Chemical stabilization of γ-polyglutamate by chitosan and the effect of co-solvents on the stability

Chitosan/poly-γ-glutamic acid crosslinked hydrogels: Characterization and application as bio-glues

Ecofriendly hydrogels were prepared using chitosan (CH, 285 kDa) and two fractions of low molecular weight microbial poly-γ-glutamic acid (γ-PGA) (R1 and R2 of 59 kDa and 20 kDa, respectively). The hydrogels were synthesized through sustainable physical blending, employing three CH/γ-PGA mass ratios (1/9, 2/8, and 3/7), resulting in the formation of physically crosslinked materials. The six resulting CH/R1 and CH/R2 hydrogels were physico-chemically characterized and the ones with the highest yields (CH/R1 and CH/R2 ratio of 3/7), analyzed for rheological and morphological properties, showed to act as bio-glues on wood and aluminum compared to commercial vinyl- (V1) and acetovinyl (V2) glues. Lap shear analyses of CH/R1 and CH/R2 blends exhibited adhesive strength on wood, as well as adhesive/cohesive failure like that of V1 and V2. Conversely, CH/R2 had higher adhesive strength and adhesive/cohesive failure on aluminum, while CH/R1 showed an adhesion strength with adhesive failure on the metal similar to that of V1 and V2. Scanning electron microscopy revealed the formation of strong physical bonds between the hydrogels and both substrates. Beyond their use as bio-adhesives, the unique properties of the resulting crosslinked materials make them potentially suitable for various applications in paint, coatings, heritage preservation, and medical sector.

Space Station-like Composite Nanoparticles for Co-Delivery of Multiple Natural Compounds from Chinese Medicine and Hydrogen in Combating Sensorineural Hearing Loss

Ototoxic drugs such as aminoglycoside antibiotics and cisplatin (CDDP) can cause sensorineural hearing loss (SNHL), which is closely related to oxidative stress and the acidification of the inner ear microenvironment. Effective treatment of SNHL often requires multifaceted approach due to the complex pathology, and drug combination therapy is expected to be at the forefront of modern hearing loss treatment. Here, space-station-like composite nanoparticles (CCC@mPP NPs) with pH/oxidation dual responsiveness and multidrug simultaneous delivery capability were constructed and then loaded with various drugs including panax notoginseng saponins (PNS), tanshinone IIA (TSIIA), and ammonia borane (AB) to provide robust protection against SNHL. Molecular dynamics simulation revealed that carboxymethyl chitosan/calcium carbonate-chitosan (CCC) NPs and monomethoxy poly(ethylene glycol)-PLGA (mPP) NPs can rendezvous and dock primarily by hydrogen bonding, and electrostatic forces may be involved. Moreover, CCC@mPP NPs crossed the round window membrane (RWM) and entered the inner ear through endocytosis and paracellular pathway. The docking state was basically maintained during this process, which created favorable conditions for multidrug delivery. This nanosystem was highly sensitive to pH and reactive oxygen species (ROS) changes, as evidenced by the restricted release of payload at alkaline condition (pH 7.4) without ROS, while significantly promoting the release in acidic condition (pH 5.0 and 6.0) with ROS. TSIIA/PNS/AB-loaded CCC@mPP NPs almost completely preserved the hair cells and remained the hearing threshold shift within normal limits in aminoglycoside- or CDDP-treated guinea pigs. Further experiments demonstrated that the protective mechanisms of TSIIA/PNS/AB-loaded CCC@mPP NPs involved direct and indirect scavenging of excessive ROS, and reduced release of pro-inflammatory cytokines. Both in vitro and in vivo experiments showed the high biocompatibility of the composite NPs, even after long-term administration. Collectively, this work suggests that composite NPs is an ideal multi-drug-delivery vehicle and open new avenues for inner ear disease therapies.

Physicochemical Characterization of Chitosan/Poly-γ-Glutamic Acid Glass-like Materials

This paper sets up a new route for producing non-covalently crosslinked bio-composites by blending poly-γ-glutamic acid (γ-PGA) of microbial origin and chitosan (CH) through poly-electrolyte complexation under specific experimental conditions. CH and two different molecular weight γ-PGA fractions have been blended at different mass ratios (1/9, 2/8 and 3/7) under acidic pH. The developed materials seemed to behave like moldable hydrogels with a soft rubbery consistency. However, after dehydration, they became exceedingly hard, glass-like materials completely insoluble in water and organic solvents. The native biopolymers and their blends underwent comprehensive structural, physicochemical, and thermal analyses. The study confirmed strong physical interactions between polysaccharide and polyamide chains, facilitated by electrostatic attraction and hydrogen bonding. The materials exhibited both crystalline and amorphous structures and demonstrated good thermal stability and degradability. Described as thermoplastic and saloplastic, these bio-composites offer vast opportunities in the realm of polyelectrolyte complexes (PECs). This unique combination of properties allowed the bio-composites to function as glass-like materials, making them highly versatile for potential applications in various fields. They hold potential for use in regenerative medicine, biomedical devices, food packaging, and 3D printing. Their environmentally friendly properties make them attractive candidates for sustainable material development in various industries.

Shifting archetype to nature's hidden gems: from sources, purification to uncover the nutritional potential of bioactive peptides

Contemporary scientific findings revealed that our daily food stuffs are enriched by encrypted bioactive peptides (BPs), evolved by peptide linkage of amino acids or encrypted from the native protein structures. Remarkable to these BPs lies in their potential health benefiting biological activities to serve as nutraceuticals or a lead addition to the development of functional foods. The biological activities of BPs vary depending on the sequence as well as amino acid composition. Existing database records approximately 3000 peptide sequences which possess potential biological activities such as antioxidants, antihypertensive, antithrombotic, anti-adipogenics, anti-microbials, anti-inflammatory, and anti-cancerous. The growing evidences suggest that BPs have very low toxicity, higher accuracy, less tissue accretion, and are easily degraded in the disposed environment. BPs are nowadays evolved as biologically active molecules with potential scope to reduce microbial contamination as well as ward off oxidation of foods, amend diverse range of human diseases to enhance the overall quality of human life. Against the clinical and health perspectives of BPs, this review aimed to elaborate current evolution of nutritional potential of BPs, studies pertaining to overcome limitations with respect to special focus on emerging extraction, protection and delivery tools of BPs. In addition, the nano-delivery mechanism of BP and its clinical significance is detailed. The aim of current review is to augment the research in the field of BPs production, identification, characterisation and to speed up the investigation of the incredible potentials of BPs as potential nutritional and functional food ingredient.

Interaction and phase behavior of whey protein and propylene glycol alginate complex condensates

Whey protein (WP) is ubiquitously applied in food products, but its sensitivity to food processing conditions has limited its application. Herein, we chose propylene glycol alginate (PGA) to combine with WP to enhance its stability. The ideal ratio of WP/PGA for coacervation was 3:1, and the soluble complex and insoluble complex were formed at pH 5.2 (pHc) and pH 4.4 (pHφ1) at this ratio, respectively. The UV absorption spectra, fluorescence spectra, and XRD results revealed that the interaction between PGA and WP changed the tertiary conformation of WP. The FTIR and molecular docking results suggested electrostatic interactions, hydrogen bonding and hydrophobic interactions were all involved in the formation of WP-PGA complexes, and the thermal stability of WP was improved based on the DSC results. These findings supported PGA to keep dairy products stable and transparent at the isoelectric point and WP-PGA complexes could be applied in encapsulating bioactive substances.

Whey Protein Isolate-Chitosan PolyElectrolyte Nanoparticles as a Drug Delivery System

Whey protein isolate (WPI), employed as a carrier for a wide range of bioactive substances, suffers from a lack of colloidal stability in physiological conditions. Herein, we developed innovative stabilized PolyElectrolyte Nanoparticles (PENs) obtained by two techniques: polyelectrolyte complexation of negatively charged WPI and positively charged chitosan (CS), and ionic gelation in the presence of polyanion tripolyphosphate (TPP). Therefore, the WPI-based core was coated with a CS-based shell and then stabilized by TPP at pH 8. The nanostructures were characterized by physiochemical methods, and their encapsulation efficiency and in vitro release were evaluated. The spherical NPs with an average size of 248.57 ± 5.00 nm and surface charge of +10.80 ± 0.43 mV demonstrated high encapsulation efficiency (92.79 ± 0.69) and sustained release of a positively charged chemotherapeutic agent such as doxorubicin (DOX). Z-average size and size distribution also presented negligible increases in size and aggregates during the three weeks. The results obtained confirm the effectiveness of the simultaneous application of these methods to improve the colloidal stability of PEN.

Bottlebrush inspired injectable hydrogel for rapid prevention of postoperative and recurrent adhesion

Postsurgical adhesion is a common clinic disease induced by surgical trauma, accompanying serious subsequent complications. Current non-surgical approaches of drugs treatment and biomaterial barrier administration only show limited prevention effects and couldn't effectively promote peritoneum repair. Herein, inspired by bottlebrush, a novel self-fused, antifouling, and injectable hydrogel is fabricated by the free-radical polymerization in aqueous solution between the methacrylate hyaluronic acid (HA-GMA) and N-(2-hydroxypropyl) methacrylamide (HPMA) monomer without any chemical crosslinkers, termed as H-HPMA hydrogel. The H-HPMA hydrogel can be tuned to perform excellent self-fused properties and suitable abdominal metabolism time. Intriguingly, the introduction of the ultra-hydrophilic HPMA chains to the H-HPMA hydrogel affords an unprecedented antifouling capability. The HPMA chains establish a dense hydrated layer that rapidly prevents the postsurgical adhesions and recurrent adhesions after adhesiolysis in vivo. The H-HPMA hydrogel can repair the peritoneal wound of the rat model within 5 days. Furthermore, an underlying mechanism study reveals that the H-HPMA hydrogel significantly regulated the mesothelial-to-mesenchymal transition (MMT) process dominated by the TGF-β-Smad2/3 signal pathway. Thus, we developed a simple, effective, and available approach to rapidly promote peritoneum regeneration and prevent peritoneal adhesion and adhesion recurrence after adhesiolysis, offering novel design ideas for developing biomaterials to prevent peritoneal adhesion.

Catalyst Replacement Policy on Multienzymatic Systems: Theoretical Study in the One-Pot Sequential Batch Production of Lactofructose Syrup

One-pot systems are an interesting proposal to carry out multi-enzymatic reactions, though this strategy implies establishing an optimal balance between the activity and operability of the involved enzymes. This is crucial for enzymes with marked differences in their operational stability, such as one-pot production of lactofructose syrup from cheese whey permeate, which involves two enzymes—β-galactosidase (β-gal) and glucose isomerase (GI). The aim of this work was to study the behavior of one-pot sequential batch production of lactofructose syrup considering both enzymes immobilized individually, in order to evaluate and design a strategy of replacement of the catalysts according to their stabilities. To this end, the modelling and simulation of the process was carried out, considering simultaneously the kinetics of both reactions and the kinetics of inactivation of both enzymes. For the latter, it was also considered the modulating effect that sugars present in the medium may have on the stability of β-gal, which is the less stable enzyme. At the simulated reaction conditions of 40 °C, pH 7, and 0.46 (IUGI/IUβ-gal), the results showed that considering the stability of β-gal under non-reactive conditions, meaning in absence of the effect of modulation, it is necessary to carry out four replacements of β-gal for each cycle of use of GI. On the other hand, when considering the modulation caused by the sugars on the β-gal stability, the productivity increases up to 23% in the case of the highest modulation factor studied (η = 0.8). This work shows the feasibility of conducting a one-pot operation with immobilized enzymes of quite different operational stability, and that a proper strategy of biocatalyst replacement increases the productivity of the process.

Smart co-delivery of miR-34a and cytotoxic peptides (LTX-315 and melittin) by chitosan based polyelectrolyte nanocarriers for specific cancer cell death induction

A novel polyelectrolyte nanocarrier was synthesized via layer-by-layer self-assembly of polycationic and polyanionic chains. The nanocarrier is composed of polyglutamate grafted chitosan core, dextran sulfate as a complexing agent, and polyethyleneimine shell decorated with folic acid. This polyelectrolyte complex has unique physicochemical properties so that the core is considered as an efficient carrier for LTX-315 and melittin peptides, and the shell is suitable for delivery of miR-34a. The spherical nanocarriers with an average size of 123 ± 5 nm and a zeta potential of -36 ± 1 mV demonstrated controlled-release of gene and peptides ensured a synergistic effect in establishing multiple cell death pathways on chemoresistance human breast adenocarcinoma cell line, MDA-MB-231. In vitro cell viability assays also revealed no cytotoxicity for the nanocarriers, and an IC50 of 15 μg/mL and 150 μg/mL for melittin and LTX-315, respectively, after 48 h, whereas co-delivery of melittin with miR-34a increased smart death induction by 54%.