Alessandro F. Martins

Antimicrobial Activity of Chitosan Derivatives Containing N-Quaternized Moieties in Its Backbone: A Review

Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial activity. However, chitosan applications as a biocide are only effective in acidic medium due to its low solubility in neutral and basic conditions. Also, the positive charges carried by the protonated amine groups of chitosan (in acidic conditions) that are the driving force for its solubilization are also associated with its antimicrobial activity. Therefore, chemical modifications of chitosan are required to enhance its solubility and broaden the spectrum of its applications, including as biocide. Quaternization on the nitrogen atom of chitosan is the most used route to render water-soluble chitosan-derivatives, especially at physiological pH conditions. Recent reports in the literature demonstrate that such chitosan-derivatives present excellent antimicrobial activity due to permanent positive charge on nitrogen atoms side-bonded to the polymer backbone. This review presents some relevant work regarding the use of quaternized chitosan-derivatives obtained by different synthetic paths in applications as antimicrobial agents.

Antiadhesive and Antibacterial Multilayer Films via Layer-by-Layer Assembly of TMC/Heparin Complexes

N-Trimethyl chitosan (TMC), an antibacterial agent, and heparin (HP), an antiadhesive biopolymer, were alternately deposited on modified polystyrene films, as substrates, to built antiadhesive and antibacterial multilayer films. The properties of the multilayer films were investigated by Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy, and Kelvin force microscopy. In vitro studies of controlled release of HP were evaluated in simulated intestinal fluid and simulated gastric fluid. The initial adhesion test of E. coli on multilayer films surface showed effective antiadhesive properties. The in vitro antibacterial test indicated that the multilayer films of TMC/HP based on TMC80 can kill the E. coli bacteria. Therefore, antiadhesive and antibacterial multilayer films may have good potential for coatings and surface modification of biomedical applications.

Characterization of N-trimethyl chitosan/alginate complexes and curcumin release.

N-trimethyl chitosan of two quaternization degrees, DQ=20 and 80mol% and labeled as TMC20 and TMC80, were synthesized and characterized by (1)H NMR. Polyelectrolyte complexes (PECs) of TMC/alginate (TMC/ALG) were prepared at pHs 2, 7 and 10 by mixing the aqueous solutions of unlike polymers. The PECs were characterized through infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTG) and wide-angle X-ray scattering (WAXS). Using the TMC of DQ=20 mol% and following the same methodology for preparing the PECs, beads of TMC20/ALG were obtained at pH 2 and loaded with curcumin (CUR) at pH 6.0-6.5. The morphology of the beads was evaluated by scanning electron microscopy (SEM). Studies in vitro of the controlled release of CUR from beads were investigated in simulated intestinal fluid (SIF) and simulated gastric fluid (SGF) and treated using conventional and partition-diffusion models. Results indicated that the beads based on TMC20 and ALG presented potential as drug-carrier to improve the solubility and biological activity of CUR at pH close to physiological one.

Chitosan/TPP microparticles obtained by microemulsion method applied in controlled release of heparin

This work deals with the preparation of chitosan/tripolyphosphate microparticles (CHT/TPP) using microemulsion system based on water/benzyl alcohol. The morphology of the microparticles was evaluated by scanning electron microscopy (SEM). The microparticles were also characterized through infrared spectroscopy (FTIR) and wide-angle X-ray scattering (WAXS). The morphology and crystallinity of microparticles depended mainly on CHT/TPP ratio. Studies of controlled release of HP were evaluated in distilled water and in simulated gastric fluid. Besides, the profile of HP releasing could be tailored by tuning the CHT/TPP molar ratio. Finally, these prospective results allow the particles to be employed as site-specific HP controlled release system.

Recent Advances in Food-Packing, Pharmaceutical and Biomedical Applications of Zein and Zein-Based Materials

Zein is a biodegradable and biocompatible material extracted from renewable resources; it comprises almost 80% of the whole protein content in corn. This review highlights and describes some zein and zein-based materials, focusing on biomedical applications. It was demonstrated in this review that the biodegradation and biocompatibility of zein are key parameters for its uses in the food-packing, biomedical and pharmaceutical fields. Furthermore, it was pointed out that the presence of hydrophilic-hydrophobic groups in zein chains is a very important aspect for obtaining material with different hydrophobicities by mixing with other moieties (polymeric or not), but also for obtaining derivatives with different properties. The physical and chemical characteristics and special structure (at the molecular, nano and micro scales) make zein molecules inherently superior to many other polymers from natural sources and synthetic ones. The film-forming property of zein and zein-based materials is important for several applications. The good electrospinnability of zein is important for producing zein and zein-based nanofibers for applications in tissue engineering and drug delivery. The use of zein’s hydrolysate peptides for reducing blood pressure is another important issue related to the application of derivatives of zein in the biomedical field. It is pointed out that the biodegradability and biocompatibility of zein and other inherent properties associated with zein’s structure allow a myriad of applications of such materials with great potential in the near future.

Preparation and cytotoxicity of N,N,N-trimethyl chitosan/alginate beads containing gold nanoparticles

Polyelectrolyte complex beads based on N,N,N-trimethyl chitosan (TMC) and sodium alginate (ALG) were obtained. This biomaterial was characterised by FTIR, TGA/DTG, DSC and SEM analysis. The good properties of polyelectrolyte complex hydrogel beads were associated, for the first time, with gold nanoparticles (AuNPs). Through a straightforward methodology, AuNPs were encapsulated into the beads. The in vitro cytotoxicity assays on the Caco-2 colon cancer cells and healthy VERO cells showed that the beads presented good biocompatibility on both cell lines, whereas the beads loaded with gold nanoparticles (beads/AuNPs) was slightly cytotoxic on the Caco-2 and VERO cells.

Curcumin-loaded dual pH- and thermo-responsive magnetic microcarriers based on pectin maleate for drug delivery

Magnetic microgels with pH- and thermo-responsive properties were developed from the pectin maleate, N-isopropyl acrylamide, and Fe3O4 nanoparticles. The hybrid materials were characterized by infrared spectroscopy, scanning electron microscope coupled with X-ray energy dispersive spectroscopy, wide angle X-ray scattering, Zeta potential, and magnetization hysteresis measurements. Curcumin (CUR) was loaded into the microgels, and release assays were carried out in simulated environments (SGF and SIF) at different conditions of temperature (25 or 37°C). A slow and sustainability CUR release was achieved under external magnetic field influence. Loaded CUR displayed stability, bioavailability and greater solubility regarding free CUR. Besides, the cytotoxicity assays showed that magnetic microgels without CUR could suppress the Caco-2 cells growth. So, the pectin maleate, N-isopropyl acrylamide, and Fe3O4 could be tailored to elicit hybrid-based materials with satisfactory application in the medical arena.

Synthesis, characterization, and cytotoxicity of TMC-graft-poly(vinyl alcohol) copolymers.

N-trimethyl chitosan-graft-poly(vinyl alcohol) (TMC-g-PVA) copolymers were prepared. The grafting reactions were conducted in water changing the feed ratios of poly(vinyl alcohol)/6-O-succinate-N-trimethyl chitosan (PVA/STMC). The structure of TMC-g-PVA copolymers was characterized through (1)H NMR spectroscopy, thermogravimetric analysis (TGA/DTG), wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM). The quaternization degree (DQ) and substitution degree (DS) of N-trimethyl chitosan (TMC) and 6-O-succinate-N-trimethyl chitosan (STMC) were determined by (1)H NMR, being the spectroscopy 14.0 and 5.5mol-% found, respectively. The viability of HCT-116 cancerous cells was investigated at different concentrations. The effect of PVA/STMC ratios on the cytotoxicity of the TMC-g-PVA copolymers was examined and the CC50 values determined for every case.

Preparation and cytotoxicity of N-modified chitosan nanoparticles applied in curcumin delivery.

Nanoparticles (NPs) based on N,N-dimethyl chitosan (DMC) and N,N,N-trimethyl chitosan (TMC), physical crosslinked with sodium tripolyphosphate (TPP) were successful obtained, using water/benzyl alcohol emulsion system. NPs morphologies were evaluated by Scanning Electron Microscopy and Transmission Electron Microscopy. NPs were characterized by Infrared Spectroscopy (FTIR), Thermogravimetric Analysis, Zeta Potential, Differential Scanning Calorimetry and Wide-angle X-ray Scattering. Curcumin (CUR) was loaded onto NPs and controlled release studies were evaluated in simulated intestinal fluid and in simulated gastric fluid. Cytotoxicity assays showed only loaded TMC/TPP particles containing CUR were slightly cytotoxic on human cervical tumor cells (SiHa cells), concerning unloaded TMC/TPP particles. Conversely, loaded NPs (TMC/TPP/CUR and DMC/TPP/CUR), especially TMC/TPP/CUR sample presented greater biocompatibility toward healthy VERO cells than unloaded NPs (TMC/TPP and DMC/TPP).

N,N-Dimethyl chitosan/heparin polyelectrolyte complex vehicle for efficient heparin delivery

Polysaccharide-based device for oral delivery of heparin (HP) was successfully prepared. Previously synthesized N,N-dimethyl chitosan (DMC) (86% dimethylated by (1)H NMR spectroscopy) was complexed with HP by mixing HP and DMC aqueous solutions (both at pH 3.0). The polyelectrolyte complex (PEC) obtention was confirmed by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTG) and wide-angle X-ray scattering (WAXS). In vitro controlled release assays of HP from PEC were investigated in the simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). The PEC efficiently protected the HP in SGF condition in which HP is degraded. On the other hand, in SIF PEC promoted the releasing of 80 ± 1.5% of loaded HP. The promissory results indicated that the PEC based on DMC/HP presented potential as drug-carrier matrix, since biological activity of HP was improved at pH close to physiological condition.