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[Hmim][HSO4] ionic liquid (IL) and bio-renewable sources as chitosan (CHT) and chondroitin sulfate (CS) were used to yield hydrogel-based materials (CHT/CS). The use of IL to solubilize both polysaccharides was considered an innovative way based on "green chemistry" principle, aiming the production of CHT/CS blended systems. CHT/CS hydrogels were carried out in homogeneous medium from short dissolution times. The hydrogels were characterized and achieved with excellent stabilities (in the 1.2-10pH range), larger swelling capacities, as well as devoid of cytotoxicity towards the normal VERO and diseased HT29 cells. The CHT/CS hydrogels carried out in [Hmim][HSO4] could be applied in many technological purposes, like medical, pharmaceutical, and environmental fields.

Alginate/chitosan (ALG/CHT) and alginate/N,N-dimethyl chitosan (ALG/DMC) polyelectrolyte complex (PEC)-based adsorbents with high capacities for removing Pb(II) from aqueous systems are produced in [1-hydrogen-3-methylimidazolium hydrogen sulfate ionic liquid ([Hmim][HSO4―]). The [Hmim][HSO4―] is recovered, characterized by 1H NMR and reused to yield novel polysaccharide-based adsorbents. As-obtained PEC materials are characterized through infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and Zeta potential measurements. Kinetic and equilibrium adsorption studies reveal that the pseudo-second-order Kinetic, as well as the Redlich-Peterson isotherm, provide the best fits for the experimental data, respectively. CHT/ALG and DMC/ALG adsorbents promoted maximum adsorption capacities (qm) of 529.4 mg g−1 and 560.2 mg g−1, respectively. After adsorption, the materials are characterized by infrared spectroscopy and X-ray photoelectron spectroscopy, confirming that the chemisorption prevails upon Pb(II) removal. Also, PECs produced in the recovered [Hmim][HSO4―] have good capacities for removing Pb(II) ions from aqueous systems as well. This study showed that the [Hmim][HSO4―] is an alternative solvent to prepare novel and eco-friendly PEC-based adsorbents.

In this study, a surface modification strategy using natural biopolymers on titanium is proposed to improve bone healing and promote rapid and successful osseointegration of orthopedic implants. Titania nanotubes were fabricated via an anodization process and the surfaces were further modified with polyelectrolyte multilayers (PEMs) based on Tanfloc (a cationic tannin derivative) and glycosaminoglycans (heparin and hyaluronic acid). Scanning electron microscopy (SEM), water contact angle measurements, and X-ray photoelectron spectroscopy were used to characterize the surfaces. Adipose-derived stem cells (ADSCs) were seeded on the surfaces, and the cell viability, adhesion, and proliferation were investigated. Osteogenesis was induced and osteogenic differentiation of human ADSCs on the surfaces was evaluated via mineralization and protein expression assays, immunofluorescent staining, and SEM. The Tanfloc/heparin PEMs on titania nanotubes improved the rate of osteogenic differentiation of ADSCs as well as the bone mineral deposition, and is therefore a promising approach for use in orthopedic implants.

In this study, we show that the bactericidal activity of quaternized chitosans (TMCs) with sulfate, acetate, and halide counterions against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) correlates with the "availability" of N-quaternized groups [-(+)N(CH3)3] in the TMCs backbones. N,N,N-trimethyl chitosan sulfate (TMCS) and N,N,N-trimethyl chitosan acetate (TMCAc) displayed the highest activities, probably due to their delocalized π system. Among TMCs with halide counterions, activity was higher for N,N,N-trimethyl chitosan chloride (TMCCl), whereas N,N,N-trimethyl chitosan iodide (TMCI) and N,N,N-trimethyl chitosan bromide (TMCBr) exhibited lower, similar values to each other. This is consistent with the shielding of -(+)N(CH3)3 groups inferred from chemical shifts for halide counterions in (1)HNMR spectra. We also demonstrate that TMCs with distinct bactericidal activities can be classified according to their vibrational spectra using principal component analysis. Taken together, these physicochemical characterization approaches represent a predictive tool for the bactericidal activity of chitosan derivatives.

Processing stable polysaccharide membranes with suitable mechanical properties has been challenging for applications in wound healing and tissue engineering. Here we expand the characterization of pectin/chitosan (PT/CS) membranes (without covalent crosslinking), which we recently reported. Membranes containing pectin (PT) excess were formed, and PT/CS ratio can be tuned to enhance the mechanical strength, and to modulate hydrophilicity and cytocompatibility. The surface wettability and swelling properties of the polyelectrolyte complexes (PECs) played an important role to promote the attachment of stem cells. These PECs membranes have ultimate tensile strength similar to that of human skin, which is on the order of ten times higher than similar previously reported polysaccharide materials. We show for the first time that these new PT/CS membranes may promote anchorage, adhesion and support human stem cell growth, making them candidate materials for tissue engineering purposes.

Processing water-soluble polysaccharides, like pectin (PT), into materials with desirable stability and mechanical properties has been challenging. Here we report a new method to create water stable and mechanical resistant polyelectrolyte complex (PEC) membranes from PT and chitosan (CS) assemblies, without covalent crosslinking. This new method overcomes challenges of obtaining stable and durable complexes, by performing the complexation at low pH, enabling complex formation even when using an excess of PT, and when using PT with high degree of O-methoxylation. By performing the complexation at low pH, the complexes form with a high degree of intermolecular association, instead of forming by electrostatic complexation. This method avoids precipitation, and overcomes the aqueous instability typical of PT/CS complexes. After neutralization, the PEC membranes display features characteristic of a high degree of intermolecular association because of the self-assembling of polymer chains. The PT/CS ratio can be tuned to enhance the mechanical strength (σ = 39 MPa) of the membranes. These polysaccharide-based materials can demonstrate advantages over synthetic materials for technological applications.

New pectin derivative (Pec-MA) was obtained in specific reaction conditions. The presence of maleoyl groups in Pec-MA structure was confirmed by 1H NMR and FTIR spectroscopy. The substitution degree of Pec-MA (DS=24%) was determined by 1H NMR. The properties of Pec-MA were investigated through WAXS, TGA/DTG, SEM and zeta potential techniques. The Pec-MA presented amorphous characteristics and higher-thermal stability compared to raw pectin (Pec). In addition, considerable morphological differences between Pec-MA and Pec were observed by SEM. The cytotoxic effect on the Caco-2 cells showed that the Pec-MA significantly inhibited the growth of colon cancer cells whereas the Pec-MA does not show any cytotoxic effect on the VERO healthy cells. This result opens new perspectives for the manufacture of biomaterials based on Pec with anti-tumor properties.

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.

[Hmim][HSO

N , N , N -trimethyl chitosan (TMC) was synthesized through the N -methylation of chitosan (CHT) and characterized by FTIR and 1 H NMR spectroscopy. Polyelectrolyte complexes (PECs) based on TMC and heparin (HP) were prepared at different pHs (5, 8, 10 and 12) and characterized through FTIR spectroscopy, DSC and TGA curves and WAXS profiles. It was verified that the higher the pH of feed solution used for the PEC formation the higher is the thermal stability of PECs. Under basic conditions, the complexation between TMC and HP was more effective and alterations on WAXS profiles of PECs in relation to the precursor (TMC) were clearly observed. In addition, WAXS profiles show that the PEC crystallinity depends on the pH used for the complexation. These results are consistent with the FTIR, DSC, and TGA data. Due to the more intense electrostatic interactions, at higher pHs the unlike polymers chains (TMC and HP) are close enough to produce more stable PECs.