Chitosan and Thiolated Chitosan

Current Methods for Extraction and Concentration of Foodborne Bacteria with Glycan-Coated Magnetic Nanoparticles: A Review

Rapid and accurate food pathogen detection is an essential step to preventing foodborne illnesses. Before detection, removal of bacteria from the food matrix and concentration to detectable levels are often essential steps. Although many reviews discuss rapid concentration methods for foodborne pathogens, the use of glycan-coated magnetic nanoparticles (MNPs) is often omitted. This review seeks to analyze the potential of this technique as a rapid and cost-effective solution for concentration of bacteria directly from foods. The primary focus is the mechanism of glycan-coated MNP binding, as well as its current applications in concentration of foodborne pathogens. First, a background on the synthesis, properties, and applications of MNPs is provided. Second, synthesis of glycan-coated particles and their theorized mechanism for bacterial adhesion is described. Existing research into extraction of bacteria directly from food matrices is also analyzed. Finally, glycan-coated MNPs are compared to the magnetic separation technique of immunomagnetic separation (IMS) in terms of cost, time, and other factors. At its current state, glycan-coated MNPs require more research to fully identify the mechanism, potential for optimization, and extraction capabilities directly in food matrices. However, current research indicates glycan-coated MNPs are an incredibly cost-effective method for rapid food pathogen extraction and concentration.

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.

Ecofriendly multifunctional thiolated carboxymethyl chitosan-based 3D scaffolds with luminescent properties for skin repair and theragnostic of tissue regeneration

Luminescent biopolymers, namely carboxymethyl chitosan, have become a target of attention due to their potential for biomedical applications. In this context, biomaterials capable of improving theragnostic tissue regeneration and provide a tissue repair remain a challenge. This study introduces a new 3D scaffold based on two innovative thiolated carboxymethyl chitosan with cysteine (CMCCys) and 11-mercaptoundecanoic acid (CMCMerc) resulting in enhanced fluorescence of CMC for repair and theragnostic of tissue regeneration. Those thiolated CMCs were intensively characterized by spectroscopy techniques (FTIR, NMR), swelling degree, chemical stability (Gel-fraction, GF) and morphological analysis (SEM, microtomography, BET). In addition, the photoluminescence properties were evaluated and cytocompatibility was performed via in vitro bioassays. The results demonstrated that those scaffolds presented interconnected 3D porous (porosity > 80%), a great GF, and a high degree of thiolation (2%-11%). Furthermore, the spectroscopy analysis elucidated a significant disulfide bond formation, which guaranteed mechanical stability for applications in tissue engineering (elastic modulus, (22 ± 3) kPa and (35 ± 2) kPa, for CMCCys and CMCMerc, respectively). Additionally, the incorporation of thiol group improved the fluorescence of CMC and they presented cytocompatibility > 90%. Thus, for the first time, a multifunctional 3D CMC thiomer was produced for applications in repair and theragnostic of tissue regeneration.

Investigation of gelling behavior of thiolated chitosan in alkaline condition and its application in stent coating

The gelling behaviors of thiolated chitosan (TCS) in alkaline condition were investigated. Thioglycolic acid was conjugated onto chitosan backbone through amide bond formation. The variations of thiol group content were monitored in presence of H2O2 or different pH values (pH 7.0, 8.0, 9.0) in dialysis mode. Different from the decreasing thiol group content upon time in acidic condition, increasing amount of thiol groups was detected in alkaline pH during 120 min dialysis attributed to alkaline hydrolysis of intra-molecular disulfide bonds. The extent of which was larger at higher pH values. Higher degree of thiolation, thiomer concentration or pH values promoted gelation of TCS. Entanglement and coagulation of chitosan molecule chains and re-arrangement of disulfide bonds acted closely and dynamically in the gelation process. Disulfide bonds, especially inter-molecular type, are formed by synergetic effects of thiol/disulfide interchange and thiol/thiol oxidation reactions. TCS coated vascular stent displayed wave-like microstructure of parallel ridges and grooves, which favored HUVECs adhesion and proliferation. The biocompatibility, peculiar morphology and thiol moieties of TCS as stent coating material appear application potential for vascular stent.

Strategies for improving mucosal drug delivery

Within this review we will provide a comprehensive understanding in order to improve existing strategies and to develop new systems to lower the barrier for improving mucosal drug delivery. Mucosal administration of drugs achieves a therapeutical effect as the permeation of significant amounts of a drug is permitted through the absorption membrane. The absorption membrane relies on the mucosal layer and the epithelial tissue. In order to overcome barriers, drug delivery systems have to exhibit various functions and features, such as mucoadhesive and protective activity, solubility improving, permeation and uptake enhancing, and drug release controlling properties. This review also aims to provide an insight of well-distinguished strategies to date, as well as provide a focus on the enhancement of membrane permeability. Furthermore, since the development and functions of drug delivery systems exert a high influence on the ability of drug permeation through membrane, these considerations will also be discussed in this review.

pH/redox responsive core cross-linked nanoparticles from thiolated carboxymethyl chitosan for in vitro release study of methotrexate

A novel amphiphilic thiolated carboxymethyl chitosan was synthesized. It self-assembled into disulfide bond cross-linked nanoparticles in deionized water. The TEM showed that these nanoparticles had a core-shell structure with an average diameter of 160 nm. Dynamic light scattering showed that the nanoparticles were stable in water solution. The particle size changed with pH values and GSH concentrations, and reached a maximum diameter at pH 7.0 and 20mM GSH respectively, exhibiting an obvious pH/redox responsibility. Methotrexate was encapsulated in nanoparticles reaching encapsulation efficiency as much as 43.4%. Release profiles of methotrexate showed a release rate of 19 wt% in pH 7.4 buffer containing 10 μM GSH, whereas as high as 93 wt% in pH 5.0 buffer containing 20mM GSH, indicating that the nanoparticles may be used for tumor-specific drug release. The anticancer activity test in vitro showed that the inhibition rate of methotrexate-loaded nanoparticles against HeLa cells reached 90%.

Thiopyrazole preactivated chitosan: combining mucoadhesion and drug delivery

The objective of this study was to develop a preactivated chitosan derivative by the introduction of thioglycolic acid followed by 3-methyl-1-phenylpyrazole-5-thiol (MPPT) coupling via disulfide bond formation. The newly synthesized conjugate was characterized in terms of water-absorbing capacity, cohesive properties, mucoadhesion and drug release kinetics. Further in vitro characterization was conducted regarding permeation enhancement of the model compound fluorescein isothiocyanate dextran (FD4) and cytotoxic effects on Caco-2 cells. Based on the attachment of the hydrophobic residue, chitosan-S-S-MPPT test discs showed increased stability of the polymer matrix as well as improved water uptake and liberation of fluorescein isothiocyanate dextran (FD4) compared to chitosan only. The mucoadhesive qualities on porcine intestinal mucosa could be improved 38-fold based on the enhanced bonding between chitosan-S-S-MPPT and mucus through the thiol/disulfide exchange reaction of polymer and mucosal cysteine-rich domains supported by MPPT as the leaving group. This novel biomaterial presents a disulfide conjugation-based delivery system that releases the antibacterial thiopyrazole when the polymer comes into contact with the intestinal mucosa. These properties, together with the safe toxicological profile, make chitosan-S-S-MPPT a valuable carrier for mucoadhesive drug delivery systems and a promising matrix for the development of antimicrobial excipients.