Synthesis and characterization of a novel chitosan-N-acetyl-homocysteine thiolactone polymer using MES buffer

Robust and bioaffinity-enhanced nanocarrier based immunochromatographic assay with simplified sample preparation for pentachlorophenol sodium in animal tissues

Sample pretreatment is directly related to the accuracy and reproducibility of test results, simple and controllable sample pretreatment can greatly reduce analysis errors. Herein, MIL-88B-NH2 was synthesized with a regular octahedral rigid framework structure and used as antibody carrier to develop an immunochromatographic assay (ICA) for the detection of sodium pentachlorophenol (PCP) in animal tissues. MIL-88B-NH2 has superior molar absorption coefficient, ultrahigh antibody affinity, and extreme detection environmental tolerance, which were 1.57, 2.5, and 2 times higher than those of traditional colloidal gold, respectively. Therefore, even complex animal tissues can be detected by simple extraction without nitrogen blowing. Ultimately, the cut-off values of this method for pork, chicken and shrimp were 8/5/3 μg/kg, the limits of detection were 1.15/1.28/0.25 μg/kg. The recoveries ranged from 95.5% to 103.0%, with the coefficient of variation from 1.87% to 9.69%. A parallel analysis of 30 samples was confirmed by LC-MS/MS; the results showed a good correlation (R2 > 0.95), indicating the authenticity and reliability of the MIL-88B-NH2-ICA. This work provides a detection strategy with enhanced sensitivity and robustness and simplified sample pretreatment, which has broad application prospects.

Derivatization of graphene oxide nanosheets with tunable nitric oxide release for antibacterial biomaterials

Graphene oxide (GO) nanosheets are a promising class of carbon-based materials suitable for application in the construction of medical devices. These materials have inherent antimicrobial properties based on sheet size, but these effects must be carefully traded off to maintain biocompatibility. Chemical modification of functional groups to the lattice structure of GO nanosheets enables unique opportunities to introduce new surface properties to bolster biological effects. Herein, we have developed nitric oxide (NO)-releasing GO nanosheets via immobilization of S-nitrosothiol (RSNO) moieties to GO nanosheets (GO-[NH]x -SNO). These novel RSNO-based GO nanosheets were characterized for chemical functionality via Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and colorimetric assays for functional group quantification. Stoichiometric control of the available RSNO groups functionalized onto the nanosheets was studied using chemiluminescence-based NO detection methods, showing highly tunable NO release kinetics. Studies of electrical stimulation and subsequent electrochemical reduction of the nanosheets demonstrated further tunability of the NO release based on stimuli. Finally, nanosheets were evaluated for cytotoxicity and antibacterial effects, showing strong cytocompatibility with human fibroblasts in parallel to broad antibacterial and anti-biofilm effects against both Gram-positive and Gram-negative strains. In summary, derivatized GO-(NH)x -SNO nanosheets were shown to have tunable NO release properties, enabling application-specific tailoring for diverse biomedical applications such as antimicrobial coatings and composite fillers for stents, sensors, and other medical devices.

Biodegradable Materials for Tissue Engineering: Development, Classification and Current Applications

The goal of this review is to map the current state of biodegradable materials that are used in tissue engineering for a variety of applications. At the beginning, the paper briefly identifies typical clinical indications in orthopedics for the use of biodegradable implants. Subsequently, the most frequent groups of biodegradable materials are identified, classified, and analyzed. To this end, a bibliometric analysis was applied to evaluate the evolution of the scientific literature in selected topics of the subject. The special focus of this study is on polymeric biodegradable materials that have been widely used for tissue engineering and regenerative medicine. Moreover, to outline current research trends and future research directions in this area, selected smart biodegradable materials are characterized, categorized, and discussed. Finally, pertinent conclusions regarding the applicability of biodegradable materials are drawn and recommendations for future research are suggested to drive this line of research forward.

Preparation of chitosan-tannic acid coating and its anti-osteoclast and antibacterial activities in titanium implants

INTRODUCTION

Bacterial infection and aseptic loosening caused by bone resorption at the implant interface are major clinical complications during bone defect implantation surgery, and surface modification of the implant to address the aforementioned problems has long been a research focus.

MATERIALS AND METHODS

In this paper, a chitosan (CTS)-tannic acid (TA) colloid coating with a negative charge and excellent hydrophilicity was prepared on a Ti6Al4V (TC4) surface using a layer-by-layer assembly method. The physical properties, anti-osteoclast activity, and antimicrobial activity of the coatings were investigated.

RESULTS

The findings showed that when the pH value was 5 and the ratio of CTS:TA was 0.8, the carrying rate of TA was the best. Furthermore, the CTS-TA coating had no cytotoxicity on the morphology and proliferation of BMSCs cells and effectively inhibited the differentiation of RAW264.7 cells into osteoclasts and the proliferation of Staphylococcus aureus and Escherichia coli. With the increase in the immersion time of TC4 in CTS-TA colloid solution, the inhibitory effects will also enhance.

CONCLUSION

Therefore, the preparation of the CTS-TA coating provides a revolutionary technique for implant surface modification to avoid postoperative bacterial infection and aseptic loosening.

Thiolactone chemistry, a versatile platform for macromolecular engineering

This review covers the extensive use of γ-thiolactone chemistry as a versatile and powerful tool for macromolecular engineering and the preparation of various polymer architectures, such as functional, alternating, or sequence-controlled (co)polymers.

Headspace study of chiral interconversion of N-acetyl-homocysteine thiolactones

The rate constants for (L)-N-acetyl homocysteine thiolactone enantiomerization have been obtained from batch-wise studies and by dynamic gas chromatography of racemic mixtures. Results from the batch-wise experiments show that the kinetics of racemization at 150 °C is the same for vials made of glass, silanized glass or Teflon-coated glass so that the vial surface exhibited no effect on the kinetics of racemization. From the temperature dependence of the rate constants the preexponential factor, activation energy, the activation Gibbs energy and activation entropy have been obtained from transition state theory. The catalytic effect of G-DP, G-BP and B-DP GC chiral stationary phases on racemization has been observed and quantified by the values of rate constants; B-DP exhibited the greatest activity. The Eyring activation parameters obtained from batch-wise experiment were compared with theoretical values acquired from quantum chemical modelling. Agreement between the experimental and calculated values of activation Gibbs energy, activation enthalpy and activation entropy is good. The dynamic gas chromatography of racemic mixture on chiral B-DP, G-DP and G-BP capillary columns indicate that the rate constants of forward and reverse reactions are different in chiral environments. The greatest accelerating effect in the process of enantiomerization has been identified for G-BP both in the batch-wise experiments and by the dynamic gas chromatography.

Thiolated-Polymer-Based Nanoparticles as an Avant-Garde Approach for Anticancer Therapies-Reviewing Thiomers from Chitosan and Hyaluronic Acid

Thiomers (or thiolated polymers) have broken through as avant-garde approaches in anticancer therapy. Their distinguished reactivity and properties, closely linked to their final applications, justify the extensive research conducted on their preparation and use as smart drug-delivery systems (DDSs). Multiple studies have demonstrated that thiomer-rich nanoformulations can overcome major drawbacks found when administering diverse active pharmaceutical ingredients (APIs), especially in cancer therapy. This work focuses on providing a complete and concise review of the synthetic tools available to thiolate cationic and anionic polymers, in particular chitosan (CTS) and hyaluronic acid (HA), respectively, drawing attention to the most successful procedures. Their chemical reactivity and most relevant properties regarding their use in anticancer formulations are also discussed. In addition, a variety of NP formation procedures are outlined, as well as their use in cancer therapy, particularly for taxanes and siRNA. It is expected that the current work could clarify the main synthetic strategies available, with their scope and drawbacks, as well as provide some insight into thiomer chemistry. Therefore, this review can inspire new research strategies in the development of efficient formulations for the treatment of cancer.

Thiolated Chitosans: A Multi-talented Class of Polymers for Various Applications

Various properties of chitosan can be customized by thiolation for very specific needs in a wide range of application areas. Since the discovery of thiolated chitosans, many studies have proven their advantageous characteristics, such as adhesion to biological surfaces, adjustable cross-linking and swelling behavior, controllable drug release, permeation as well as cellular uptake enhancement, inhibition of efflux pumps and enzymes, complexation of metal ions, antioxidative properties, and radical scavenging activity. Simultaneously, these polymers remain biodegradable without increased toxicity. Within this Review, an overview about the different possibilities to covalently attach sulfhydryl ligands to the polymeric backbone of chitosan is given, and the resulting versatile physiochemical properties are discussed in detail. Furthermore, the broad spectrum of applications for thiolated chitosans in science and industry, ranging from their most advanced use in pharmaceutical and medical science over wastewater treatment to the impregnation of textiles, is addressed.

Nanostructured Chitosan-Based Biomaterials for Sustained and Colon-Specific Resveratrol Release

In the present work, we demonstrate the preparation of chitosan-based composites as vehicles of the natural occurring multi-drug resveratrol (RES). Such systems are endowed with potential therapeutic effects on inflammatory bowel diseases (IBD), such as Crohn's disease (CD) and ulcerative colitis, through the sustained colonic release of RES from long-lasting mucoadhesive drug depots. The loading of RES into nanoparticles (NPs) was optimized regarding two independent variables: RES/polymer ratio, and temperature. Twenty experiments were carried out and a Box⁻Behnken experimental design was used to evaluate the significance of these independent variables related to encapsulation efficiency (EE). The enhanced RES EE values were achieved in 24 h at 39 °C and at RES/polymer ratio of 0.75:1 w/w. Sizes and polydispersities of the optimized NPs were studied by dynamic light scattering (DLS). Chitosan (CTS) dispersions containing the RES-loaded NPs were ionically gelled with tricarballylic acid to yield CTS-NPs composites. Macro- and microscopic features (morphology and porosity studied by SEM and spreadability), thermal stability (studied by TGA), and release kinetics of the RES-loaded CTS-NPs were investigated. Release patterns in simulated colon conditions for 48 h displayed significant differences between the NPs (final cumulative drug release: 79⁻81%), and the CTS-NPs composites (29⁻34%).

Reversible pH-Sensitive Chitosan-Based Hydrogels. Influence of Dispersion Composition on Rheological Properties and Sustained Drug Delivery

The present work deals with the synthesis of micro-structured biomaterials based on chitosan (CTS) for their applications as biocompatible carriers of drugs and bioactive compounds. Twelve dispersions were prepared by means of functional cross-linking with tricarballylic acid (TCA); they were characterized by Fourier transform infrared spectroscopy (FT-IR), modulated temperature differential scanning calorimetry (MTDSC) and scanning electron microscopy (SEM), and their rheological properties were studied. To the best of the authors' knowledge, no study has been carried out on the influence of CTS concentration, degree of cross-linking and drug loading on chitosan hydrogels for drug delivery systems (DDS) and is investigated herein for the first time. The influence of dispersion composition (polymer concentration and degree of cross-linking) revealed to exert a marked impact on its rheological properties, going from liquid-like to viscoelastic gels. The release profiles of a model drug, diclofenac sodium (DCNa), as well as their relationships with polymer concentration, drug loading and degree of cross-linking were evaluated. Similar to the findings on rheological properties, a wide range of release profiles was encountered. These formulations were found to display a well-controlled drug release strongly dependent on the formulation composition. Cumulative drug release under physiological conditions for 96 h ranged from 8% to 67%. For comparative purpose, Voltaren emulgel® from Novartis Pharmaceuticals was also investigated and the latter was the formulation with the highest cumulative drug release (85%). Some formulations showed similar spreadability values to the commercial hydrogel. The comparative study of three batches confirmed the reproducibility of the method, leading to systems particularly suitable for their use as drug carriers.

Ultrasonic synthesis of stable oil filled microcapsules using thiolated chitosan and their characterization by AFM and numerical simulations

An experimental protocol has been developed for synthesizing stable core-shell microcapsules using a biopolymer, chitosan, lacking cross-linkable thiol functional groups. In the first step, thiol moieties were introduced into the backbone of chitosan using dl-N-acetylhomocysteine thiolactone (AHT). In the second step, AHT-modified chitosan shelled microcapsules, encapsulating an oil core, were successfully prepared using high intensity 20 kHz ultrasound. The size of chitosan and AHT modified chitosan microcapsules was found to be in the range of 1-15 μm. The thickness of the microcapsule shell increased with an increase in thiol content. The mechanical properties of microcapsules were evaluated by subjecting the microcapsules to compressive forces by colloidal probe AFM. The stiffness and the Young's modulus of the shell of microcapsules were determined by analyzing the force versus indentation data using Reissner's theory for indentation of thin elastic shells. The stiffness of AHT modified chitosan microcapsules was found to be higher than unmodified chitosan microcapsules. The viability of microcapsules to be embedded into processed food, pharmaceutical and cosmetic products was tested via numerical simulations. The confined capsule in the micro-channel was subjected to linear shear and uniform flows. We used finite element numerical simulations to determine the deformation of microcapsules in flow as a function of shear rate and thickness of the shell. The deformation of capsule was found to be linear with an increase in the shear rate. The deformation decreased with an increase in the thickness of the shell. Based on the simulations, we predict that the microcapsules would survive processing conditions and shear rates used in industrial applications.

Preparation of Chito-Oligomers by Hydrolysis of Chitosan in the Presence of Zeolite as Adsorbent

An increasing interest has recently been shown to use chitin/chitosan oligomers (chito-oligomers) in medicine and food fields because they are not only water-soluble, nontoxic, and biocompatible materials, but they also exhibit numerous biological properties, including antibacterial, antifungal, and antitumor activities, as well as immuno-enhancing effects on animals. Conventional depolymerization methods of chitosan to chito-oligomers are either chemical by acid-hydrolysis under harsh conditions or by enzymatic degradation. In this work, hydrolysis of chitosan to chito-oligomers has been achieved by applying adsorption-separation technique using diluted HCl in the presence of different types of zeolite as adsorbents. The chito-oligomers were retrieved from adsorbents and characterized by differential scanning calorimetry (DSC), liquid chromatography/mass spectroscopy (LC/MS), and ninhydrin test.

Poly(thiolactone) homo- and copolymers from maleimide thiolactone: synthesis and functionalization

We describe the synthesis of a thiolactone-functionalized maleimide (MITla), its copolymerization into poly(thiolactone) homo- and copolymers via controlled or free radical polymerization (CRP or FRP) techniques, and subsequent modification.