Synthesis and aqueous solution behavior of phosphonate-functionalized chitosans

Phosphonate-chitosan functionalization of a multi-channel hydroxyapatite scaffold for interfacial implant-bone tissue integration

Phosphonate-chitosan functionalization of a multi-channel hydroxyapatite scaffold as a new approach to improve interfacial implant-bone tissue integration.

pH-Responsive polymers

This review summarizes pH-responsive monomers, polymers and their derivative nano- and micro-structures including micelles, cross-linked micelles, microgels and hydrogels.

Controlled synthesis of N,N,N-trimethyl chitosan for modulated bioadhesion and nasal membrane permeability

In an experiment to explore the bioadhesion, biocompatibility, and membrane permeation properties, the controlled synthesis of N,N,N-trimethyl chitosan (TMC) was carried out by two-step reductive methylation of chitosan (CHT). Methylation was confirmed by (1)H NMR (δ=3.1 ppm) and FTIR analysis (CH stretch at 1,485 cm(-1)). The TMC was further characterized by DSC, TGA, XRD, HR-TEM, SEM, and elemental analysis. Findings revealed improved solubility, enhanced viscosity, increased swelling index and higher molecular weight of TMC over CHT. Comparative evaluation validated increased bioadhesion potential, and improved ex vivo biocompatibility of TMC compared to CHT. Increased bioadhesion of TMC NPs over CHT NPs can be attributed to the strong electrostatic interactions between cationic amino groups with anionic sialic and sulfonic acid moieties contained in the mucin of the nasal mucus. Ex vivo biocompatibility studies suggested that the NP formulations of both biopolymers were biocompatible and could be applied safely on the nasal epithelium. Ex vivo permeation studies executed on excised cattle nasal mucosa illustrated improved permeability of TMC NPs over CHT NPs. In the author's opinion, two-step reductive methylation of CHT could be an attractive strategy to improve its solubility, bioadhesion, and permeation characteristics without affecting biocompatibility across the mucosal surfaces.

Phosphorylation of bio-based compounds: the state of the art

The aim of this review is to present both fundamental and applied research on the phosphorylation of renewable resources, through reactions on naturally occurring functions, and their use in biobased polymer chemistry and applications.

New prospects for the synthesis of N-alkyl phosphonate/phosphonic acid-bearing oligo-chitosan

Water-soluble oligo-chitosan were functionalized with N-alkyl phosphonate/phosphonic acid groups via Kabachnik-Fields and epoxy-amine reactions.

Biodegradable 'intelligent' materials in response to chemical stimuli for biomedical applications

BACKGROUND

Biodegradable stimuli-responsive materials, which exhibit large and sharp physical-chemical changes in response to small physical or chemical stimuli, are attracting increasing interests because of their potential applications in biomedical fields, such as transient implants, drug delivery carriers, and tissue engineering scaffolds. Our previous review (see page 493 of issue 4) summarized those biodegradable 'intelligent' materials that respond to physical stimuli, such as temperature, ultrasound, and magnetic field. Biodegradable 'intelligent' materials that could respond to chemical stimuli, such as pH and specific molecules, have also been studied intensively and significant progress in this field has been achieved. As a single stimulus-responsive property would limit practical application, multi-stimuli-responsive materials are receiving increasing interest and considerable attention.

OBJECTIVE/METHODS

This review summarizes the development of biodegradable 'intelligent' materials in response to chemical stimuli and to dual stimuli; their potential biomedical applications are also introduced. A detailed analysis of publications and patents on such materials in recent years is presented.

RESULTS/CONCLUSION

Most of biodegradable stimuli-responsive materials are currently still at a developmental research stage. Further work is required to improve the responsive properties between the materials and the biological environments, so that the clinical applicability of such devices could be successful. We hope that our review will be helpful in the future development of new stimuli-responsive biodegradable polymers or polymeric systems that can be used reliably in real-life applications.

Synthesis, characterization and thermal sensitivity of chitosan-based graft copolymers

Novel chitosan-based graft copolymers (CECTS-g-PDMA) were synthesized through homogeneous graft copolymerization of (N,N-dimethylamino)ethyl methacrylate (DMA) onto N-carboxyethylchitosan (CECTS) in aqueous solution by using ammonium persulfate (APS) as the initiator. The effect of polymerization variables, including initiator concentration, monomer concentration, reaction time and temperature, on grafting percentage was studied. XRD, FTIR, DSC and TGA were used to characterize the graft copolymers. Surface-tension measurements, turbidity measurements and temperature-variable (1)H NMR analysis were combined to investigate the thermal sensitivity of CECTS-g-PDMAs in aqueous solution.