimide ester, PB1-1) was synthesized and presented, containing the ester group as reactive group for medical imaging applications. The tests included a comparison to the PB1 probe with the aldehyde group described earlier. Also, the photophysics of PB1 and PB1-1 when conjugated to albumin (HSA) and concanavalin A (Con A) was studied. The fluorescence anisotropy measurements and the method of fluorescence quenching of protein were used to examine these interactions. The results showed that both dyes are highly bound to the studied proteins, especially PB1-1. In the present study we also compared the stability of prepared conjugates. The in vitro study have shown that all tested compounds presented to be usable in the case of fixated cell staining. PB1-1-ConA and PB1-1-HSA were characterized with the lowest cytotoxicity during the MTT assay, and thus should be more suitable for live imaging applications than PB1-ConA and PB1-HSA. The results obtained in this work confirmed the theses presented in in silico studies as to the correctness of the choice of ester group as actively binding to the protein. At the same time, we have experimentally demonstrated the significant influence of a probe-protein linker on the spectral properties of conjugates used in medical imaging. We have clearly indicated that a detailed analysis of derivatives with different reactive group allows for proper probe selection. We also pointed out that based on the geometric skeleton of one dye, a whole range of fluorescent probes with different absorption and fluorescence spectra can be obtained for in vitro tests in medical imaging.

An Injectable and Instant Self-Healing Medical Adhesive for Wound Sealing

Designing versatile functional medical adhesives with injectability, self-healing, and strong adhesion is of great significance to achieve desirable therapeutic effects for promoting wound sealing in healthcare. Herein, a self-healing injectable adhesive is fabricated by physical interaction of polyphenol compound tannic acid (TA) and eight-arm poly(ethylene glycol) end-capped with succinimide glutarate active ester (PEG-SG). The hydrogen bonding induced from the structural unit (-CH₂-CH₂-O-) of PEG and catechol hydroxyl (-OH) of TA, accompanied by ester exchange between N-hydroxysuccinimide (-NHS) and amino (-NH₂) of proteins, contributes to self-healing ability and rapid strong adhesion. Notably, the PEG/TA adhesive can repeatedly adhere to rigid porcine tissues, close the coronary artery under a large incision tension, and bear a heavy load of 2 kg. By exhibiting shear-thinning and anti-swelling properties, the PEG/TA adhesive can be easily applied through single-syringe extrusion onto various wounds. The single-channel toothpaste-like feature of the adhesive ensures its storage hermetically for portable usage. Moreover, in vivo operation and histological H&E staining results indicate that the PEG/TA adhesive greatly accelerates wound healing and tissue regeneration in a rat model. With the specialty of injectability, instant self-healing, and long-lasting strong adhesion to facilitate excellent therapeutic effects, the multifunctional PEG/TA adhesive may provide a new alternative for self-rescue and surgical situations.

The Isotope-Labeled, MS-Cleavable Cross-Linker Disuccinimidyl Dibutyric Urea for Improved Cross-Linking/Mass Spectrometry Studies

Previous studies have shown the benefits of the amine-reactive, CID-MS/MS-cleavable cross-linker disuccinimidyl dibutyric urea (DSBU) for structural proteomics studies via cross-linking/MS (XL-MS). To further facilitate the automation of XL-MS experiments, we synthesized a deuterated (D₁₂) version of the DSBU cross-linker combining the advantages of MS-cleavable linkers and isotope labeling. The rationale of conducting XL-MS with a mixture of unlabeled and stable isotope-labeled DSBU is to obtain characteristic mass differences at the MS level indicating cross-linked species. These cross-linked species can then be selected for fragmentation by collisional activation. At the MS/MS level, the characteristic 26-u doublets arising from cleavage of the central urea group in DSBU confirm the amino acid sequences of cross-linked peptides as well as the exact cross-linking sites. D₁₂-labeled DSBU was tested on three systems with increasing complexity: (i) bovine serum albumin as purified protein, (ii) Escherichia coli ribosome as large, multimeric protein assembly, and (iii) Drosophila embryo extract as complete proteome. We demonstrate the benefits arising from the use of isotope-labeled DSBU for an automated assignment of cross-linked products. Combining isotope labeling and MS cleavability in one cross-linker resulted in higher cross-link identification numbers especially for highly complex protein mixtures.

Tracking Pathogen Infections by Time-Resolved Chemical Proteomics

Studying the dynamic interaction between host cells and pathogen is vital but remains technically challenging. We describe herein a time-resolved chemical proteomics strategy enabling host and pathogen temporal interaction profiling (HAPTIP) for tracking the entry of a pathogen into the host cell. A novel multifunctional chemical proteomics probe was introduced to label living bacteria followed by in vivo crosslinking of bacteria proteins to their interacting host-cell proteins at different time points initiated by UV for label-free quantitative proteomics analysis. We observed over 400 specific interacting proteins crosslinked with the probe during the formation of Salmonella-containing vacuole (SCV). This novel chemical proteomics approach provides a temporal interaction profile of host and pathogen in high throughput and would facilitate better understanding of the infection process at the molecular level.

N-Hydroxysuccinimide-Modified Ethynylphosphonamidates Enable the Synthesis of Configurationally Defined Protein Conjugates

Herein, the application of N-hydroxysuccinimide-modified phosphonamidate building blocks for the incorporation of cysteine-selective ethynylphosphonamidates into lysine residues of proteins, followed by thiol addition with small molecules and proteins, is reported. It is demonstrated that the building blocks significantly lower undesired homo-crosslinking side products that can occur with commonly applied succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC) under physiological pH. The previously demonstrated stability of the phosphonamidate moiety additionally solves the problem of premature maleimide hydrolysis, which can hamper the efficiency of subsequent thiol addition. Furthermore, a method to separate the phosphonamidate enantiomers to be able to synthesize protein conjugates in a defined configuration has been developed. Finally, the building blocks are applied to the construction of functional antibody-drug conjugates, analogously to FDA-approved, SMCC-linked Kadcyla, and to the synthesis of a functional antibody-protein conjugate.

Surface Modification with Control over Ligand Density for the Study of Multivalent Biological Systems

In the study of multivalent interactions at interfaces, as occur for example at cell membranes, the density of the ligands or receptors displayed at the interface plays a pivotal role, affecting both the overall binding affinities and the valencies involved in the interactions. In order to control the ligand density at the interface, several approaches have been developed, and they concern the functionalization of a wide range of materials. Here, different methods employed in the modification of surfaces with controlled densities of ligands are being reviewed. Examples of such methods encompass the formation of self-assembled monolayers (SAMs), supported lipid bilayers (SLBs) and polymeric layers on surfaces. Particular emphasis is given to the methods employed in the study of different types of multivalent biological interactions occurring at the functionalized surfaces and their working principles.

Electrochemical Detection of C-Reactive Protein in Human Serum Based on Self-Assembled Monolayer-Modified Interdigitated Wave-Shaped Electrode

An electrochemical capacitance immunosensor based on an interdigitated wave-shaped micro electrode array (IDWµE) for direct and label-free detection of C-reactive protein (CRP) was reported. A self-assembled monolayer (SAM) of dithiobis (succinimidyl propionate) (DTSP) was used to modify the electrode array for antibody immobilization. The SAM functionalized electrode array was characterized morphologically by atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX). The nature of gold-sulfur interactions on SAM-treated electrode array was probed by X-ray photoelectron spectroscopy (XPS). The covalent linking of anti-CRP-antibodies onto the SAM modified electrode array was characterized morphologically through AFM, and electrochemically through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The application of phosphate-buffered saline (PBS) and human serum (HS) samples containing different concentrations of CRP in the electrode array caused changes in the electrode interfacial capacitance upon CRP binding. CRP concentrations in PBS and HS were determined quantitatively by measuring the change in capacitance (ΔC) through EIS. The electrode immobilized with anti-CRP-antibodies showed an increase in ΔC with the addition of CRP concentrations over a range of 0.01-10,000 ng mL-1. The electrode showed detection limits of 0.025 ng mL-1 and 0.23 ng mL-1 (S/N = 3) in PBS and HS, respectively. The biosensor showed a good reproducibility (relative standard deviation (RSD), 1.70%), repeatability (RSD, 1.95%), and adequate selectivity in presence of interferents towards CRP detection. The sensor also exhibited a significant storage stability of 2 weeks at 4 °C in 1× PBS.

Polyamidoamide Dendrimers and Cross-Linking Agents for Stabilized Bioenzymatic Resistant Metal-Free Bovine Collagen

The work reports the use of polyamidoamine dendrimers (PAMAM) and a cross-linking agent, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide/N-hydroxysuccinimide (EDC/NHS) or 4-(4,6-dimethoxy[1,3,5]triazin-2-yl)-4-methyl-morpholinium chloride (DMTMM), for the thermal stabilization of dermal bovine collagen. The efficiency of EDC/NHS/PAMAM and DMTMM/PAMAM in the cross-linking of collagen is correlated to the increase of the collagen shrinkage temperature (Ts), measured by differential scanning calorimetry (DSC). An alternative enzymatic protocol was adopted to measure the degradability of EDC/NHS/PAMAM tanned hides; these data are correlated to the thermal stability values measured by DSC. In the presence of PAMAMs, EDC/NHS provides very high stabilization of bovine dermal collagen, giving Ts of up to 95 °C, while DMTMM achieves lower stabilization. Preliminary tanning tests carried out in best reaction conditions show that EDC/NHS/PAMAM could be an interesting, environmentally-sustainable tanning system which is completely free of metals, formaldehyde, and phenols. Two new unreported dendrimeric species were synthesized and employed.

Characterization by Empirical and Computational Methods of Dictyospiromide, an Intriguing Antioxidant Alkaloid from the Marine Alga Dictyota coriacea

The challenging structural motif of dictyospiromide (1), a spirosuccinimide alkaloid with antioxidant properties that are associated with activation of the Nrf2/ARE signaling pathway, was assigned using contemporary NMR experiments complemented with anisotropic NMR, chiroptical, and computational methodologies. Anisotropic NMR parameters provided critical orthogonal verification of the configuration of the difficult to assign spiro carbon and the other stereogenic centers in 1.

Tandem Mass Tag Labeling Facilitates Reversed-Phase Liquid Chromatography-Mass Spectrometry Analysis of Hydrophilic Phosphopeptides

Protein phosphorylation is a critical post-translational modification (PTM). Despite recent technological advances in reversed-phase liquid chromatography (RPLC)-mass spectrometry (MS)-based proteomics, comprehensive phosphoproteomic coverage in complex biological systems remains challenging, especially for hydrophilic phosphopeptides with enriched regions of serines, threonines, and tyrosines that often orchestrate critical biological functions. To address this issue, we developed a simple, easily implemented method to introduce a commonly used tandem mass tag (TMT) to increase peptide hydrophobicity, effectively enhancing RPLC-MS analysis of hydrophilic peptides. Different from conventional TMT labeling, this method capitalizes on using a nonprimary amine buffer and TMT labeling occurring before C18-based solid phase extraction. Through phosphoproteomic analyses of MCF7 cells, we have demonstrated that this method can greatly increase the number of identified hydrophilic phosphopeptides and improve MS detection signals. We applied this method to study the peptide QPSSSR, a very hydrophilic tryptic peptide located on the C-terminus of the G protein-coupled receptor (GPCR) CXCR3. Identification of QPSSSR has never been reported, and we were unable to detect it by traditional methods. We validated our TMT labeling strategy by comparative RPLC-MS analyses of both a hydrophilic QPSSSR peptide library as well as common phosphopeptides. We further confirmed the utility of this method by quantifying QPSSSR phosphorylation abundances in HEK 293 cells under different treatment conditions predicted to alter QPSSSR phosphorylation. We anticipate that this simple TMT labeling method can be broadly used not only for decoding GPCR phosphoproteome but also for effective RPLC-MS analysis of other highly hydrophilic analytes.

Self-assembly of collagen bundles and enhanced piezoelectricity induced by chemical crosslinking

The piezoelectricity of collagen is purported to be linked to many biological processes including bone formation and wound healing. Although the piezoelectricity of tissue-derived collagen has been documented across the length scales, little work has been undertaken to characterise the local electromechanical properties of processed collagen, which is used as a base for tissue-engineering implants. In this work, three chemically distinct treatments used to form structurally and mechanically stable scaffolds-EDC-NHS, genipin and tissue transglutaminase-are investigated for their effect on collagen piezolectricity. Crosslinking with EDC-NHS is noted to produce a distinct self-assembly of the fibres into bundles roughly 300 nm in width regardless of the collagen origin. These fibre bundles also show a localised piezoelectric response, with enhanced vertical piezoelectricity of collagen. Such topographical features are not observed with the other two chemical treatments, although the shear piezoelectric response is significantly enhanced upon crosslinking. These observations are reconciled by a proposed effect of the crosslinking mechanisms on the molecular and nanostructure of collagen. These results highlight the ability to modify the electromechanical properties of collagen using chemical crosslinking methods.

The Role of Orientation of Surface Bound Dihydropyrrol-2-ones (DHP) on Biological Activity

Quorum sensing (QS) signaling system is important for bacterial growth, adhesion, and biofilm formation resulting in numerous infectious diseases. Dihydropyrrol-2-ones (DHPs) represent a novel class of antimicrobial agents that inhibit QS, and are less prone to develop bacterial resistance due to their non-growth inhibition mechanism of action which does not cause survival pressure on bacteria. DHPs can prevent bacterial colonization and quorum sensing when covalently bound to substrates. In this study, the role of orientation of DHP compounds was investigated after covalent attachment by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) coupling reaction to amine-functionalized glass surfaces via various positions of the DHP scaffold. The functionalized glass surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and contact angle measurements and tested for their in vitro biological activity against S. aureus and P. aeruginosa. DHPs attached via the N-1 position resulted in the highest antibacterial activities against S. aureus, while no difference was observed for DHPs attached either via the N-1 position or the C-4 phenyl ring against P. aeruginosa.

Quantitative Photo-crosslinking Mass Spectrometry Revealing Protein Structure Response to Environmental Changes

Protein structures respond to changes in their chemical and physical environment. However, studying such conformational changes is notoriously difficult, as many structural biology techniques are also affected by these parameters. Here, the use of photo-crosslinking, coupled with quantitative crosslinking mass spectrometry (QCLMS), offers an opportunity, since the reactivity of photo-crosslinkers is unaffected by changes in environmental parameters. In this study, we introduce a workflow combining photo-crosslinking using sulfosuccinimidyl 4,4'-azipentanoate (sulfo-SDA) with our recently developed data-independent acquisition (DIA)-QCLMS. This novel photo-DIA-QCLMS approach is then used to quantify pH-dependent conformational changes in human serum albumin (HSA) and cytochrome C by monitoring crosslink abundances as a function of pH. Both proteins show pH-dependent conformational changes resulting in acidic and alkaline transitions. 93% and 95% of unique residue pairs (URP) were quantifiable across triplicates for HSA and cytochrome C, respectively. Abundance changes of URPs and hence conformational changes of both proteins were visualized using hierarchical clustering. For HSA we distinguished the N-F and the N-B form from the native conformation. In addition, we observed for cytochrome C acidic and basic conformations. In conclusion, our photo-DIA-QCLMS approach distinguished pH-dependent conformers of both proteins.

Reactive Conjugated Polymers for the Modulation of Islet Amyloid Polypeptide Assembly

Misfolding and abnormal assembly of proteins cause many intractable diseases. The modulation of the assembly process of these proteins could contribute to understanding and controlling amyloid protein aggregation. Previous works focused mainly on the inhibition of the assembly process. To broaden the interaction modality of modulators with proteins for developing new modulators, in this work, we designed and synthesized two reactive poly ( p-phenylene vinylene) polymers, respectively, functionalized with N-hydroxysuccinimide ester (PPV-NHS) and pentafluorophenol ester (PPV-PFP), which exhibited the prevention or co-assembly effect on the aggregation process of islet amyloid polypeptide (IAPP). Cell assays demonstrated that both of the two polymers could effectively eliminate the cytotoxicity of IAPP. Moreover, PPV-NHS also could irreversibly disrupt preformed IAPP fibrils. We envision that PPV-NHS and PPV-PFP might offer a new design method for the modulation of protein assembly.

Carbodiimide Conjugation of Latent Transforming Growth Factor β1 to Superparamagnetic Iron Oxide Nanoparticles for Remote Activation

Conjugation of latent growth factors to superparamagnetic iron oxide nanoparticles (SPIONs) is potentially useful for magnetically triggered release of bioactive macromolecules. Thus, the goal of this work was to trigger the release of active Transforming Growth-Factor Beta (TGF-β) via magnetic hyperthermia by binding SPIONs to the latent form of TGF-β, since heat has been shown to induce release of TGF-β from the latent complex. Commercially available SPIONS with high specific absorption rates (SAR) were hydrolyzed in 70% ethanol to create surface carboxylic acid conjugation sites for carbodiimide chemistry. Fourier-Transform Infra-Red (FTIR) analysis verified the conversion of maleic anhydride to maleic acid. 1-Ethyl-2-(3-dimethyulaminopropyl) carbodiimide (EDC) and N-hydroxysulfosuccinimide (Sulfo-NHS) were used to bind to the open conjugation sites of the SPION in order to graft latent TGF-β onto the particles. The resulting conjugated particles were imaged with transmission electron microscopy (TEM), and the complexed particles were characterized by dynamic light scattering (DLS) and superconducting quantum interference device (SQUID) magnetometry. Enzyme-linked immunosorbent assay (ELISA) was used to assess the thermally triggered release of active TGF-β from the latent complex, demonstrating that conjugation did not interfere with release. Results showed that latent TGF-β was successfully conjugated to the iron oxide nanoparticles, and magnetically triggered release of active TGF-β was achieved.

Antibody conjugation to carboxyl-modified microspheres through N-hydroxysuccinimide chemistry for automated immunoassay applications: A general procedure

Immunochemical techniques are the workhorse for sample enrichment and detection of a large variety of analytes. In contrast to classical microtiter plate-based assays, microparticles are a next generation solid support, as they promote automation of immunoassays using flow-based techniques. Antibody immobilization is a crucial step, as these reagents are expensive, and inefficient coupling can result in low sensitivities. This paper proposes a general procedure for efficient immobilization of antibodies onto TentaGel particles, via N-hydroxysuccinimide chemistry. The goal was the preparation of solid supports with optimum immunorecognition, while increasing the sustainability of the process. The influence of buffer composition, activation and coupling time, as well as the amount of antibody on the immobilization efficiency was investigated, resorting to fluorophore-labeled proteins and fluorescence imaging. Buffer pH and activation time are the most important parameters for efficient coupling. It is demonstrated, that the hydrolysis of N-hydroxysuccinimide esters occurs at similar rates as in solution, limiting the utilizable time for coupling. Finally, applicability of the generated material for automated affinity extraction is demonstrated on the mesofluidic platform lab-on-valve.

Dual-responsive, Methotrexate-loaded, Ascorbic acid-derived Micelles Exert Anti-tumor and Anti-metastatic Effects by Inhibiting NF-κB Signaling in an Orthotopic Mouse Model of Human Choriocarcinoma

Gestational trophoblastic neoplasia (GTN), the most aggressive form of which is choriocarcinoma, can result from over-proliferation of trophoblasts. Treating choriocarcinoma requires high doses of systemic chemotherapeutic agents, which result in nonspecific drug distribution and severe toxicity. To overcome these disadvantages and enhance chemotherapeutic efficacy, we synthesized redox- and pH-sensitive, self-assembling, ascorbic acid-derived (PEG-ss-aAPP) micelles to deliver the drug methotrexate (MTX). Methods: We developed and tested self-assembling PEG-ss-aAPP micelles, which release their drug cargo in response to an intracellular reducing environment and the acidity of the early lysosome or tumoral microenvironment. Uptake into JEG3 choriocarcinoma cancer cells was examined using confocal microscopy and transmission electron microscopy. We examined the ability of MTX-loaded PEG-ss-aAPP micelles to inhibit metastasis in an orthotopic mouse model of human choriocarcinoma. Results: Drug-loaded micelles had encapsulation efficiency above 95%. Particles were spherical based on transmission electron microscopy, with diameters of approximately 229.0 nm based on dynamic light scattering. The drug carrier responded sensitively to redox and pH changes, releasing its cargo in specific environments. PEG-ss-aAPP/MTX micelles efficiently escaped from lysosome/endosomes, and they were effective at producing reactive oxygen species, strongly inducing apoptosis and inhibiting invasion and migration. These effects correlated with the ability of PEG-ss-aAPP/MTX micelles to protect IκBα from degradation, which in turn inhibited translocation of NF-κB p65 to the nucleus. In an orthotopic mouse model of human choriocarcinoma, PEG-ss-aAPP/MTX micelles strongly inhibited primary tumor growth and significantly suppressed metastasis without obvious side effects. Conclusions: Our results highlight the potential of PEG-ss-aAPP micelles for targeted delivery of chemotherapeutic agents against choriocarcinoma.

Computational Studies on Water-Catalyzed Mechanisms for Stereoinversion of Glutarimide Intermediates Formed from Glutamic Acid Residues in Aqueous Phase

Aspartic acid (Asp) residues are prone to non-enzymatic stereoinversion, and Asp-residue stereoinversion is believed to be mediated via a succinimide (SI) intermediate. The stereoinverted Asp residues are believed to cause several age-related diseases. However, in peptides and proteins, few studies have reported the stereoinversion of glutamic acid (Glu) residues whose structures are similar to that of Asp. We previously presumed that Glu-residue stereoinversion proceeds via a glutarimide (GI) intermediate and showed that the calculated activation barriers of SI- and GI-intermediate stereoinversion are almost equivalent in the gas phase. In this study, we investigated the stereoinversion pathways of the l-GI intermediate in the aqueous phase using B3LYP density functional methods. The calculated activation barrier of l-GI-intermediate stereoinversion in the aqueous phase was approximately 36 kcal·mol-1, which was much higher than that in the gas phase. Additionally, as this activation barrier exceeded that of Asp-residue stereoinversion, it is presumed that Glu-residue stereoinversion has a lower probability of proceeding under physiological conditions than Asp-residue stereoinversion.

Labeling Antibodies Using N-Hydroxysuccinimide (NHS)-Fluorescein

N-Hydroxysuccinimide (NHS)-ester derivatives are among the most commonly used reagents for labeling proteins. The method described here can be adapted to use practically any NHS fluorophore. Generally, a fluorophore is covalently bound to a macromolecule such as an antibody and acts as a reporter molecule used to measure the presence of the macromolecule. These fluorescently labeled bioactive reagents are suitable for use in immunofluorescence, flow cytometry, and numerous other biological applications. There are several widely used dyes available in convenient formats. This protocol can be used with any amine-reactive (e.g., PFP, isothiocyanate) fluorophore derivative.

Preparation and in vitro characterization of cross-linked collagen-gelatin hydrogel using EDC/NHS for corneal tissue engineering applications

Corneal disease is considered as the second leading cause of vision loss and keratoplasty is known as an effective treatment for it. However, the tissue engineered corneal substitutes are promising tools in experimental in vivo repair of cornea. Selecting appropriate cell sources and scaffolds are two important concerns in corneal tissue engineering. The object of this study was to investigate biocompatibility and physical properties of the bio-engineered cornea, fabricated from type-I collagen (COL) and gelatin (Gel). Two gelatin based hydrogels cross-linked with EDC/NHS were fabricated, and their physicochemical properties such as equilibrium water content, enzymatic degradation, mechanical properties, rheological, contact angle and optical properties as well as their ability to support human bone-marrow mesenchymal stem cells (hBM-MSCs) survival were characterized. The equilibrium water content and enzymatic degradation of these hydrogels can be easily controlled by adding COL. Our findings suggest that incorporation of COL-I increases optical properties, hydrophilicity, stiffness and Young's modulus. The viability of hBM-MSCs cultured in Gel and Gel: COL was assessed via CCK-8 assay. Also, the morphology of the hBM-MSCs on the top of Gel and Gel: COL hydrogels were characterized by phase-contrast microscopy. This biocompatible hydrogel may promise to be used as artificial corneal substitutes.

Doxorubicin-loaded protease-activated near-infrared fluorescent polymeric nanoparticles for imaging and therapy of cancer

INTRODUCTION

Despite significant progress in the field of oncology, cancer remains one of the leading causes of death. Chemotherapy is one of the most common treatment options for cancer patients but is well known to result in off-target toxicity. Theranostic nanomedicines that integrate diagnostic and therapeutic functions within an all-in-one platform can increase tumor selectivity for more effective chemotherapy and aid in diagnosis and monitoring of therapeutic responses.

MATERIAL AND METHODS

In this work, theranostic nanoparticles were synthesized with commonly used biocompatible and biodegradable polymers and used as cancer contrast and therapeutic agents for optical imaging and treatment of breast cancer. These core-shell nanoparticles were prepared by nanoprecipitation of blends of the biodegradable and biocompatible amphiphilic copolymers poly(lactic-co-glycolic acid)-b-poly-l-lysine and poly(lactic acid)-b-poly(ethylene glycol). Poly-l-lysine in the first copolymer was covalently decorated with near-infrared fluorescent Alexa Fluor 750 molecules.

RESULTS

The spherical nanoparticles had an average size of 60-80 nm. The chemotherapeutic drug doxorubicin was encapsulated in the core of nanoparticles at a loading of 3% (w:w) and controllably released over a period of 30 days. A 33-fold increase in near-infrared fluorescence, mediated by protease-mediated cleavage of the Alexa Fluor 750-labeled poly-l-lysine on the surface of the nanoparticles, was observed upon interaction with the model protease trypsin. The cytocompatibility of drug-free nanoparticles and growth inhibition of drug-loaded nanoparticles on MDA-MB-231 breast cancer cells were investigated with a luminescence cell-viability assay. Drug-free nanoparticles were found to cause minimal toxicity, even at high concentrations (0.2-2,000 µg/mL), while doxorubicin-loaded nanoparticles significantly reduced cell viability at drug concentrations >10 µM. Finally, the interaction of the nanoparticles with breast cancer cells was studied utilizing fluorescence microscopy, demonstrating the potential of the nanoparticles to act as near-infrared fluorescence optical imaging agents and drug-delivery carriers.

CONCLUSION

Doxorubicin-loaded, enzymatically activatable nanoparticles of less than 100 nm were prepared successfully by nanoprecipitation of copolymer blends. These nanoparticles were found to be suitable as controlled drug delivery systems and contrast agents for imaging of cancer cells.

Assay for galactose-deficient IgA1 enables mechanistic studies with primary cells from IgA nephropathy patients

AIMS

IgA nephropathy, the most common primary glomerulonephritis worldwide, is characterized by glomerular deposition of galactose-deficient IgA1 and elevated serum levels of this IgA1 glycoform. Current ELISA methods lack sensitivity to assess galactose deficiency using small amounts of IgA1, which limits studies in primary cells due to modest IgA1 production in isolated peripheral-blood lymphocytes.

METHODS

Lectin from Helix pomatia was conjugated to biotin or acridinium ester and used in ELISA to detect galactose deficiency of IgA1 using small amounts of IgA1.

RESULTS

Lectin conjugated to acridinium had an approximately a log-fold increased sensitivity compared with biotin-labeled lectin.

CONCLUSIONS

The new method of using lectin from Helix pomatia conjugated to acridinium increased assay sensitivity, allowing future mechanistic studies with cultured primary cells.

Quantitative synthesis of protein-DNA conjugates with 1 : 1 stoichiometry

We describe here a binding-facilitated reaction strategy, enabling quantitative conjugation of DNA to native proteins with a desirable 1 : 1 stoichiometry. The technique takes advantage of the iterative affinity interaction and covalent binding processes to achieve complete conjugation. The complete conjugation obviates the need for separation of the protein-DNA conjugates as required by other DNA-protein conjugation methods.

Preparation and characterization of functionalized heparin-loaded poly-Ɛ-caprolactone fibrous mats to prevent infection with human papillomaviruses

In this study, heparin-loaded poly-ɛ-caprolactone (PCL) fibrous mats were prepared and characterized based on their physical, cytotoxic, thermal, and biological properties. The main objective of the work described here was to test the hypothesis that incorporation of heparin into a PCL carrier could serve as bio-compatible material capable of inhibiting Human Papillomavirus (HPV) infection. The idea of firmly anchoring heparin to capture soluble virus, vs. a slow heparin release to inhibit a virus in solution was tested. Thus, one material was produced via conventional heparin matrix encapsulation and electrohydrodynamic fiber processing in one step. A second type of material was obtained via heparin crosslinking. This was achieved by running a carbodiimide/N-hydroxysuccinimide (EDC/NHS) coupling reaction on preformed PCL fibers. In vitro HPV16 L1 protein binding capacity studies were performed. Infectivity assays were done using HPV16 pseudoviruses (PsVs) carrying a GFP plasmid to directly test the ability of the fibrous mats to prevent internalization of HPV PsVs. The crosslinked heparin material presented a dissociation constant (K_d) value comparable to those found in the literature for different heparin-protein L1 peptide interactions. Both materials significantly reduced internalization of HPV PsVs, with a reduction of 94% of PsVs internalization when matrix encapsulated heparin-loaded material was present. Differences in performance between the two proposed structures are discussed.

Expanding the Scope of Cross-Link Identifications by Incorporating Collisional Activated Dissociation and Ultraviolet Photodissociation Methods

With the advent of new cross-linking chemistries, analytical technologies, and search algorithms, cross-linking has become an increasingly popular strategy for evaluating tertiary and quaternary structures of proteins. Collisional activated dissociation remains the primary MS/MS method for identifications of peptide cross-links in high throughput workflows. Ultraviolet photodissociation (UVPD) at 193 nm has emerged as an alternative ion activation method well-suited for characterization of peptides and has been found in some cases to identify different peptides or provide distinctive sequence information than obtained by collisional activation methods. Complementary high energy collision dissociation (HCD) and UVPD were used in the present study to characterize protein cross-linking for bovine serum albumin, hemoglobin, and E. coli ribosome. Cross-links identified by HCD and UVPD using bis(sulfosuccinimidyl)suberate (BS3), a homobifunctional amine-to-amine cross-linker, and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM), a heterofunctional amine-to-carboxylic acid cross-linker, were evaluated in the present study. While more unique BS3 cross-links were identified by HCD, UVPD, and HCD provided a complementary panel of DMTMM cross-links which extended the degree of structural insight obtained for the proteins.