Hydrolysis of poly(l‐lactide)/ZnO nanocomposites with antimicrobial activity

Abstract

This work investigates the effect of the incorporation of zinc oxide (ZnO) nanoparticles within a poly(L-lactic acid) (PLLA) matrix as an approach to speed up the hydrolysis of PLLA film surfaces. Hydrolysis was done by immersing nanocomposite films having 1 wt % of ZnO in 0.25 M sodium hydroxide at 58 C. This concentration has been selected as it provides the maximum changes of physicochemical properties of hosting PLLA matrix. The evolution of the thermal properties, ultraviolet-visible transparency, wettability, and morphology were monitored at different time points. The amount of carboxylic groups onto PLLA/ZnO surfaces was quantified according to Toludine Blue-O assay. Hydrolysis was mainly limited to film surfaces, which were grafted by carboxylic groups as a result of the random scission of PLLA ester linkages. The presence of such functional groups decreases the inherent surface hydrophobicity of PLLA at short hydrolysis times. On the contrary, long hydrolyses increase the hydrophobicity as a result of surface nanostructuring induced by the degradation of PLLA to water-soluble oligomers. Overall, ZnO nanoparticles enable shorter surface modification times and provide a quick approach for the modification on the polarity of polylactide surfaces. The potential of hydrolyzed films as antimicrobial materials was explored using Gram-negative Escherichia coli as a model. Accordingly, materials used for packaging applications should be transparent in the visible region at the same time that they display a good degradability, proper mechanical performance, low toxicity, environmentally benign characteristics, ultraviolet (UV)-shielding properties, antibacterial activity, and cost competitive characteristics. Polylactides (PLAs) fulfill the majority of those requirements and they represent one of the most remarkable examples of biopolymers able to replace petroleum-based materials. [1][2][3][4] PLAs are linear aliphatic polyesters that could be obtained from 100% renewable Additional Supporting Information may be found in the online version of this article.

Hydrolytic depolymerisation of polyesters over heterogeneous ZnO catalyst

“…A mechanism for the hydrolytic degradation of antimicrobial PLA/ZnO nanocomposites, in phosphate buffered or in NaOH solutions, has been proposed. 75 Analogously to the above literature, the Zn centres were hypothesized to act as Lewis acid activators of the carbonyl ester bond, which then undergoes a nucleophile attack by water. In another report, it was suggested that the hydrolysis of PLA/ZnO nanocomposites occurs via anchoring of the acid end groups of PLA on a hydroxylated ZnO surface, followed by attack of the ester bond by hydroxyl anions.…”

Strategies to Enhance Biomedical Device Performance and Safety: A Comprehensive Review

“…For polymers, it is important to ensure that the concentration and treatment duration of the acidic/alkali solution do not significantly alter the bulk properties of the underlying polymer. Additionally, in both cases, the nonspecific nature of the treatment can lead to irregular surface degradation, potentially affecting the overall surface integrity and properties of the modified material [58,79]. Therefore, careful optimization of the hydrolysis process is essential to achieve desired modifications while preserving the core properties of the substrate.…”

New-generation osteoplastic materials based on biological and synthetic matrices

“…Оксид цинка в составе остеопластического матрикса ингибирует прикрепление бактерий и стимулирует дифференцировку клеток в направлении фенотипа миоцитов [85]. При интеграции оксида в композитную систему PLLA/ZnO (ZnO в виде наностержней ~40 нм), композит медленно выделяет ионы цинка в окружающую среду [86].…”

“…Наностержни действуют как каталитические ядра, слегка ускоряя деградацию полимера. Это наблюдение имеет ключевое значение поскольку улучшает связь между дифференцированными миоцитами и имплантатом [85].…”