Protocol: https://doi.org/10.5281/zenodo.6970130 

Background: Bacterial resistance to multiple drugs is a worldwide problem that afflicts public health. This is why nanomedicine approach has been used to combat the antibiotic resistance, among them is the synthesis of silver nanoparticles. Various studies have shown that silver nanoparticles are good bactericidal agents against Gram negative and Gram positive bacteria due to the adherence and penetration of the external bacterial membrane, preventing different vital functions and subsequently bacterial cell death.

Methods: We searched the following databases: ScienceDirect, PubMed, Scopus, and EBSCOhost. The quality of the articles was assessed using the Retraction Watch Database, and the review was carried out in accordance with the PRISMA ScR 2020 guidelines. This review aims to answer the following question: In which type of drug-resistant bacteria (Gram positive or Gram negative) are silver nanoparticles more effective as bactericides?

Results: Out of the initial 1420, 141 studies met the inclusion criteria and were included to form the basis of the analysis. The results of this systematic review showed that silver nanoparticles act primarily as bacteriostatic agents and subsequently as bactericides, both in Gram-positive and Gram-negative drug-resistant bacteria. In addition, the synthesis method using phytochemical reducers as well as physicochemical properties, such as size distribution, could be related to bacteriostatic/bactericidal activity. 

Conclusions: Silver nanoparticles are more effective as bactericide in Gram negative bacteria. More preclinical studies with controls are necessary to elucidate the benefits of using silver nanoparticles as bactericide agents in different drug-resistant bacteria infections.

Protocol: https://doi.org/10.5281/zenodo.4741321 

Background: Drug delivery systems have been developed to treat diseases associated with the eye. However, one of the greatest challenges is to improve routes of administration, specifically the periocular and intravitreal, have the blood-retinal barrier as the greatest impediment. Lipid nanoparticles as a nucleic acid delivery system have been used as an alternative to treat ocular diseases, since they can cross the ocular barrier and efficiently transfecting nucleic acids to various cells of the eye. The size influences the transfection of genes, biological distribution, diffusion, and cellular uptake, so there are several factors that influence the characterization of the desired size for the nanoparticle. Several reported investigations vary in particle size and encapsulation efficiency, and a relationship between these variables has not been reported so far. Therefore, we propose the research question: What size of lipid nanoparticles targeting eye diseases has a higher encapsulation efficiency depending on the type of encapsulated nucleic acid? 

Methods: We used a search strategy to compare studies of nanomedicine systems aimed at eye diseases where the size of the nanoparticles and the efficiency of encapsulation of genetic material are reported based on the criteria of Preferred Reporting Items for Systematic Reviews (PRISMA ScR 2020 guidelines). 

Results: Out of the initial 5932, 169 studies met the inclusion criteria and were included to form the basis of the analysis. Nanoparticles reported are composed mainly of PEG-modified lipids, cholesterol and cationic lipids, that in combination with messenger or interference RNA, allows the formulation of a nanoparticle with an encapsulation efficiency greater than 95%. The diseases treated mainly focus on conditions related to the retina and cornea. Certain characteristics of nanoparticles increase encapsulation efficiency, such as the size of the nanoparticle and the charge of the outer layer of the nanoparticle, so it is essential to determine and further study the optimal characteristics to achieve an effective treatment. Although nucleic acid-loaded lipid nanoparticles are a promising treatment alternative, it still has some limitations.

Background: Polymers used to obtain hydrogels containing mesenchymal stem cells have been the subject of study within the scientific community due to their great potential for differentiation into different cell lineages and their capacity for immunomodulation. These materials can be highly effective in the immunosuppression process in order to favor the regeneration of bone tissue when it has suffered some structural damage. The composition of hydrogels is too heterogeneous in recent research and it is observed that the polymers have an influence on immunomodulation, which is evaluated by genetic expression and proliferation of immune cells; Therefore, the following research question has been raised: How do the polymers present in hydrogels, in conjunction with mesenchymal stem cells, act to modulate the immune response and affect gene expression? 

Methods: Systematic review was carried out following the guidelines established by Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA ScR 2020), with the aim of determining the relationship between polymers and mesenchymal stem cells to attenuate or increase the immune response (measured by gene expression) when osteogenesis is targeted. Results: Out of the initial 239, 184 studies met the inclusion criteria and were included to form the basis of the analysis. The results demonstrate how the composition of the hydrogel (based on polymers), added with mesenchymal stem cells have the ability to be a support and medium for the regeneration of bone tissue is viable by reducing the proinflammatory factors that are an obstacle to achieving it. Hydrogel compositions comprise the polymers PEGDA, CMC + PEGDA, CS, and PLGA 

Conclusion: When a hydrogel loaded with mesenchymal stem cells derived bone marrow and differentiated to the osteogenic lineage is used, they act as a team to reach the site of the injury and promote an anti-inflammatory environment due to the inhibition of immune cells (lymphocytes and M1 macrophages ) and polarization of M2 macrophages, which are responsible for releasing cytokines and growth factors that decrease inflammation.