Preparation and characterization of antibacterial, antioxidant, and biocompatible p-coumaric acid modified quaternized chitosan nanoparticles.

To fabricate multifunctional nanoparticles (NPs) based on chitosan (CS) derivative, we first prepared quaternized CS (2-hydroxypropyltrimethyl ammonium chloride CS, HTCC) via a one-step approach, then synthesized p-coumaric acid (p-CA) modified HTCC (HTCC-CA) for the first time through amide reaction, and finally fabricated a series of NPs (HTCC-CA NPs) using HTCC-CAs with different substitution degrees and sodium tripolyphosphate (TPP) by ionic gelation. Newly-prepared HTCC and HTCC-CAs were characterized by FT-IR, 1H NMR, elemental analysis (EA), full-wavelength UV scanning, silver nitrate titration, and Folin-Ciocalteu methods. DLS and TEM results demonstrated that three selected HTCC-CA NPs had moderate size (< 350 nm), good dispersion (PDI < 0.4), and positive zeta potential (11-20 mV). The HTCC-CA NPs had high antibacterial activity against six bacterial strains, and the minimum inhibitory concentration (MIC) values were almost the same as the minimum bactericidal concentration (MBC) values (250-1000 µg/mL). Also, the HTCC-CA NPs had good antioxidation (radical scavenging ratio > 65 %) and low cytotoxicity (relative cell viability >80 %) to the tested cells. Totally, HTCC-CA NPs with high antibacterial activity, great antioxidation, and low cytotoxicity might serve as new biomedical materials for promoting skin wound healing.

Carboxymethyl chitosan and carboxymethyl cellulose based self-healing hydrogel for accelerating diabetic wound healing.

In this study, a new type of biodegradable, injectable, self-healing, and low-toxic CMCSH, formed by N, O-carboxymethyl chitosan-heparin (CMCS-Hep) and carboxymethyl cellulose-aldehyde (CMC-A), was designed to deliver drug for promoting the progress of the diabetic wound healing. CMCS was modified with Hep for the first time to synthesize CMCS-Hep, and CMC-A was synthesized by the periodate oxidation method. First, SOD encapsulated in the CMCSH was applied to the diabetic wound bed to moderate the microenvironment, then rhEGF retained in the CMCSH was sustainedly released to the wound area. These results indicated that the dual-drug delivery system had the ability to improve drug availability, promote cell migration and proliferation, reduce DNA damage, shorten the inflammatory period, and accelerate the deposition of collagen fibers and the formation of blood vessels in the model with diabetic skin injury, suggesting that CMCSH as drug carriers had positive effects on diabetic wound healing.

Antibacterial porous sponge fabricated with capric acid-grafted chitosan and oxidized dextran as a novel hemostatic dressing.

This work aims to fabricate multifunctional hemostatic sponges (C-ODs). Porous C-ODs were first constructed by using capric acid-modified chitosan (CSCA) and oxidized dextrans (ODs) with different oxidation degrees. Batches of experiments showed that (i) CSCA (33.39% of grafting degree), ODs, and C-ODs (100-200 µm in pore size) were synthesized, evidenced by FT-IR, 1H NMR, elemental analysis, hydroxylamine hydrochloride titration, and SEM results; (ii) among C-ODs, C-OD2 had appropriate porosity (85.0%), swelling (20 times its dry weight), absorption, water retention, water vapor transmission, and mechanical properties; (iii) C-OD2 possessed low toxicity (relative cell viability > 86%), low hemolysis rate (0.65%), suitable tissue adhesion (4.74 kPa), and strong antibacterial efficacy (five strains); and (iv) C-OD2's dynamic blood clotting was within 30 s. In three animal injury models, C-OD2's hemostasis time and blood loss were fairly lower than commercial gelatin sponge. Totally, C-OD2 might serve as an ideal hemostatic dressing.

Novel amidinothiourea-modified chitosan microparticles for selective removal of Hg(II) in solution.

Glutaraldehyde-crosslinked chitosan microparticles (CGP) prepared via the inversed-phase emulsification were successively modified by epichlorohydrin (ECH) and amidinothiourea (AT) as novel adsorbent (CGPET) for selective removal of Hg(II) in solution. FTIR, EA, XPS, SEM-EDX, TG, DTG, and XRD results indicated that CGPET had ample -NH2 and CS, relative rough surface, mean diameter of ~40 µm, great thermal stability, and crystalline degree of 2.4%, beneficial to the uptake of Hg(II). The optimum parameters (pH 5, dosage 1 g/L, contact time 4 h, and initial concentration 150 mg/L) were acquired via batches of adsorption experiments. Adsorption behavior was well described by the Liu isothermal and pseudo-second-order kinetics models, and the maximum adsorption capacity was 322.51 mg/g, surpassing many reported adsorbents. Regeneration and coexisting-ion tests demonstrated that CGPET had outstanding reusability (Rr > 86.89% at the fifth cycle) and selectivity (Rs > 93%). Besides, its potential adsorption sites and mechanisms were proposed.

Cr(VI) and Pb(II) capture on pH-responsive polyethyleneimine and chloroacetic acid functionalized chitosan microspheres.

PEI-ECH-CMCS microspheres (MPs) were first constructed via elaborately programmed procedures. Fourier transform infrared spectroscopy, conductometric titration, Brunauer-Emmett-Teller, X-ray diffraction, pH at zero point of charge (pHzpc), scanning electron microscopy, X-ray photoelectron spectroscopy, and swelling results demonstrated that chitosan-based adsorbent had ample -NH2 and -COOH, specific surface area of 29.040 m2/g, porous 3D architectures, pHzpc of 4.2, uniform spherical surfaces, narrow size distribution (19-33 µm), and pH-responsive swelling features, advantageous to Cr(VI) and Pb(II) capture. Adsorption parameters were obtained from batch experiments and pH 3 and 5 were chosen for Cr(VI) and Pb(II) capture. Pseudo-second-order kinetic and Liu isotherm models well interpreted adsorption behavior, and thermodynamic, isotherm, and kinetic studies revealed an exothermic, spontaneous, monolayer, and chemical adsorption process. Maximum adsorption capacity for Cr(VI) or Pb(II) was 331.32 or 302.56 mg/g, exceeding CS-based adsorbents reported. Excellent reusability and feasibility were evidenced by adsorption capacity loss < 12.10% and high removal efficiency for Cr(VI) (95.79%) and Pb(II) (91.40%) in synthetic effluents. Finally, potential adsorption mechanisms were proposed.