Sérgio P. Campana-Filho’s research while affiliated with University of São Paulo and other places

Multidrug-resistant bacteria represent a global health and economic burden that urgently calls for new technologies to combat bacterial antimicrobial resistance. Here, we developed novel nanocomposites (NCPs) based on chitosan that display different degrees of acetylation (DAs), and conjugated polymer cyano-substituted poly(p-phenylene vinylene) (CNPPV) as an alternative approach to inactivate Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria. Chitosan’s structure was confirmed through FT-Raman spectroscopy. Bactericidal and photobactericidal activities of NCPs were tested under dark and blue-light irradiation conditions, respectively. Hydrodynamic size and aqueous stability were determined by DLS, zeta potential (ZP) and time-domain NMR. TEM micrographs of NCPs were obtained, and their capacity of generating reactive oxygen species (ROS) under blue illumination was also characterized. Meaningful variations on ZP and relaxation time T2 confirmed successful physical attachment of chitosan/CNPPV. All NCPs exhibited a similar and shrunken spherical shape according to TEM. A lower DA is responsible for driving higher bactericidal performance alongside the synergistic effect from CNPPV, lower nanosized distribution profile and higher positive charged surface. ROS production was proportionally found in NCPs with and without CNPPV by decreasing the DA, leading to a remarkable photobactericidal effect under blue-light irradiation. Overall, our findings indicate that chitosan/CNPPV NCPs may constitute a valuable asset for the development of innovative strategies for inactivation and/or photoinactivation of bacteria.

ANTIMICROBIAL ACTIVITY OF CHITOSAN AND ITS DERIVATIVES: INFLUENCE OF ITS STRUCTURAL CHARACTERISTICS. In recent years, there has been an increasing interest in the development of antimicrobial materials for different applications, especially in the biomedical field. In this context, chitosan is one of the most employed materials due to its highly attractive properties, such as biocompatibility, biodegradability, non-toxicity, and antimicrobial activity against gram-negative and gram-positive bacteria and fungi. In this review, we discuss the different methods used to obtain chitosan and point out how they affect the structural and chemical properties of this material, followed by a detailed discussion on how these properties influence its antimicrobial activities. Additionally, we summarize the most accepted antimicrobial mechanisms of action for chitosans. Specifically, we aim to provide a comprehensive overview on the last findings and progress reported in the literature on the factors that influence the antimicrobial activity of chitosan, e.g., polymeric average molecular weight (MV ), average degree of acetylation (DA), water-soluble derivatization and sample degree of purity. The data available in the literature indicate that in addition to the structural properties, the effectiveness of such antimicrobial activity of chitosan is also dependent on the target microorganisms. This review will help researchers to better understand the mechanism of action of chitosan against microorganisms based on its structural characteristics.

The aim of this work was to investigate the potential of a new 3,6-O,O'-dimyristoyl derivative amphiphilic chitosan (DMCh), in improving the solubility of camptothecin (CPT), a hydrophobic anticancer drug, and its potential oral delivery. FTIR, 1 H NMR and solid-state 13 C NMR spectroscopy were used to characterize DMCh and to determine its average degree of substitution (̅̅̅̅ = 6.8 %). DMCh/CPT micelles size ranged from (281-357 nm), zeta potential (+32-50 mV) of encapsulation efficiency of 42-100%. The in vitro cell viability showed that DMCh/CPT micelles were able to reduce the toxicity of CPT. The in vitro permeability of CPT through Caco-2 and Caco-2/HT29-MTX intestinal models was increased up to ten fold when formulated into DMCh micelles, underlining the mucoadhesive properties of the nanocarrier. DMCh/CPT micelles are able to enhance CPT solubility and bioavailability while reduce its cytotoxicity, showing the great potential for intestinal delivery of hydrophobic drugs.

This study applied the use of marine-derived fungus Penicillium citrinum CBMAI 1186 in the stereoselective reduction of the C=C double bond of the prochiral (E)-2-methyl-3-phenylacrylaldehyde 1. The fungus immobilized on chitosan, obtained by multistep ultrasound-assisted deacetylation process (Ch-USAD), produced the (S)-(+)-2-methyl-3-phenylpropan-1-ol 3 (c = 49%, 40% ee) isomer and (±)-2-methyl-3-phenylacrilic acid 4 (c = 35%); in contrast, immobilized mycelia on commercial chitosan (Ch-C) yielded the (S)-(+)-2-methyl-3-phenylpropan-1-ol 3 (c = 48%, 10% ee) and (±)-2-methyl-3-phenylpropanal 1a (c = 41%). The reaction using free mycelia gave a 40% yield of (S)-(+)-2-methyl-3-phenylpropan-1-ol 3 with 10% ee. These results showed that the crystallinity form and molecular weight of chitosan (Ch-C or Ch-USAD) used to immobilized mycelia of P. citrinum CBMAI 1186 influenced in the biotransformation of (E)-2-methyl-3-phenylacrylaldehyde 1. Therefore, marine-derived fungus P. citrinum CBMAI 1186 immobilized on chitosan can be a potential alternative in the studies of hydrogenation of the α,β-unsaturated carbon-carbon (α,β-C=C) double bond. Marine-derived fungus Penicillium citrinum CBMAI 1186 immobilized on chitosan in the stereoselective reduction of the C=C double bond of the prochiral (E)-2-methyl-3-phenylacrylaldehyde

Miniaturized and inexpensive sensing platforms remains an important goal for the field-deployable monitoring of toxic gases. In this work, we report a disposable ethanol sensor based on nanochitin-composite containing chitin nanowhiskers/zinc oxide nanoparticles/polyaniline (ChitNW-ZnO/PANI) produced via solution casting method. The as-prepared material was fully characterized by transmission electron microscopy, atomic force microscopy, contact angle measurements, thermogravimetric analysis and X-ray diffraction, confirming its successful preparation and revealed its morphology, microstructure and composition. Such nanocomposite shows enhanced ethanol sensing performance at room temperature. Quantitative analysis was obtained in the range 20 - 100 ppm with a detection limit of 17 ppm (S/N = 3). We further validated that common potential interfering agents are not misidentified with ethanol. Development of such a unique nanochitin-based composite as a disposable sensor is a great step ahead in flexible and wearable electronics having potential applications in different fields such as biomedical, security and Internet of things.

Langmuir monolayers have been used as cell membrane models, where lipid composition is normally varied to mimic distinct types of membranes. For eukaryotic membranes, for instance, rather than using only zwitterionic phospholipids there is now a trend to employ mixtures to simulate the lipid rafts known to be relevant for various cellular processes. In this study, we demonstrate that effects from chitosans on Langmuir monolayers are considerably higher if lipid raft compositions (ternary mixtures of dipalmitoyl phosphatidyl choline (DPPC), sphingomyelin (SM) and cholesterol) are used. Significantly, measurable effects on the surface pressure isotherms start at 10⁻⁶ mg/mL for chitosans in lipid rafts, to be compared with 10⁻² mg/mL for neat dipalmitoyl phosphatidylcholine (DPPC). This applies to both a commercial chitosan and chitosans soluble at physiological pH. Incorporation of these chitosans in the raft monolayers was confirmed in polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) experiments, where both the tail groups and headgroups were found to interact with chitosan. Since the effects on membrane models may be observed at such small concentrations for chitosans and probably other molecules, some studies may have to be revisited where neat phospholipids should be replaced by lipid raft compositions.

The demand for low cost and effective materials to remove contaminants such as residues of oil spills has encouraged studies on new biosorbents produced from wastes. Considering the overgeneration of fishing residues and the necessity to provide an alternative purpose for such materials, this study aimed to evaluate squid gladius and its derivatives (β-chitin and chitosan) as sorbents to remove marine diesel oil (MDO) from fresh and artificial seawater. It was also executed an attempted to improve their performances through a high-intensity ultrasound treatment (UT-gladius and UT-β-chitin). All sorbents removed MDO at both salinities. Contact surface area, salinity, and water retention seemed to play a key role in the outcomes. UT-β-chitin’s performance was significantly superior to β-chitin’s and chitosan’s in MDO removal at salinity 0, as well as at salinity 30, where gladius and UT-gladius also excelled. Ultrasound treatment improved the oil removal performance of UT-β-chitin by increasing its contact surface area. This is the first report on the efficiency of gladius and UT-β-chitin for such purpose, and brought up huge possibilities and new questions that can lead to the achievement of biosorbents of great efficiency.