Juan Antonio Galbis

The present work deals with the synthesis of micro-structured biomaterials based on chitosan (CTS) for their applications as biocompatible carriers of drugs and bioactive compounds. Twelve dispersions were prepared by means of functional cross-linking with tricarballylic acid (TCA); they were characterized by Fourier transform infrared spectroscopy (FT-IR), modulated temperature differential scanning calorimetry (MTDSC) and scanning electron microscopy (SEM), and their rheological properties were studied. To the best of the authors’ knowledge, no study has been carried out on the influence of CTS concentration, degree of cross-linking and drug loading on chitosan hydrogels for drug delivery systems (DDS) and is investigated herein for the first time. The influence of dispersion composition (polymer concentration and degree of cross-linking) revealed to exert a marked impact on its rheological properties, going from liquid-like to viscoelastic gels. The release profiles of a model drug, diclofenac sodium (DCNa), as well as their relationships with polymer concentration, drug loading and degree of cross-linking were evaluated. Similar to the findings on rheological properties, a wide range of release profiles was encountered. These formulations were found to display a well-controlled drug release strongly dependent on the formulation composition. Cumulative drug release under physiological conditions for 96 h ranged from 8% to 67%. For comparative purpose, Voltaren emulgel^® from Novartis Pharmaceuticals was also investigated and the latter was the formulation with the highest cumulative drug release (85%). Some formulations showed similar spreadability values to the commercial hydrogel. The comparative study of three batches confirmed the reproducibility of the method, leading to systems particularly suitable for their use as drug carriers.

Micelles are good devices for use as controlled drug delivery systems because they exhibit the ability to protect the encapsulated substance from the routes of degradation until they reach the site of action. The present work assesses loading kinetics of a hydrophobic drug, pilocarpine, in polymeric micellar nanoparticles (NPs) and its pH-dependent release in hydrophilic environments. The trigger pH stimulus, pH 5.5, was the value encountered in damaged tissues in solid tumors. The new nanoparticles were prepared from an amphiphilic block copolymer, [(HEMA_19%-DMA_31%)-(FMA_5%-DEA_45%)]. For the present research, three systems were validated, two of them with cross-linked cores and the other without chemical stabilization. A comparison of their loading kinetics and release profiles is discussed, with the support of additional data obtained by scanning electron microscopy and dynamic light scattering. The drug was loaded into the NPs within the first minutes; the load was dependent on the degree of cross-linking. All of the systems experienced a boost in drug release at acidic pH, ranging from 50 to 80% within the first 48 h. NPs with the highest degree (20%) of core cross-linking delivered the highest percentage of drug at fixed times. The studied systems exhibited fine-tuned sustained release features, which may provide a continuous delivery of the drug at specific acidic locations, thereby diminishing side effects and increasing therapeutic rates. Hence, the studied NPs proved to behave as smart controlled drug delivery systems capable of responding to changes in pH.

The production of sustainable and environmentally friendly materials constitutes a growing field of attention. The incorporation of sugar‐derived units into traditional step‐growth polymers such as polyamides, polyesters, and polyurethanes is a healthy method to prepare novel biodegradable and biocompatible materials for application in the biomedical field and other sectors such as foodstuff packaging.

The copper(I)‐catalyzed alkyne‐azide cycloaddition (CuAAC) click polymerization has been used to obtain novel linear poly(ester triazole)s by reaction ofbis‐alkyne having ester linkage andbis‐azido monomers, most of them derived from carbohydrates, such as glucose, arabinose, and erythrose, and therefore coming from natural renewable resources. The resulting polyesters had weight‐average molecular weights in the 11,500–148,000 range and were characterized by GPC, IR, and NMR spectroscopies. Thermal studies revealed them to be amorphous and stable up to 200 °C under nitrogen. Degradation studies showed that they were hydrolytically degradable. These studies were carried out at 50 °C in phosphate buffer solution at pH 7.4, and were monitored by GPC, and NMR spectroscopy. Finally, novel network hydrogels were obtained by crosslinking reaction of the poly(ester triazole) chains with hexamethylene diisocyanate. The water absorption and the kinetic parameters of the networks were studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2015,53, 2481–2493

Copoly(amide triazole)s, abbreviated as PGBM_n, have been prepared by copolymerization of 6‐azido‐6‐deoxy‐2,3,4‐tri‐O‐methyl‐N‐(prop‐2‐yn‐1‐yl)‐d‐gluconamide and 6‐azido‐6‐deoxy‐2,3,4‐tri‐O‐benzyl‐N‐(prop‐2‐yn‐1‐yl)‐d‐gluconamide by catalyst‐ and solvent‐free 1,3‐dipolar Huisgen cycloaddition reaction. The resulting copolymers have a diblock or a random distribution of the monomeric units along the polymer chain. Their molecular weights are in the range of 70,000–90,000 and they were characterized by GPC and IR and NMR spectroscopies. Thermal studies revealed them to be amorphous and stable up to 200 °C under nitrogen. Their qualitative solubilities in various solvents and their water sorption have also been investigated. The copolymers are hydrophilic, one of them being water soluble. The in vitro hydrolysis of this copoly(amide triazole) was studied. The degradation study was carried out at 80 °C in buffered solution at pH 10, and was monitored by GPC, and NMR spectroscopy. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 413–421

A set of copolyesters (PHT_xGlux_y) with compositions ranging between 90/10 and 50/50 in addition to the parent homopolyesters poly(hexamethylene terephthalate) (PHT) and PHGlux, are prepared by the melt polycondensation of 1,6‐hexanediol (HD) with mixtures of dimethyl terephthalate (DMT) and dimethyl 2,4:3,5‐di‐O‐methylene‐d‐glucarate (Glux). The copolyesters have in the 35 000–45 000 g mol⁻¹ range, their microstructure is random, and they start to decompose at a temperature well above 300 °C. Crystallinity of PHT is repressed by copoly­merization so that copolyesters containing more than 20% of sugar‐based units are essentially amorphous. On the contrary, PHT_xGlux_y displays a T_g that increases monotonically with composition from 16 °C in PHT up to 73 °C in PHGlux. Compared with PHT, the copolyesters show an accentuated susceptibility to hydrolysis and are sensitive to the action of lipases upon incubation under physiological conditions. The degradability of PHT_xGlux_y increases with the content in Glux units. image