Biocorrosion and Cytotoxicity Studies on Biodegradable Mg-Based Multicomponent Alloys

Magnesium-based multicomponent alloys with different compositions, namely Mg60Al20Zn5Cu10Mn5 (Mg60 alloy), Mg70Al15Zn5Cu5Mn5 (Mg70 alloy), and Mg80Al5Cu5Mn5Zn5 (Mg 80) alloys, were prepared using the disintegrated melt deposition technique. The DMD technique is a distinctive method that merges the benefits from gravity die casting and spray forming. This approach facilitates high solidification rates, process yields, and reduced metal wastage, resulting in materials with a fine microstructure and minimal porosity. Their potential as biodegradable materials was assessed through corrosion in different simulated body fluids (SBFs), microstructure, and cytotoxicity tests. It was observed that the Mg60 alloy exhibited low corrosion rates (~× 10−5 mm/year) in all SBF solutions, with a minor amount of corrosive products, and cracks were observed. This can be attributed to the formation of the Mg32(AlZn)49 phase and to its stability due to Mg(OH)2 film, leading to excellent corrosion resistance when compared to the Mg70 and M80 alloys. Conversely, the Mg80 alloy exhibited high corrosion rates, along with more surface degradation and cracks, due to active intermetallic phases, such as Al6Mn, Al2CuMg, and Al2Cu phases. The order of corrosion resistance for the Mg alloy was found to be ASS > HBSS > ABP > PBS. Further, in vitro cytotoxicity studies were carried out using MDA-MB-231 tumor cells. By comparing all three alloys, in terms of proliferation and vitality, the Mg80 alloy emerged as a promising material for implants, with potential antitumor activity

Homogeneous poly (L-lactic acid)/chitosan blended films

This work reports an optimized and simple methodology for the preparation of poly(L-lactic) acid/chitosan (CHT) blends by solvent casting based on the use of a common solvent: hexafluor-2-propanol. Films with different component fractions were successfully prepared and did not show visible phase separation. Such biodegradable films have potential to be used in distinct biomedical and environmental applications. The composition effect on film wettability and morphology was investigated by contact angle measurements and scanning electron microscopy. Swelling measurements were also conducted. The composition effect on their thermal properties was analyzed by differential scanning calorimetry. It was found that crystallization is almost suppressed for CHT fractions above 50%. The film miscibility as a function of their composition was evaluated by optical microscopy and Fourier transform infrared spectroscopy imaging. These results evidenced the good miscibility at the microscopic level of the blends. The viscoelastic behavior of the developed films was also studied for the first time by dynamical mechanical analysis (DMA) in an unconventional way: their mechanical properties were measured while they were immersed in gradient compositions of water/ethanol mixtures. This allowed to analyze the glass transition dynamics of the CHT fraction, which would not be possible with conventional DMA tests. DMA temperature scans were also conducted.The authors acknowledge the financial support to the Portuguese Foundation for Science and Technology (FCT), through funding from the SupraRelax project (PTDC/FIS/115048/2009). The authors also acknowledge the help of Rogerio Pirraco in the optical microscopy experiments

Genomic analysis unveils genome degradation events and gene flux in the emergence and persistence of S. Paratyphi A lineages.

Acknowledgements: We thank Prof. Nicholas Grassly, Imperial College London, for assistance with study design and research proposal development. We gratefully acknowledge Dr. Arif M. Tanmoy, Dr. Senjuti Saha and Dr. Yogesh Hooda (CHRF, Dhaka, Bangladesh) for help with the genotyping analysis. We acknowledge Dr. Duncan Steele, Ms. Megan Carey & Dr. Supriya Kumar, Bill & Melinda Gates Foundation for their technical support throughout the study on behalf of SEFI consortium. We thank all the lab members involved in SEFI reference lab activities, especially Dr. Anushree Amladi, Ms. Baby Abirami S, Ms. Dhanabhagyam K, Ms. Beebi E, Ms. Suganya S, Ms. Udaya and Mr. Ayyanraj N, CMC Vellore implicated in phenotypic testing and stock culture maintenance. We would also like to thank all the members of SEFI consortium, Wellcome Trust Research Laboratory, CMC Vellore and core sequencing teams at the Wellcome Trust Sanger Institute for their contribution to genome sequencing. The authors thank Ms Catherine Trueman (Clinical Pharmacist, CMC Vellore) for helping with language editing.Paratyphoid fever caused by S. Paratyphi A is endemic in parts of South Asia and Southeast Asia. The proportion of enteric fever cases caused by S. Paratyphi A has substantially increased, yet only limited data is available on the population structure and genetic diversity of this serovar. We examined the phylogenetic distribution and evolutionary trajectory of S. Paratyphi A isolates collected as part of the Indian enteric fever surveillance study "Surveillance of Enteric Fever in India (SEFI)." In the study period (2017-2020), S. Paratyphi A comprised 17.6% (441/2503) of total enteric fever cases in India, with the isolates highly susceptible to all the major antibiotics used for treatment except fluoroquinolones. Phylogenetic analysis clustered the global S. Paratyphi A collection into seven lineages (A-G), and the present study isolates were distributed in lineages A, C and F. Our analysis highlights that the genome degradation events and gene acquisitions or losses are key molecular events in the evolution of new S. Paratyphi A lineages/sub-lineages. A total of 10 hypothetically disrupted coding sequences (HDCS) or pseudogenes-forming mutations possibly associated with the emergence of lineages were identified. The pan-genome analysis identified the insertion of P2/PSP3 phage and acquisition of IncX1 plasmid during the selection in 2.3.2/2.3.3 and 1.2.2 genotypes, respectively. We have identified six characteristic missense mutations associated with lipopolysaccharide (LPS) biosynthesis genes of S. Paratyphi A, however, these mutations confer only a low structural impact and possibly have minimal impact on vaccine effectiveness. Since S. Paratyphi A is human-restricted, high levels of genetic drift are not expected unless these bacteria transmit to naive hosts. However, public-health investigation and monitoring by means of genomic surveillance would be constantly needed to avoid S. Paratyphi A serovar becoming a public health threat similar to the S. Typhi of today

List of functional gene inactivation mutations identified between phylogenetic lineages.

List of functional gene inactivation mutations identified between phylogenetic lineages.</p