Resveratrol encapsulation in high molecular weight chitosan-based nanogels for applications in ocular treatments: Impact on human ARPE-19 culture cells.

Oxidative stress and inflammation play a pivotal role in ocular diseases. Resveratrol (RSV) is a natural bioactive that has recently attracted attention due to it potent antioxidant and anti-inflammatory properties. However, RSV presents poor aqueous solubility and chemical instability. Besides, effective drug delivery to the posterior segment of the eye is challenge. Nanotechnology emerges as a possible solution to improve both limitations. Here, we developed and characterized nanogels (NG) based on high molecular weight chitosan (HCS) crosslinked with sodium tripolyphosphate. The distribution size of NG presented a major population around 140 nm with a ζ-potential value of 32 ± 2 mV. TEM and AFM images showed that NG exhibited a rounded morphology. RSV encapsulation efficiency was 59 ± 1%. Photodegradation experiments showed that HCS by its own protects RSV from UV light-induced degradation. Biocompatibility assays revealed that NG were not cytotoxic neither inflammatory in human retinal pigment epithelial cells (ARPE-19), which constitutes the outer blood-retinal barrier. After cellular internalization, we report an endo-lysosomal escape of NG, which is crucial for efficient nanocarriers delivery systems. In conclusion, we envision that HCS based NG could constitute novel carriers for RSV, opening the possibility of its application in ocular diseases.

Bacterial nanocellulose production from naphthalene.

Polycyclic aromatic compounds (PAHs) are toxic compounds that are released in the environment as a consequence of industrial activities. The restoration of PAH-polluted sites considers the use of bacteria capable of degrading aromatic compounds to carbon dioxide and water. Here we characterize a new Xanthobacteraceae strain, Starkeya sp. strain N1B, previously isolated during enrichment under microaerophilic conditions, which is capable of using naphthalene crystals as the sole carbon source. The strain produced a structured biofilm when grown on naphthalene crystals, which had the shape of a half-sphere organized over the crystal. Scanning electron microscopy (SEM) and GC-MS analysis indicated that the biofilm was essentially made of cellulose, composed of several micron-long nanofibrils of 60 nm diameter. A cellulosic biofilm was also formed when the cells grew with glucose as the carbon source. Fourier transformed infrared spectroscopy (FTIR) confirmed that the polymer was type I cellulose in both cases, although the crystallinity of the material greatly depended on the carbon source used for growth. Using genome mining and mutant analysis, we identified the genetic complements required for the transformation of naphthalene into cellulose, which seemed to have been successively acquired through horizontal gene transfer. The capacity to develop the biofilm around the crystal was found to be dispensable for growth when naphthalene was used as the carbon source, suggesting that the function of this structure is more intricate than initially thought. This is the first example of the use of toxic aromatic hydrocarbons as the carbon source for bacterial cellulose production. Application of this capacity would allow the remediation of a PAH into such a value-added polymer with multiple biotechnological usages.

Naphthalene biodegradation under oxygen-limiting conditions: community dynamics and the relevance of biofilm-forming capacity.

Toxic polycyclic aromatic hydrocarbons (PAHs) are frequently released into the environment from anthropogenic sources. PAH remediation strategies focus on biological processes mediated by bacteria. The availability of oxygen in polluted environments is often limited or absent, and only bacteria able to thrive in these conditions can be considered for bioremediation strategies. To identify bacterial strains able to degrade PAHs under oxygen-limiting conditions, we set up enrichment cultures from samples of an oil-polluted aquifer, using either anoxic or microaerophilic condition and with PAHs as the sole carbon source. Despite the presence of a significant community of nitrate-reducing bacteria, the initial community, which was dominated by Betaproteobacteria, was incapable of PAH degradation under strict anoxic conditions, although a clear shift in the structure of the community towards an increase in the Alphaproteobacteria (Sphingomonadaceae), Actinobacteria and an uncultured group of Acidobacteria was observed in the enrichments. In contrast, growth under microaerophilic conditions with naphthalene as the carbon source evidenced the development of a biofilm structure around the naphthalene crystal. The enrichment process selected two co-dominant groups which finally reached 97% of the bacterial communities: Variovorax spp. (54%, Betaproteobacteria) and Starkeya spp. (43%, Xanthobacteraceae). The two dominant populations were able to grow with naphthalene, although only Starkeya was able to reproduce the biofilm structure around the naphthalene crystal. The pathway for naphthalene degradation was identified, which included as essential steps dioxygenases with high affinity for oxygen, showing 99% identity with Xanthobacter polyaromaticivorans dbd cluster for PAH degradation. Our results suggest that the biofilm formation capacity of Starkeya provided a structure to allocate its cells at an appropriate distance from the toxic carbon source.