Riccardo A.A. Muzzarelli

Chitosan stabilizes platelet growth factors and modulates stem cell differentiation toward tissue regeneration

The idea of using chitosan as a functional delivery aid to support simultaneously PRP, stem cells and growth factors (GF) is associated with the intention to use morphogenic biomaterials to modulate the natural healing sequence in bone and other tissues. For example, chitosan-chondroitin sulfate loaded with platelet lysate was included in a poly(D,L-lactate) foam that was then seeded with human adipose-derived stem cells and cultured in vitro under osteogenic stimulus: the platelet lysate provided to the bone tissue the most suitable assortment of GF which induces the osteogenic differentiation of the mesenchymal stem cells. PDGF, FGF, IGF and TGF-β were protagonists in the repair of callus fractures. The release of GF from the composites of chitosan-PRP and either nano-hydroxyapatite or tricalcium phosphate was highly beneficial for enhancing MSC proliferation and differentiation, thus qualifying chitosan as an excellent vehicle. A number of biochemical characteristics of chitosan exert synergism with stem cells in the regeneration of soft tissues.

6-Oxychitins, novel hyaluronan-like regiospecifically carboxylated chitins

Abstract Crustacean chitins and fungal chitin–glucan complexes are subjected to regiospecific oxidation at C-6 with NaOCl in the presence of Tempo® and NaBr at 25°C in aqueous solution. The resulting products have anionic character and are fully soluble over the entire pH range; they lend themselves to metal chelation, polyelectrolyte complex formation with a number of biopolymers including chitosan, and to microsphere and bead formation. 6-Oxychitin coagulates papain, lysozyme and other hydrolases active on chitosans. 6-Oxychitins of fungal and animal origins, in the form of free acids, salts and esters, might find use as surrogates of hyaluronans and of bacterial antigens in medical and health care products.

Emerging Biomedical Applications of Nano-Chitins and Nano-Chitosans Obtained via Advanced Eco-Friendly Technologies from Marine Resources

The present review article is intended to direct attention to the technological advances made in the 2010–2014 quinquennium for the isolation and manufacture of nanofibrillar chitin and chitosan. Otherwise called nanocrystals or whiskers, n-chitin and n-chitosan are obtained either by mechanical chitin disassembly and fibrillation optionally assisted by sonication, or by e-spinning of solutions of polysaccharides often accompanied by poly(ethylene oxide) or poly(caprolactone). The biomedical areas where n-chitin may find applications include hemostasis and wound healing, regeneration of tissues such as joints and bones, cell culture, antimicrobial agents, and dermal protection. The biomedical applications of n-chitosan include epithelial tissue regeneration, bone and dental tissue regeneration, as well as protection against bacteria, fungi and viruses. It has been found that the nano size enhances the performances of chitins and chitosans in all cases considered, with no exceptions. Biotechnological approaches will boost the applications of the said safe, eco-friendly and benign nanomaterials not only in these fields, but also for biosensors and in targeted drug delivery areas.

Interactions of chitin, chitosan, N-lauryl chitosan and N-dimethylaminopropyl chitosan with olive oil

Chitin, chitosan and the newly synthesized and fully characterized N-lauryl chitosan and N-dimethylaminopropyl chitosan, endowed with higher hydrophobicity and cationicity, respectively, were tested for their capacity to alter the composition of olive oil upon percolation of the latter through a bed of their respective powders. The oil samples were extracted, saponified and submitted to gas-chromatography. Results indicated that the percentages of 12 fatty acids were not modified, but the diacylglycerol and steroid concentrations were greatly altered. The percolated oil was depleted of C34 and C36 diacylglycerols (lowered to 42% of the control) when the oil was contacted with chitosan and N-lauryl chitosan, whilst the oil fraction percolated through chitin became 30% enriched. N-Dimethylaminopropyl chitosan was also effective in retaining diacylglycerols. The direct analysis of the unsaponifiable fraction revealed that campesterol, stigmasterol and avenasterol were enriched in the oil fraction retained by chitin and N-lauryl chitosan, while β-sitosterol increased slightly in the fraction retained by chitosan and N-lauryl chitosan. Triterpene alcohols were higher in the oil fraction retained by chitin. This work indicates that chitin might be more suitable than chitosan for sequestering steroids, and that, in general, the chitin derivatives discriminate among the various lipids.

Alkaline chitosan solutions.

Rigid and transparent hydrogels were obtained upon pouring chitosan salt solutions into saturated ammonium hydrogen carbonate. Incubation at 20 degrees C for 5 days yielded chitosan carbamate ammonium salt, Chit-NHCO(2)(-)NH(4)(+) a chemical species that either by hydrolysis or by thermal treatment decomposed to restore chitosan in free amine form. Chitosans of different degrees of acetylation, molecular sizes and origins (squid and crustaceans) were used as hydrochloride, acetate, glycolate, citrate and lactate salts. Their hydrogels obtained in ammonium hydrogen carbonate yielded chitosan solutions at pH values as high as 9.6, from which microspheres of regenerated chitosans were obtained upon spray-drying. These materials had a modest degree of crystallinity depending on the partial acylation that took place at the sprayer temperature (168 degrees C). Citrate could cross-link chitosan and impart insolubility to the microspheres. Chloride on the contrary permitted to prepare microspheres of chitosan in free amine form. By the NH(4)HCO(3) treatment, the cationicity of chitosan could be reversibly masked in view of mixing chitosan with alginate in equimolar ratio without coacervation. The clear and poorly viscous solutions of mixed chitosan carbamate and alginate were spray-dried at 115 degrees C to manufacture chitosan-alginate microspheres having prevailing diameter approx 2 micron.

In vivo and in vitro biodegradation of oxychitin–chitosan and oxypullulan–chitosan complexes

Oxychitin–chitosan complexes prepared from crustacean chitin and oxypullulan–chitosan complexes prepared from three different preparations of Aureobasidium pullulans pullulan were contacted with solutions of egg white lysozyme, Carica papaya papain, wheat germ lipase, Clostridium histolyticum collagenase, porcine pancreas α-amylase, barley malt α-amylase, and sweet potato α-amylase at nearly neutral pH values and 25 and 37°C, for at least three days. The reducing capacity of the solutions in contact with the complex, due to oligomer release, was measured with the aid of ferricyanide and expressed as net absorbance vs time. The oxychitin–chitosan complex was degraded by lysozyme, lipase and papain. The other enzymes were ineffective. Histological evidence indicated that the oxychitin–chitosan complex tested as a bone prosthesis coating in an animal model, was biochemically active and biodegradable, therefore capable to promote osteoconduction and greater bone formation at the bone-prosthesis interface, with no adverse effect on mineralization. Pullulans of different origins were susceptible to enzymatic hydrolysis, particularly so with animal amylase, nevertheless the chitosan complexes obtained from the corresponding oxypullulans were not degraded over the three-day observation period.