Passive adsorption of immunologically active and inactive synthetic peptides to polystyrene is influenced by the proportion of non-polar residues in the peptide

Sticky Situation: An Investigation of Robust Aqueous-Based Recombinant Spider Silk Protein Coatings and Adhesives

The mechanical properties and biocompatibility of spider silks have made them one of the most sought after and studied natural biomaterials. A biomimetic process has been developed that uses water to solvate purified recombinant spider silk proteins (rSSps) prior to material formation. The absence of harsh organic solvents increases cost effectiveness, safety, and decreases the environmental impact of these materials. This development allows for the investigation of aqueous-based rSSps as coatings and adhesives and their potential applications. In these studies it was determined that fiber-based rSSps in nonfiber formations have the capability to coat and adhere numerous substrates, whether rough, smooth, hydrophobic, or hydrophilic. Further, these materials can be functionalized for a variety of processes. Drug-eluting coatings have been made with the capacity to release a variety of compounds in addition to their inherent ability to prevent blood clotting and biofouling. Additionally, spider silk protein adhesives are strong enough to outperform some conventional glues and still display favorable tissue implantation properties. The physical properties, corresponding capabilities, and potential applications of these nonfibrous materials were characterized in this study. Mechanical properties, ease of manufacturing, biodegradability, biocompatibility, and functionality are the hallmarks of these revolutionary spider silk protein materials.

Plant-Derived Chimeric Virus Particles for the Diagnosis of Primary Sjögren Syndrome

Plants are ideal for the production of protein-based nanomaterials because they synthesize and assemble complex multimeric proteins that cannot be expressed efficiently using other platforms. Plant viruses can be thought of as self-replicating proteinaceous nanomaterials generally stable and easily produced in high titers. We used Potato virus X (PVX), chimeric virus particles, and Cowpea mosaic virus, empty virus-like particles to display a linear peptide (lipo) derived from human lipocalin, which is immunodominant in Sjögren's syndrome (SjS) and is thus recognized by autoantibodies in SjS patient serum. These virus-derived nanoparticles were thus used to develop a diagnostic assay for SjS based on a direct enzyme linked immunosorbent assay format. We found that PVX-lipo formulations were more sensitive than the chemically synthesized immunodominant peptide and equally specific when used to distinguish between healthy individuals and SjS patients. Our novel assay therefore allows the diagnosis of SjS using a simple, low-invasive serum test, contrasting with the invasive labial biopsy required for current tests. Our results demonstrate that nanomaterials based on plant viruses can be used as diagnostic reagents for SjS, and could also be developed for the diagnosis of other diseases.

Increased affinity and solubility of peptides used for direct peptide ELISA on polystyrene surfaces through fusion with a polystyrene-binding peptide tag

Peptide reagents can serve as alternatives or replacements to antibodies in sensing or diagnostic applications. The passive adsorption of peptides onto polystyrene surfaces can limit the target binding capability, especially for short, positively charged, or hydrophobic sequences. In this report, we show that fusing a peptide with a previously characterized 12-amino acid polystyrene binding sequence (PS-tag) improves overall peptide solubility and enzyme-linked immunosorbent assay (ELISA) results using the peptide as a capture agent. Specific improvements for protective antigen (PA; Bacillus anthracis) protein binding peptides selected from bacterial surface display were compared with native or biotinylated peptides. The PS-tag was added to either peptide terminus, using a (Gly)(4) spacer, and comparable binding affinities were obtained. Fusion with the PS-tag did not have any negative impact on peptide secondary structure as measured by circular dichroism. The addition of the PS-tag provides a convenient method to utilize peptide reagents from peptide display libraries as capture agents in an ELISA format without the need for a biotin tag or concerns about passive adsorption of critical residues for target capture.

The experimental design as practical approach to develop and optimize a formulation of peptide-loaded liposomes

To investigate the encapsulation of Print 3G, a peptidic agent that could reduce the angiogenic development of breast tumors, pegylated liposomes used as intravenous vectors were studied and characterized. Recently, the path of liposomes has been explored with success to improve the pharmacological properties of peptidic drugs and to stabilize them. In this study, loaded unilamellar vesicles composed of SPC:CHOL:mPEG2000-DSPE (47:47:6) were prepared by the hydration of lipid film technique. An HPLC method was developed and validated for the determination of Print 3G to calculate its encapsulation efficiency. Observed Print 3G adsorption on different materials employed during liposome preparation (such as glass beads, tubing, and connections for extrusion) led to the modification of the manufacturing method. The freeze-thawing technique was used to enhance the amount of Print 3G encapsulated into blank liposomes prepared using the hydration of lipid film procedure. Many factors may influence peptide entrapment, namely the number of freeze-thawing cycles, the lipid concentration, the peptide concentration, and the mixing time. Consequently, a design of experiments was performed to obtain the best encapsulation efficiency while minimizing the number of experiments. The lipid concentration and the number of freeze-thawing cycles were identified as the positive factors influencing the encapsulation. As a result of the optimization, an optimum was found and encapsulation efficiencies were improved from around 30% to 63%. Liposome integrity was evaluated by photon correlation spectroscopy and freeze-fracture electron microscopy to ensure that the selected formulation possesses the required properties to be a potential candidate for further in vitro and in vivo experiments.

Transport of Insulin in Modified Valia-Chien Chambers and Caco-2 Cell Monolayers

The transport characteristics of insulin were investigated using two different absorption models. Using the modified Valia-Chien chambers, permeability coefficients of insulin in the duodenum, jejunum, and ileum were 0.71x10(-7), 7.11x10(-7) and 9.45x10(-7) cm/s, respectively. In the Caco-2 cell monolayers, the bidirectional transepithelial fluxes of insulin across Caco-2 cell line showed symmetry. Confocal laser scanning microscopy visualized that FD-4 and FITC-insulin were mainly located in the paracellular route. It is evident that the lower intestine might be an advantageous region, and absorption enhancer that helps open tight junctions between cells should be used for oral delivery of insulin.

In situ deprotection: a method for covalent immobilization of peptides with well-defined orientation for use in solid phase immunoassays such as enzyme-linked immunosorbent assay

The orientation of an immobilized antigen is important for recognition by, e.g., an antibody. When noncovalent passive adsorption is used for immobilization, the number of ways that the antigen can attach to the surface is numerous and control of how the antigen orientates on the surface is limited. Covalent immobilization restricts the number of the ways that the antigen can be immobilized to the number of reactive groups on the antigen and, hence, the orientation of the immobilized antigen is more predictable. Peptide antigens were synthesized and purified with protection groups on the lysine and cysteine side chains. These peptides, which have only one good nucleophilic group (the N-terminal alpha-amino group), were immobilized covalently in microtiter plates supplied with tresyl groups on the surface and the protection groups were cleaved off in situ after immobilization. The controlled orientation of these peptides resulted in enhanced recognition by antibodies in general. An enzyme-linked immunosorbent assay for detection of antibodies against a peptide derived from outer surface protein C from Borrelia burgdorferi, found in Lyme borreliosis patients, was established using this strategy. Lyme borreliosis suspect patient sera showed up to a 10-fold increase in the signal when the orientation of the peptide antigen was controlled by the in situ deprotection strategy.

Direct coating of poly(lys) or acetyl-thio-acetyl peptides to polystyrene: the effects in an enzyme-linked immunosorbent assay

Direct adsorption of small peptides to polystyrene surfaces is often not satisfactory. Therefore, a simple and general coating procedure to improve the coating efficiency of small synthetic peptide antigens to polystyrene is described. In this study, the binding capacities of four small synthetic peptides N-terminally linked to various moieties during synthesis were compared to their parent counterparts in terms of the amount of peptide coat concentration required to achieve 50% of the maximum enzyme-linked immunosorbent assay signal. Elongation of a short epitope sequence by an N-terminal acetyl-thio-acetyl (Ata) group or a lysyl moiety resulted in an enormous reduction in peptide coat concentration for all tested peptides of net two to four orders of magnitude when corrected for chain elongation. The optimal length of the lysyl moiety depended on the length of the model peptide. Replacement of both extensions by analogues (i.e., Ata analogues and other basic amino acid residues in the case of the lysyl moiety) was possible without reducing their enhancing properties to a great extent. Additional experiments showed that a lysyl moiety consisting of a linear stretch of seven lysyl moiety consisting of a linear stretch of seven lysyl residues was more effective in comparison to a branched lysyl construct and could easily compete with the multiple antigen peptide approach.