Synthesis and characterization of temperature-sensitive cellulose-graft-poly(N-isopropylacrylamide) copolymers

Fabrication of Low-Temperature Fast Gelation β-Cyclodextrin-Based Hydrogel-Loaded Medicine for Wound Dressings

β-Cyclodextrin (β-CD) is often used as a drug carrier for biomedical materials due to its unique cavity structure. Herein, β-CD was modified by acryloyl chloride and further copolymerized with N-isopropylacrylamide (NIPAM) and acrylic acid (AA) to obtain PNIPAM-co-β-CD-AC. The results showed that the critical phase transition temperature of PNIPAM/β-CD-AC could be controlled at 19 °C, and the fast sol-gel phase transition was realized in 2-10 s. The hydrophobic drug carried in this hydrogel can constantly be released for more than 6 days at pH values (pH 5.5-8), and the duration may match the recovery of the wound. As a dressing hydrogel, its rapid gel formation and inversion as well as shear-thinning behavior prevent secondary wound damage. The β-CD-based hydrogel also has good biocompatibility and antioxidant properties, which provide a good potential choice for wound dressings, especially for exposed wounds in winter.

Fabrication and characterization of novel macroporous hydrogels based on the polymerizable surfactant AAc-Span80 and their enhanced drug-delivery capacity

In this study, macroporous pH-sensitive poly[N-isopropylacrylamide-co-acrylic acid-sorbitan monooleate] hydrogels, termed as PNIPAM-co-AAc-Span80 hydrogels, with an enhanced hydrophobic property and a rich pore structure were prepared by free-radical polymerization in an ethanol/water mixture. The polymerizable surfactant AAc-Span80 was obtained by the esterification of acrylic acid (AAc) and sorbitan monooleate (Span80), which was used to copolymerize with N-isopropylacrylamide (NIPAM). The chemical structure, thermal stability, morphology, and amphipathy of the PNIPAM-co-AAc-Span80 hydrogels were characterized. The results showed that the polymerizable surfactant AAc-Span80 macromolecule introduced into the hydrogels could not only increase the hydrophobic property but also ameliorate the porous network morphology, which was conducive to high adsorption capacity for adriamycin hydrochloride (DOX). The adsorption results showed that the equilibrium adsorption capacity of DOX reached 467.5 mg g⁻¹ within 48 h at pH 7.4, and the hydrophobic interactions and intermolecular hydrogen bonds were the main force in the adsorption process of DOX. The release results demonstrated that the macroporous pH-sensitive hydrogels loaded with DOX could release 98.7% of DOX at pH 5.0, which would be highly beneficial for the release of anti-cancer drugs in the environment of cancer cells. All the results demonstrate that the PNIPAM-co-AAc-Span80 hydrogels have great potential for the delivery of anti-cancer drugs.

PNIPAM-co-AAc-Span80 shows an enhanced hydrophobic property, rich pore structure, and good adsorption performance for DOX. The desorption results demonstrate that 98.7% of DOX can be released efficiently in an acidic environment.

Progress on chemical modification of cellulose in “green” solvents

Chemical modification of cellulose in "green" solvents.

Cellulose-based thermo-enhanced fluorescence micelles

Recently, cellulose-based stimuli-responsive nanomaterials have received significant attention because of its natural source and biocompatibility. In this study, cellulose-graft-poly(nisopropylacrylamide)-co-2-methyl-acrylic acid 2-carbazol-9-yl-ethyl ester (cellulose-g-(PNIPAAm&PCz)) block polymers were successfully synthesized by homogeneous atom transfer radical polymerization (ATRP) in LiCl/N,N-dimethylacetamide (DMAc) dissolution system. The block polymers showed different properties due to the different PCz content. The block polymer with low PCz content (cellulose-g-(PNIPAAm&PCz)1) was dispersed in water at 25 °C and self-assembled into micelles at 37 °C. On the other hand, the block polymer with high PCz content (cellulose-g-(PNIPAAm&PCz)2) was dissolved in DMF, THF, DMSO firstly, and dialyzed at 25 °C, 37 °C and 60 °C respectively to obtain the micelles. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) indicated that the distribution range of micelles formed by cellulose-g-(PNIPAAm&PCz)1 was narrower than cellulose-g-(PNIPAAm&PCz)2. And the sizes of the micelles formed by cellulose-g-(PNIPAAm&PCz)2 had little difference under different solvents, but became bigger with the temperature increased. The micelles displayed thermo-enhanced fluorescence due to the thermal-driven chain dehydration of the grafted PNIPAAm brushes, which is contrary to the decrease of the fluorescence of the monomer when the temperature increased. The results provided a potential for the application of cellulose-based stimuli-responsive micelles in the field of drug delivery and fluorescent probes.

Poly(N-isopropylacrylamide)/galactomannan from Delonix regia seed thermal responsive graft copolymer via Schiff base reaction

Aminated poly(N-isopropylacrylamide) (PNIPAm-NH₂) was grafted onto oxidized galactomannan polysaccharide extracted from Delonix regia (OXGM) via Schiff base reaction by a simple, rapid synthetic route, deprived of the use of organic solvents. Grafting was confirmed by FTIR and ¹H NMR and the self-organizing ability of the obtained nanoparticle copolymers was investigated by dynamic light scattering (DLS). The minimum concentration required for self-organization (CAC) at 25 °C was higher than at 50 °C. Lower critical solution temperature (LCST) was in the range 34-40 °C, depending on both inserted PNIPAm-NH₂ molar mass and on the presence of reduced imine bond. Synthesized copolymers are promising candidates for drug delivery as they show good cell viability, particle size around 250 nm and transition temperature closer to that of human body. Reaction success points out to the possibility of use free aldehyde groups of oxidized polysaccharide, not used in the copolymerization, to form a pro-drug with substances that possess NH₂ groups in their structure, such as doxorubicin.

A novel amino cellulose derivative using ATRP method: Preparation, characterization, and investigation of its antibacterial activity

In this study, we prepared a novel amino cellulose derivative (benzyl cellulose-g-poly [2-(N,N-Dimethylamino)ethyl methacrylate]) via a homogeneous ATRP method. The successful synthesis of the novel amino cellulose was confirmed by FT-IR and ¹H NMR. This study addressed the different characteristics of the prepared polymer including the thermal stability, solubility, and X-ray diffraction pattern. The antibacterial activity of the synthesized cellulose derivative was investigated using the diffusion disk method against both gram-negative (Escherichia coli, Salmonella enterica) and gram-positive (Staphylococcus aureus, Bacillus subtilis) bacteria. Based on the inhibition zone, it was confirmed that the prepared benzyl cellulose-g-PDMAEMA possesses acceptable antibacterial activity against Escherichia coli, Salmonella enterica, and Staphylococcus aureus while Bacillus subtilis is resistant to the prepared polymer. Also according to the inhibition zone, it was shown that benzyl cellulose-g-PDMAEMA has more impact on E. coli and Salmonella enterica than Staphylococcus aureus. Molecular dynamics simulation was also used to study the interaction of the synthesized cellulose derivative with a model membrane which presented atomistic details of the polymer-lipid interactions. According to the results obtained from the molecular dynamics simulation, the polymer was able to destabilize the structure of the membrane and clearly express its signs of degradation.

Injectable PNIPAM/Hyaluronic acid hydrogels containing multipurpose modified particles for cartilage tissue engineering: Synthesis, characterization, drug release and cell culture study

Novel injectable thermosensitive PNIPAM/hyaluronic acid hydrogels containing various amounts of chitosan-g-acrylic acid coated PLGA (ACH-PLGA) micro/nanoparticles were synthesized and designed to facilitate the regeneration of cartilage tissue. The ACH-PLGA particles were used in the hydrogels to play a triple role: first, the allyl groups on the chitosan-g-acrylic acid shell act as crosslinkers for PNIPAM and improved the mechanical properties of the hydrogel to mimic the natural cartilage tissue. Second, PLGA core acts as a carrier for the controlled release of chondrogenic small molecule melatonin. Third, they could reduce the syneresis of the thermosensitive hydrogel during gelation. The optimum hydrogel with the minimum syneresis and the maximum compression modulus was chosen for further evaluations. This hydrogel showed a great integration with the natural cartilage during the adhesion test, and also, presented an interconnected porous structure in scanning electron microscopy images. Eventually, to evaluate the cytotoxicity, mesenchymal stem cells were encapsulated inside the hydrogel. MTT and Live/Dead assay showed that the hydrogel improved the cells growth and proliferation as compared to the tissue culture polystyrene. Histological study of glycosaminoglycan (GAG) showed that melatonin treatment has the ability to increase the GAG synthesis. Overall, due to the improved mechanical properties, low syneresis, the ability of sustained drug release and also high bioactivity, this injectable hydrogel is a promising material system for cartilage tissue engineering.

Study on cellulose microfilaments based composite spheres: Microwave-assisted synthesis, characterization, and application in pollutant removal

A novel study of synthesizing the temperature-responsive polymer grafted cellulose filaments/Poly (N-isopropylacrylamide) (NIPAM) spheres (P-MCCBs) was carried out for the removal of dyes and heavy metal ions. The novelty of the presented work consists of the application of the nano-sized pore-forming agent (Calcium Carbonate) and the introduction of a temperature-responsive monomer (NIPAM) while preparing the adsorbents. In addition, the spherical adsorbents were synthesized through an in-situ free radical polymerization using a microwave-assisted heating approach. The morphology, chemical structure, pH, and thermal sensitivity of P-MCCBs were characterized properly. The adsorption and desorption behaviors of dyes and heavy metal ions on P-MCCBs were also investigated. The results showed that P-MCCBs exhibited a fast adsorption rate, the adsorption equilibrium reached within 80 min and 40 min for MB and Pb²⁺, respectively (25 °C). Moreover, around 5-8% and 20% of adsorbed MB and Pb²⁺ were released at the temperature above 45 °C. The adsorption kinetics followed pseudo-second-order model, and the desorption process was fit well using Higuchi and Korsmeyer-Peppas models. These results indicated that P-MCCBs could be served as a novel material for controllable adsorption and desorption processes of various contaminants.