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Over the past few decades, with the development of science and technology, the field of biomedicine has rapidly developed, especially with respect to biomedical materials. Low toxicity and good biocompatibility have always been key targets in the development and application of biomedical materials. As a degradable and environmentally friendly polymer, polylactic acid, also known as polylactide, is favored by researchers and has been used as a commercial material in various studies. Lactic acid, as a synthetic raw material of polylactic acid, can only be obtained by sugar fermentation. Good biocompatibility and biodegradability have led it to be approved by the U.S. Food and Drug Administration (FDA) as a biomedical material. Polylactic acid has good physical properties, and its modification can optimize its properties to a certain extent. Polylactic acid blocks and blends play significant roles in drug delivery, implants, and tissue engineering to great effect. This article describes the synthesis of polylactic acid (PLA) and its raw materials, physical properties, degradation, modification, and applications in the field of biomedicine. It aims to contribute to the important knowledge and development of PLA in biomedical applications.

Background The defining feature of the cerebrospinal fluid (CSF) collected from infants and children with tuberculous meningitis (TBM), derived from an earlier untargeted nuclear magnetic resonance (NMR) metabolomics study, was highly elevated lactic acid. Undetermined was the contribution from host response (L-lactic acid) or of microbial origin (D-lactic acid), which was set out to be determined in this study. Methods In this follow-up study, we used targeted ultra-performance liquid chromatography–electrospray ionization–tandem mass spectrometry (UPLC–ESI–MS/MS) to determine the ratio of the L and D enantiomers of lactic acid in these CSF samples. Results Here we report for the first time that the lactic acid observed in the CSF of confirmed TBM cases was in the L-form and solely a response from the host to the infection, with no contribution from any bacteria. The significance of elevated lactic acid in TBM appears to be that it is a crucial energy substrate, used preferentially over glucose by microglia, and exhibits neuroprotective capabilities. Conclusion These results provide experimental evidence to support our conceptual astrocyte–microglia lactate shuttle model formulated from our previous NMR-based metabolomics study — highlighting the fact that lactic acid plays an important role in neuroinflammatory diseases such as TBM. Furthermore, this study reinforces our belief that the determination of enantiomers of metabolites corresponding to infectious diseases is of critical importance in substantiating the clinical significance of disease markers.

The relaxation of the glass of poly ( l -lactic acid) (PLLA) and its random copolymers with 2 and 4 mol% d -isomer co-units has been analyzed by conventional differential scanning calorimetry. It was found that the presence of up to 4% d -isomer co-units in the PLLA chain has no measurable effect on the glass relaxation kinetics in fully amorphous samples. At ambient temperature, after rapid cooling of the melt at a rate of 50 K/min, to avoid crystallization, the glass relaxation begins after about 10 min and is not finished within 5000 min. The relaxation of the glass is accompanied by a major change of mechanical properties as it was revealed by time-resolved measurements of the micro-indentation hardness and Young’s modulus. During annealing of amorphous PLLA at ambient temperature, the microhardness and Young’s modulus increase by more than 40 and 10%, respectively, within a time period of about one month, and with an equilibrium value not yet achieved even after such a long annealing time. As in case of the enthalpy-relaxation kinetics, both, absolute values and the time evolution of the analyzed mechanical properties are independent on the presence of d -isomer co-units in the PLLA chain within the investigated concentration range.

Batch cultivation of monoculture of Lactobacillus sp. and two-strain mixed culture of Lactobacillus sp. and Lactobacillus amylovorus DSM [20531.sup.T] was carried out with the aim of producing L-(+)- and D-(-)/L-(+)-lactic acid to be implemented in poly(lactic acid) polymer production. Metabolic capacity of two Lactobacillus strains to ferment different carbon sources (glucose, sucrose or soluble starch) during cultivation in MRS medium at 40°C, in a laboratory-scale stirred tank bioreactor was defined. Lactobacillus sp. showed similar affinity towards mono- and disaccharide substrates, which were homofermentatively converted mostly to L-(+)-lactic acid. L. amylovorus DSM [20531.sup.T] has been characterized as a D/L-lactate producer and it is capable of conducting simultaneous saccharification and fermentation. Due to the interaction of Lactobacillus sp. with L. amylovorus DSM [20531.sup.T], starch was hydrolysed and fermented to the mixture of L-(+)- and D-(-)-lactic acid. Modified LuedekingPiret kinetics used for the description of substrate utilization, growth of mono- and mixed cultures and production of lactic acid stereoisomers showed good agreement with experimental data. Key words. monoculture, mixed culture, Lactobacillus sp., batch fermentation, L-(+)- and/or D-(-)-lactic acid, bacteriocin, amensalism, mathematical model

Fermentation of tomato pulp by the bacteriocin-producing lactic acid bacteria (Lactobacillus sakei KTU05-6, Pediococcus acidilactici KTU05-7 and Pediococcus pentosaceus KTU05-8) was applied as a preservation method for the production of tomato products. The changes in L- and D-lactic acid contents during fermentation of different tomato varieties (Ronaldo and Cunero) were analysed. Additionally, the effects of lacto-fermentation on the cis/trans lycopene ratio, b-carotene content, and their relation to colour characteristics of fermented tomato products were investigated. Mass fractions of L- and D-lactic acid in the fermented tomato products varied from (4.25 plus or minus 0.04) to (7.19 plus or minus 0.08) mg per 100 g, and from (4.05 plus or minus 0.05) to (6.34 plus or minus 0.04) mg per 100 g, respectively. Fermentation with P. acidilactici or L. sakei culture resulted in the the decrease of D-lactic acid content by 43.6 and 37.7%, respectively, compared to spontaneous fermentation. Fermentation of tomato with selected lactic acid bacteria resulted in a greater lycopene bioavailability accompanied by an increase in cis-lycopene isomer content.

Poly(lactic acid) (PLA) is an important polymer that is based on renewable biomass resources. Because of environmental issues, more renewable sources for polymers synthesis have been sought for industrial purposes. In this sense, cheaper monomers should be used to facilitate better utilization of less valuable chemicals and therefore granting more sustainable processes. Some points are raised about the need to study the total degradability of any PLA, which may require specific composting conditions (e.g., temperature, type of microorganism, adequate humidity and aerobic environment). Polymerization processes to produce PLA are presented with an emphasis on D,L-lactic acid (or rac-lactide) as the reactant monomer. The syntheses involving homogeneous and heterogeneous catalytic processes to produce poly(D,L-Lactic acid) (PDLLA) are also addressed. Additionally, the production of blends, copolymers, and composites with PDLLA are also presented exemplifying different preparation methods. Some general applications of these materials mostly dedicated to the biomedical area over the last 10–15 years will be pointed out.

Background The concept of “skin boosters” has evolved, marking a shift from traditional uses of hyaluronic acid (HA) fillers primarily for augmenting skin volume to a more diverse application aimed at improving dermal conditions. Restylane Vital and other HA fillers have been repurposed to combat skin aging and wrinkles by delivering HA directly to the dermis. Objectives This review aims to define the term “skin booster” and to discuss the various components that constitute skin boosters. It seeks to provide a comprehensive overview of the different ingredients used in skin boosters, their roles, and their impact on enhancing dermal conditions. Methods A comprehensive review was conducted, focusing on representative skin booster ingredients. The approach involved analyzing the different elements used in skin boosters and their specific roles in enhancing dermal improvement. Results The findings indicate that skin boosters, encompassing a range of ingredients, are effective in improving the condition of the skin's dermis. The review identifies key ingredients in skin boosters and their specific benefits, including hydration, elasticity improvement, and wrinkle reduction. Conclusions Skin boosters represent a significant development in dermatological treatments, offering diverse benefits beyond traditional HA fillers. This review provides valuable insights into the constituents of skin boosters and their effectiveness, aiding readers in making informed decisions about these treatments. The potential of skin boosters in dermatological practice is considerable, warranting further research and application.

ABSTRACT Background Melasma is a chronic, recurrent skin disorder with limited long‐term treatment success using conventional therapies like hydroquinone and laser treatments, which primarily target epidermal components while leaving dermal aspects untreated. Objective To evaluate the efficacy and safety of poly‐d,l lactic acid (PDLLA) subdermal injections for treating moderate melasma. Methods Three female patients (age range: 45–59 years) with Fitzpatrick skin types III and IV received three PDLLA injection sessions at 3‐week intervals. Treatment outcomes were assessed using the Melasma Area and Severity Index (MASI) and patient satisfaction scores at 12‐week follow‐up. Results All patients showed significant MASI score improvements (reduction range: 3.60–6.30 points). Patient satisfaction ratings ranged from 3 to 4 out of 4. Temporary side effects included mild edema and bruising, resolving within 72 h. Conclusions PDLLA subdermal injections showed promising results in melasma treatment, potentially due to its biostimulatory effects on collagen production and dermal remodeling. Further research, including histopathological analysis, is needed to confirm long‐term efficacy and safety, and understand underlying mechanisms.