Despite advanced sterilization and aseptic techniques, infections associated with medical implants have not been eradicated. Most present coatings cannot simultaneously fulfil the requirements of antibacterial and antifungal activity as well as biocompatibility and reusability. Here, we report an antimicrobial hydrogel based on dimethyldecylammonium chitosan (with high quaternization)-graft-poly(ethylene glycol) methacrylate (DMDC-Q-g-EM) and poly(ethylene glycol) diacrylate, which has excellent antimicrobial efficacy against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Fusarium solani. The proposed mechanism of the antimicrobial activity of the polycationic hydrogel is by attraction of sections of anionic microbial membrane into the internal nanopores of the hydrogel, like an 'anion sponge', leading to microbial membrane disruption and then microbe death. We have also demonstrated a thin uniform adherent coating of the hydrogel by simple ultraviolet immobilization. An animal study shows that DMDC-Q-g-EM hydrogel coating is biocompatible with rabbit conjunctiva and has no toxicity to the epithelial cells or the underlying stroma.

Facilely synthesized cationic peptidopolysaccharides, which have a bacterial peptidoglycan‐mimetic structure, show outstanding broad‐spectrum activities against clinically significant bacteria and fungi and low mammalian cytotoxicity. Their structural affinity with microbial cell‐wall constituents promotes penetration to reach the cytoplasmic membrane resulting in excellent antimicrobial activity and high selectivity.

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Chitosan and its various neutral pH water-soluble derivatives were investigated for dispersing single-walled carbon nanotubes (SWNTs). Chitosan (CS) can produce good dispersion of SWNTs, but only in acidic pH condition. Our two novel derivatives, O-carboxymethylchitosan (OC) and OC modified by poly(ethylene glycol) at the −COOH position (OPEG), were able to produce highly effective debundling and dispersion of SWNTs in neutral pH aqueous solution. Atomic force microscopy (AFM), transmission electron microscopy (TEM), photoluminescence, UV−vis−NIR spetroscopy, and Raman spectroscopy confirmed that SWNTs are present as individual nanotubes in the dispersions. The solubilities of individually dispersed SWNTs in neutral water are 0.021 and 0.032 g/L for OC and OPEG, respectively, which are comparable to 0.038 g/L for SWNTs using CS in acetic acid. Further, OC and OPEG aqueous solutions (1 wt %) do not significantly lower the surface tensions (65−67 mN/m). From the Fourier transform infrared spectroscopic results, we conclude that the free electron pair in the pendant amine groups of OC and OPEG plays a vital role in finely dispersing the SWNTs; the −NH2 contributes to the adsorption of these two chitosan derivatives on the nanotubes. Quaternary ammonium chitosan (QC), with alkyl substitution at the protonated amine, was found to be unable to disperse SWNTs; possibly cation−π interaction with nanotubes is diminished due to steric hindrance.

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Ionic hydrogels are attractive for the protection, delivery and controlled release of charged biomacromolecules such as proteins, growth factors or DNA. We have prepared and characterized a series of photocrosslinked anionic hydrogels based on water soluble methacrylated (MA) O‐carboxymethylchitosan (OCMCS) and polyethylene glycol (PEG) diacrylate. OCMCS samples with varying degree of substitution of carboxymethyl group ranging from 0.69 to 1.86 were prepared by reacting native chitosan with different amounts of monochloroacetic acid. The OCMCS products demonstrated differences in solubility, zeta potential (–52.7 to –12.8 mV) and thermal decomposition temperature (260 to 283 °C). The OCMCS products were then reacted with glycidyl methacrylate to make ultra‐violet (UV) crosslinkable OCMCS‐MAs which were blended with PEG diacrylate, a photoinitiator and water and successfully photocrosslinked to create OCMCS‐MA/PEG hydrogels. Water uptake of the hydrogels varied between 226 % to 358 % and the porous structures of the prepared OCMCS‐MA/PEG hydrogels could be modulated by the degree of methacrylation. All the OCMCS‐MA/PEG hydrogel substrates similarly supported attachment and proliferation of Smooth Muscle Cells (SMCs). The in vitro biodegradation of these hydrogels, in the presence of SMCs, could be controlled by the degree of methacrylation; weight loss after 9‐week was (15±1) % and (19±2) % using OCMCS 4‐MA (12.7 % MA) and OCMCS 1‐MA (4.6 % MA), respectively. In addition, the hydrogel based on the most anionic OCMCS 1 showed higher adsorption of basic TGF‐β1 than similarly modified ‐agarose, ‐dextran, and ‐chondroitin sulfate hydrogels.

Pure semiconducting single-walled carbon nanotubes (SWNTs) are appealing for many electronic circuits and devices, but the presence of parasitic metallic SWNTs in all as-synthesized nanotube samples makes this application elusive. Agarose gel electrophoresis (AGE) can be used to separate metallic from semiconducting SWNTs when applied in conjunction with the use of an appropriate surfactant or dispersant. To date, only sodium dodecyl sulfate (SDS) has been reported to permit considerable separation with AGE. In this study, we report on the considerably better separation achieved using chondroitin sulfate (CS-A) as a dispersant in AGE compared with SDS-assisted AGE. The CS-A assisted AGE technique may be used to produce in a single pass semiconducting SWNTs with purity of 95%, compared with 85% purity achieved with SDS-assisted AGE for the same arc discharge nanotubes. Further, the yield of CS-A assisted AGE is about 25%, which is in the order of 5 to 10 times the yields of other reported highly selective techniques. Semiconducting SWNTs produced via CS-A/AGE were used to fabricate field effect transistors (FET) with mobilities of ∼2 to 8 cm 2 /(V s) and on/off ratios from 10 2 to 10 5 , which are significantly higher than the mobility of 0.7 cm 2 /(V s), and on/off ratio of 10 4 reported for FETs made with semiconducting SWNTs produced by SDS-assisted AGE. The excellent yield-cum-purity single-pass separation is achievable with this unique chemically selective CS-A dispersant with AGE because of its ability to wrap the nanotubes well, high degree of sulfation making the nanotube/CS-A hybrid highly charged and amine functionality resulting in preselectivity of metallic nanotubes, causing the latter to migrate much more effectively under a uniform electric field.