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In medical and pharmaceutical applications, chitosan is used as a component of hydrogels–macromolecular networks swollen in water. Chemical hydrogels are formed by covalent links between the crosslinking reagents and amino functionalities of chitosan. To date, the most commonly used chitosan crosslinkers are dialdehydes, such as glutaraldehyde (GA). We have developed novel GA like crosslinkers with additional functional groups–dialdehyde derivatives of uridine (oUrd) and nucleotides (oUMP and oAMP)–leading to chitosan-based biomaterials with new properties. The process of chitosan crosslinking was investigated in details and compared to crosslinking with GA. The rates of crosslinking with oUMP, oAMP, and GA were essentially the same, though much higher than in the case of oUrd. The remarkable difference in the crosslinking properties of nucleoside and nucleotide dialdehydes can be clearly attributed to the presence of the phosphate group in nucleotides that participates in the gelation process through ionic interactions with the amino groups of chitosan. Using NMR spectroscopy, we have not observed the formation of aldimine bonds. It can be concluded that the real number of crosslinks needed to cause gelation of chitosan chains may be less than 1%. [ABSTRACT FROM AUTHOR]

Poly(ethylene glycol) diglycidyl ether (PEG-DE) has been used as a crosslinker to construct artificial blood vessels of silk fibroin, endowing materials suitable compliance. As a biomaterial directly contacting with blood, it requires excellent anticoagulant property. In this article, hemolysis, platelet adhesion, platelet activity and plasma recalcification time of PEG-DE crosslinked silk fibroin were investigated using absorption spectrometry, scanning electron microscopy, methyl thiazolyl tetrazolium analysis and the time counting method. The hemolysis at ratios of PEG-DE crosslinked silk fibroin materials was < 0·5%, although it increased with increasing PEG-DE content. The platelet adhesion ratio and aggregation activity of PEG-DE crosslinked silk fibroin were higher than those of ethanol treated silk fibroin and increased with increasing PEG-DE content. However, the plasma recalcification time of PEG-DE crosslinked silk fibroin was longer than that of the ethanol treated silk fibroin and increased slightly with the increase of PEG-DE content. Based on these, PEG-DE used to crosslink silk fibroin showed different anticoagulant characteristics in different coagulation pathways. [ABSTRACT FROM AUTHOR]

A novel approach is presented for the synthesis of thermoresponsive and pH-sensitive magnetic nanohydrogels by using the biodegradable starch-maleate as a crosslinker and magnetic nanoparticles stabilizer. Chemically modified starch-maleate produces highly stable Fe3O4magnetic nanopaticles (MNPs) aqueous dispersion. Then,N-isopropylacrylamide (NIPAAm) and itaconic acid (IA) are successfully polymerized from the vinyl double bonds of the starch-maleate-MNPs to prepare the thermo- and pH-responsive magnetic nanohydrogels. The obtained PNIPAAm-g-(starch-MNPs) and (PNIPAAm-co-IA)-g-(starch-MNPs) nanohydrogels are characterized by transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectrometer, X-ray diffraction, differential scanning calorimetry, thermal gravimetric analysis, and vibrating sample magnetometer. Also, pH- and temperature-responsive behaviors of the synthesized magnetic nanohydrogels are investigated and, finally, the cytotoxicity and drug loading are examined with mitoxantrone (MTX) as an anticancer drug model. The results confirm the low toxicity and enhanced anticancer effect of MTX-loaded magnetic nanohydrogels. [ABSTRACT FROM AUTHOR]