Ester Zuza

Coating of bioactive glass particles with mussel-inspired polydopamine as a strategy to improve the thermal stability of poly( l -lactide)/bioactive glass composites

Fabrication of bioactive glass (BG) filled polyester composites by traditional thermoplastic processing techniques is limited because a thermal degradation reaction occurs between the Si–O− groups present on the surface of the BG and the CO groups present in the backbone of the polymer at high temperatures. To overcome this problem, this study looked at the effect of mussel-inspired polydopamine (PDA) coated on the surface of BG particles. Thermogravimetric analysis demonstrated the improved thermal stability of poly(L-lactide) (PLLA) composites filled with PDA-coated BG particles compared to PLLA composites filled with uncoated BG particles. Moreover, these composites were successfully manufactured by hot-pressing, showing enhanced mechanical properties in comparison to non-coated BG filled PLLA composites. Dynamic mechanical analysis indicated a good interfacial interaction between PDA-coated BG particles and the PLLA matrix, suggesting that an immobilized layer of polymer chains was formed around the BG particles. Finally, the bioactivity of PLLA samples filled with 15 vol% of PDA-coated BG particles was confirmed via the deposition of an apatite layer on the surface of the material. In view of the results obtained it can be concluded that coating BG particles with PDA is a promising strategy as it can create composite materials with improved thermal stability and bioactivity.

Catechol End-Functionalized Polylactide by Organocatalyzed Ring-Opening Polymerization

There is a great interest in incorporating catechol moieties into polymers in a controlled manner due to their interesting properties, such as the promotion of adhesion, redox activity or bioactivity. One possibility is to incorporate the catechol as end-group in a polymer chain using a functional initiator by means of controlled polymerization strategies. Nevertheless, the instability of catechol moieties under oxygen and basic pH requires tedious protection and deprotection steps to perform the polymerization in a controlled fashion. In the present work, we explore the organocatalyzed synthesis of catechol end-functional, semi-telechelic polylactide (PLLA) using non-protected dopamine, catechol molecule containing a primary amine, as initiator. NMR and SEC-IR results showed that in the presence of a weak organic base such as triethylamine, the ring-opening polymerization (ROP) of lactide takes place in a controlled manner without need of protecting the cathechol units. To further confirm the end-group fidelity the catechol containing PLLA was characterized by Cyclic Voltammetry and MALDI-TOF confirming the absence of side reaction during the polymerization. In order to exploit the potential of catechol moieties, catechol end-group of PLLA was oxidized to quinone and further reacted with aliphatic amines. In addition, we also confirmed the ability of catechol functionalized PLLA to reduce metal ions to metal nanoparticles to obtain well distributed silver nanoparticles. It is expected that this new route of preparing catechol-PLLA polymers without protection will increase the accessibility of catechol containing biodegradable polymers by ROP.

Release mechanisms of urinary tract antibiotics when mixed with bioabsorbable polyesters

In depth knowledge of the thermal properties of drugs is particularly important when they are designed for incorporation into a thermoplastic polymer matrix. In this paper a representative set of Urinary Tract Infection (UTI) antibiotics were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and then blended via solvent-casting method with poly(D,L-lactide-co-ε-caprolactone). Of these, amoxicillin, cefdinir, levofloxacin and norfloxacin showed a co-continuous morphology with the polyester, whereas blends with ciprofloxacin, nitrofurantoin and tobramycin resulted in two immiscible phases. E. coli susceptibility results showed that the activity of these antibiotics was not affected by the interactions with the polymer matrix. The presence of the drug did not change the hydrolytic degradation kinetics of this fully amorphous polyester (KMw of ~0.050 days-1). However, the release profiles from the long-term studies (105 days) with a 10 or 30% of antibiotic-loaded films were quite different. While water was able to penetrate the polymer matrix and elute the entire levofloxacin content in the first 8 h, the burst release of cefdinir reached a value under 75%. A more interesting profile was obtained with nitrofurantoin, suggesting that a lengthy treatment is achievable. <30% of the drug was burst released, ~55% eluted by diffusion up to day 42 and the rest driven by the weight loss of the bioabsorbable polyester.

Biodegradable Polylactide‐Based Composites

The aim of this chapter is to introduce to the use and possible applications of polylactide‐based composites. Polylactides are biodegradable aliphatic polyesters, which are widely used in medical and ecological‐friendly fields. First of all, a deep description of main characteristics of polylactides is shown. This chapter summarizes many concepts, which comprehend a general view of polylactide biopolymers such as synthesis and structures, physical‐chemical and mechanical characterization and possible applications of final products. Then, an overview of composites based on polylactides and their benefits compared with bare polylactides are described.