Complete genome sequence of Schaalia odontolytica isolated from subgingival biofilm.

OBJECTIVE: Recent advancements in genome-based taxonomic classification propose the reclassification of certain Actinomyces species into new genera, including Schaalia. Schaalia odontolytica, the type species within this genus, is frequently found in the human oral cavity and has been associated with actinomycotic lesions. Currently, only two complete genomes of S. odontolytica strains have been reported. Recognizing the limited research on subspecies-level variation of S. odontolytica, we conducted genome sequencing of strain KHUD_008, isolated from a Korean periodontitis patient's subgingival biofilm. Additionally, we performed a comparative genome analysis using previously sequenced genomes of strain XH001 and strain FDAARGOS_732, both derived from the human oral cavity. DATA DESCRIPTION: Pacific Biosciences Sequel II sequencing generated 15,904 and 76,557 raw sequencing sub-reads, which were integrated to assemble the de novo genome using the Microbial Genome Analysis pipeline in the Single-Molecule Real-Time Analysis. The genome assembly completeness, assessed by Benchmarking Universal Single-Copy Orthologs, reached 99.2%. The genome is 2,389,595 bp with a GC content of 66.37%, and contains 2,002 protein-coding genes, 9 rRNAs, and 48 tRNA. Comparative analysis with two previously sequenced strains revealed many strain-specific genes in KHUD_008, primarily related to envelope biogenesis and replication/recombination/repair processes.

Draft genome sequence of Limosilactobacillus fermentum isolated from subgingival biofilm.

Limosilactobacillus fermentum is generally considered beneficial for vaginal and digestive health. However, strains isolated from the oral cavity, especially from periodontitis lesions, have not been thoroughly studied. Here, we report the draft genome sequence of strain KHUD_007 isolated from the subgingival biofilm of a Korean patient with periodontitis.

Single-cell RNA sequencing reveals heterogeneity of adipose tissue-derived mesenchymal stem cells under chondrogenic induction.

This study investigated how adipose tissue-derived mesenchymal stem cells (AT-MSCs) respond to chondrogenic induction using droplet-based single-cell RNA sequencing (scRNA-seq). We analyzed 37,219 high-quality transcripts from control cells and cells induced for 1 week (1W) and 2 weeks (2W). Four distinct cell clusters (0-3), undetectable by bulk analysis, exhibited varying proportions. Cluster 1 dominated in control and 1W cells, whereas cluster 3, 2, and 0 exclusively dominated in control, 1W, and 2W cells, respectively. Furthermore, heterogeneous chondrogenic markers expression within clusters emerged. Gene ontology (GO) enrichment analysis of differentially expressed genes unveiled cluster-specific variations in key biological processes (BP): (1) Cluster 1 exhibited upregulation of GO-BP terms related to ribosome biogenesis and translational control, crucial for maintaining stem cell properties and homeostasis; (2) Additionally, cluster 1 showed upregulation of GO-BP terms associated with mitochondrial oxidative metabolism; (3) Cluster 3 displayed upregulation of GO-BP terms related to cell proliferation; (4) Clusters 0 and 2 demonstrated similar upregulation of GO-BP terms linked to collagen fibril organization and supramolecular fiber organization. However, only cluster 0 showed a significant decrease in GO-BP terms related to ribosome production, implying a potential correlation between ribosome regulation and the differentiation stages of AT-MSCs. Overall, our findings highlight heterogeneous cell clusters with varying balances between proliferation and differentiation before and after chondrogenic stimulation. This provides enhanced insights into the single-cell dynamics of AT-MCSs during chondrogenic differentiation.

Genomic and phenotypic comparison of Prevotella intermedia strains possessing different virulence in vivo.

Prevotella intermedia readily colonizes healthy dental biofilm and is associated with periodontal diseases. The viscous exopolysaccharide (EPS)-producing capability is known as a major virulence factor of P. intermedia 17 (Pi17). However, the inter-strain difference in P. intermedia regarding virulence-associated phenotype is not well studied. We compared in vivo virulence and whole genome sequences using five wild-type strains: ATCC 49046 (Pi49046), ATCC 15032 (Pi15032), ATCC 15033 (Pi15033), ATCC 25611 (Pi25611), and Pi17. Non-EPS producing Pi25611 was the least virulent in insect and mammalian models. Unexpectedly, Pi49046 did not produce viscous EPS but was the most virulent, followed by Pi17. Genomes of the five strains were quite similar but revealed subtle differences such as copy number variations and single nucleotide polymorphisms. Variations between strains were found in genes encoding glycosyltransferases and genes involved in the acquisition of carbohydrates and iron/haem. Based on these genetic variations, further analyses were performed. Phylogenetic and structural analyses discovered phosphoglycosyltransferases of Pi49046 and Pi17 have evolved to contain additional loops that may confer substrate specificity. Pi17, Pi15032, and Pi15033 displayed increased growth by various carbohydrates. Meanwhile, Pi49046 exhibited the highest activities for haemolysis and haem accumulation, as well as co-aggregation with Porphyromonas gingivalis harbouring fimA type II, which is more tied to periodontitis than other fimA types. Collectively, subtle genetic differences related to glycosylation and acquisition of carbohydrates and iron/haem may contribute to the diversity of virulence and phenotypic traits among P. intermedia strains. These variations may also reflect versatile strategies for within-host adaptation of P. intermedia.

Development of an Analytical Method for Detection of Anesthetics and Sedatives in Fish.

BACKGROUND: Anesthetics and sedatives are frequently used to prevent abrasions caused by stress and to facilitate fish management. However, drug residues may persist and cause changes in fish conditions and induce side effects. In addition, drugs that are not permitted for use in edible fish are sometimes potentially used in fish. The drugs can also be found in wastewater and are likely to be detected in fish. OBJECTIVE: The purpose of this study was to establish a quantitative analytical method for 10 anesthetic and sedative (azaperone, chlorpromazine, diazepam, estazolam, haloperidol, nitrazepam, nordiazepam, oxazepam, perphenazine, and temazepam) residues in fish sold in Korean markets. METHOD: Shrimp, flounder, and eel samples were selected as matrices. Acetonitrile (ACN) containing 0.1% formic acid was selected as an extraction solvent for shrimp and 100% ACN for flounder and eel. The QuEChERS method with C18 and primary secondary amine (PSA) was used as the extraction procedure, and the analysis was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: Limit of quantitation, recovery, accuracy, and precision were validated, and satisfactory results were obtained for the drugs. All results applied to the real samples were negative. CONCLUSIONS: An optimal validation method was studied. Since the results for all samples were negative, it is considered that additional studies are needed by increasing the number of drugs. HIGHLIGHTS: The most effective QuEChERS pretreatment method and conditions of LC-MS/MS for the analysis of anesthetics and sedatives in fish were established.

Reverse Actuation of Polyelectrolyte Effect for In Vivo Antifouling.

Zwitterionic polymers have extraordinary properties, that is, significant hydration and the so-called antipolyelectrolyte effect, which make them suitable for biomedical applications. The hydration induces an antifouling effect, and this has been investigated significantly. The antipolyelectrolyte effect refers to the extraordinary ion-responsive behavior of particular polymers that swell and hydrate considerably in physiological solutions. This actuation begins to attract attention to achieve in vivo antifouling that is challenging for general polyelectrolytes. In this study, we established the sophisticated cornerstone of the antipolyelectrolyte effect in detail, including (i) the essential parameters, (ii) experimental verifications, and (iii) effect of improving antifouling performance. First, we find that both osmotic force and charge screening are essential factors. Second, we identify the antipolyelectrolyte effect by visualizing the swelling and hydration dynamics. Finally, we verify that the antifouling performance can be enhanced by exploiting the antipolyelectrolyte effect and report reduction of 85% and 80% in ex and in vivo biofilm formation, respectively.

Supporting free clinic patients' social needs with MSW interns: A pilot study.

Social needs, which are social risk factors including lack of access to stable housing, healthy food, or reliable transportation, are recognized as integral to health. Free clinics tend to serve patients with social needs, yet, few are screened or receive assistance. Lack of personnel, resources, and procedures to identify and assist patients are reasons few free clinics consider social needs. To address this service gap, a midwestern free clinic and neighboring Masters of Social Work (MSW) program established a partnership. A social needs screen was developed and integrated into health care practice. An MSW intern was also embedded as a member of the health care team to provide social needs assistance. A 6-month pilot study was conducted to assess the value of the screen and use of MSW assistance services. Of the 223 patients screened, 66.4% (n = 146) scored positive for social needs. Only four percent (n = 6) of the patients used MSW services. Chi-square analyses reveal significant differences in social needs by age, gender, race, education, and primary language. The findings suggest that the screening and MSW intern services are valuable; however, they further suggest that screening alone may be insufficient to encourage utilization of MSW services.

Further examination of knowledge and interactions in ageism among college students: Value for promoting university activities.

Ageism is recognized as a reason that few students pursue careers in aging. While widely studied, the findings regarding factors that contribute to ageism are mixed. The findings from previous studies are also tempered by methodological issues. To better understand the factors that contribute to ageism among students and guide the development of programming and activities to reduce ageism, a survey study was conducted. The study explores associations between frequency of interactions with older adults, quality of the interactions, and ageism. Students' knowledge of aging is also examined. Using refined measures to assess knowledge of aging and interactions with older adults, the study includes data from 1,040 college students, most of whom are traditional age students (i.e., under the age of 25). Findings from multiple regression analyses document the interplay between frequency and quality of interactions and the role of knowledge on multiple dimensions of ageism. Frequency of interactions with older adults is significantly associated with lower levels of ageism only when the interactions are perceived as favorable. Knowledge of aging is significantly associated with lower levels of ageism. The findings provide valuable information for developing activities to reduce ageism. A new ageism reduction program, which was guided by the study findings and age-friendly university framework, is described. Implications for gerontological education are also discussed.

Validation of the Korean version of the Moral Judgment Scale: A process dissociation approach to moral dilemmas.

Conway and Gawronski proposed a scale that independently measures utilitarian and deontological inclinations underlying moral judgments, based on an individual's endorsement of acceptable or unacceptable responses to 10 congruent and 10 incongruent moral dilemmas. This study aimed to develop and standardize the Korean version of this scale and examine the psychometric characteristics of various indexes extracted from it. The English version was translated and back-translated by two independent bilinguals. Inconsistencies between the backward translated version and the original version were resolved by consultation with an independent psychologist. Using an online survey, Korean adults aged 18 years or older were asked to read 20 dilemmas in the Korean version and indicate whether the action undertaken in each dilemma was acceptable, the probability that they would undertake the action themselves, and their level of tension and happiness. A total of 469 adults participated. Participants additionally answered questions that assessed utilitarianism and their level of antisocial personality disorder. Analysis showed that it was appropriate to use 20 dilemmas (10 incongruent and 10 congruent) in Korean adults but psychometric characteristics were different from those of the original English version. The correlation of probability that utilitarianism would drive responses (KU) and the probability that deontology would drive the responses (KD) was -.23 (p < .001). KU showed a significant correlation with utilitarianism (.18, p < .001) and a near-zero correlation with antisocial personality disorder. KD showed a correlation of -.27 (p < .001) with utilitarianism and a correlation of -.13 (p < .01) with antisocial personality disorder. A previous study that proposed that utilitarian and deontological inclinations are independent in moral judgment found a near-zero correlation between U and D, which was different from the result of the present study. Additionally, the limitations and implications of this study are discussed.

A novel retentive type of dental implant prosthesis: marginal fitness of the cementless double crown type implant prosthesis evaluated by bacterial penetration and viability.

PURPOSE: This study aims to compare the marginal fitness of two types of implant-supported fixed dental prosthesis, i.e., cementless fixation (CL.F) system and cement-retained type. MATERIALS AND METHODS: In each group, ten specimens were assessed. Each specimen comprised implant lab analog, titanium abutment fabricated with a 2-degree tapered axial wall, and zirconia crown. The crown of the CL.F system was retained by frictional force between abutment and relined composite resin. In the cement-retained type, zinc oxide eugenol cement was used to set crown and abutment. All specimens were sterilized with ethylene oxide, immersed in Prevotella intermedia culture in a 50 mL tube, and incubated with rotation. After 48 h, the specimens were washed thoroughly before separating the crown and abutment. The bacteria that penetrated into the crown-abutment interface were collected by washing with 500 µL of sterile saline. The bacterial cell number was quantified using the agar plate count technique. The BacTiter-Glo Microbial Cell Viability Assay Kit was used to measure bacterial adenosine triphosphate (ATP)-bioluminescence, which reflects the bacterial viability. The t-test was performed, and the significance level was set at 5%. RESULTS: The number of penetrating bacterial cells assessed by colony-forming units was approximately 33% lower in the CL.F system than in the cement-retained type (P<.05). ATP-bioluminescence was approximately 41% lower in the CL.F system than in the cement-retained type (P<.05). CONCLUSION: The CL.F system is more resistant to bacterial penetration into the abutment-crown interface than the cement-retained type, thereby indicating a precise marginal fit.

Pulsed Electrical Stimulation Enhances Body Fluid Transport for Collagen Biomineralization.

Mechanical loads from physiologic activities such as walking and running generate bioelectricity in bones. By mimicking bioelectricity, external electrical stimulations have also been used therapeutically to stimulate bone-forming cells and, thus, to promote bone regeneration. However, little is known about the physicochemical mechanism(s) by which electrical stimulations drives calcium phosphate mineralization of collagen. Here, we showed that, during in vitro collagen mineralization in the absence of cells, application of pulsed electrical stimulation significantly enhanced the transport of ionic body fluid components through a micrometer-scale channel (∼100-200 µm gap space between the inner surfaces of tube-like collagen scaffolds and a cathode placed inside the collagen scaffolds). The enhanced transport of ionic precursors increased diffusion of the charged precursors from the channel to the inner collagen surface, where bone mineralization was otherwise restricted. The results indicate that pulsed electrical signals can locally accelerate the nucleation of calcium phosphate nanocrystals in or on collagen, allowing us to better control the spatial distribution of the nanocrystals at the microscale. The findings from this study provide insights into the utilization of electrical stimulation for applications such as facilitating bone-fracture healing and designing better bone-specific biomaterials.

Concentrations of THC, CBD, and CBN in commercial hemp seeds and hempseed oil sold in Korea.

Hemp seeds and hempseed oil are marketed on- and off-line as health foods and cosmetics and have been reported to have high nutrient contents. However, because of the various side effects of cannabinoids, especially △9-tetrahydrocannabinol (THC), many countries regulate upper limits for THC in products, which creates the need for analytical techniques capable of measuring THC, cannabidiol (CBD), and cannabinol (CBN) levels in commercial hemp seeds and hempseed oil. In the present study, hemp seed and hempseed oil extracts obtained by methanol extraction, were analyzed by gas chromatography-mass spectrometry (GC/MS). Validation of the technique used was performed using calibration curves and by determining LODs, LOQs, specificities, selectivities, and intra- and inter-day precision and accuracies. In addition, matrix effects, process efficiencies, recoveries, and sample stabilities were investigated. In hemp seeds, as determined using the fully optimized method THC concentrations ranged from 0.06 to 5.91 µg/g, CBD concentrations from 0.32 to 25.55 µg/g, and CBN concentrations from 0.01 to 1.50 µg/g; CBN/THC ratios ranged from 0.1 to 1.60, and CBD/THC ratios from 0.11 to 62.56. Furthermore, the (THC + CBN)/CBD ratio of most hemp seed samples was less than one. In hempseed oil, THC concentrations ranged from 0.3 to 19.73 µg/mL, CBD concentrations from 6.66 to 63.40 µg/mL, CBN concentrations from 0.11 to 2.31 µg/mL, CBN/THC ratios from 0.12 to 0.42, and CBD/THC ratios from 3.21 to 22.50. Furthermore, (THC + CBN)/CBD ratios in all hempseed oil samples were less than one. The optimized methanol extraction-GC/MS technique was found to be satisfactory for determining THC, CBD, and CBN concentrations in hemp seeds and hempseed oil.

The Role of Exosomes in Bronchoalveloar Lavage from Patients with Acute Respiratory Distress Syndrome.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is a life-threatening condition caused by pulmonary and extrapulmonary insults. Exosomes are considered a major cell-to-cell communicator and immune modulator. However, their role in ARDS remains unclear. In this study, we investigated whether exosomes could be a potential biomarker of ARDS. METHODS: We isolated exosomes from bronchoalveolar lavage (BAL) of patients with ARDS. The correlation between the level of exosomes with clinical data, including etiology, oxygenation, and 28-day mortality was analyzed. Enzyme-linked immune sorbent assays and western blotting were carried out to characterize BAL exosomes. Immune modulating response of exosomes was investigated by in vitro examination. RESULTS: From 158 patients, we isolated mean 1568.9 µg/mL BAL exosomes, which presented a negative correlation with the PaO2/FiO2 ratio. The level of exosomes did not correlate with 28-day mortality but was elevated in the infectious etiology of ARDS. The exosomes have cargo proteins associated with apoptosis, necroptosis, and autophagy. An in vitro stimulation study revealed that BAL exosomes could induce the production of proinflammatory cytokines and chemokines, but those from patients with ARDS suppressed the production of vascular endothelial growth factor. CONCLUSIONS: In ARDS, exosomes are released in alveolar space, and the level is correlated with the etiology of ARDS. BAL exosomes could play an immune-modulating role by controlling the production of cytokines.

The relation between temperament and anger response among prisoners: comparison of Reinforcement Sensitivity Theory and the Psychobiological Model of temperament and character.

This study investigates the relation between temperament and anger response among prisoners, and compares temperament as proposed by Reinforcement Sensitivity Theory and the Psychobiological Model of Temperament and Character. We asked 210 prisoners to respond to Korean standardized questionnaires, with items of the Behavioral Inhibition System/Behavioral Approach System (BAS/BIS), and the items of Temperament and character inventory (TCI). Based on the Novaco Anger Scale, prisoners' anger responses were rated as those of direct, indirect, verbal, or impulsive. Three factors of the BAS and BIS all demonstrated significantly positive correlations, while reward dependence and novelty-seeking from the TCI showed a correlation nearing 0. Also, higher harm avoidance of TCI was associated with lower reward dependence, lower level of persistence, and higher level of novelty-seeking of TCI. Regression analyses showed that impulsive anger reaction was significantly explained by novelty-seeking of TCI and BIS; verbal aggression by fun-seeking of BAS and novelty-seeking of TCI; physical confrontation by novelty-seeking of TCI and fun-seeking of BAS; and indirect expression by novelty-seeking, harm avoidance, and persistence of TCI and fun-seeking of BAS.

Effects of Sodium Tripolyphosphate on Oral Commensal and Pathogenic Bacteria.

Polyphosphate (polyP) is a food additive with antimicrobial activity. Here we evaluated the effects of sodium tripolyphosphate (polyP3, Na5P3O10) on four major oral bacterial species, in both single- and mixed-culture. PolyP3 inhibited three opportunistic pathogenic species: Fusobacterium nucleatum, Prevotella intermedia, and Porphyromonas gingivalis. On the contrary, a commensal bacterium Streptococcus gordonii was relatively less susceptible to polyP3 than the pathogens. When all bacterial species were co-cultured, polyP3 (≥ 0.09%) significantly reduced their total growth and biofilm formation, among which the three pathogenic bacteria were selectively inhibited. Collectively, polyP3 may be an alternative antibacterial agent to control oral pathogenic bacteria.Polyphosphate (polyP) is a food additive with antimicrobial activity. Here we evaluated the effects of sodium tripolyphosphate (polyP3, Na5P3O10) on four major oral bacterial species, in both single- and mixed-culture. PolyP3 inhibited three opportunistic pathogenic species: Fusobacterium nucleatum, Prevotella intermedia, and Porphyromonas gingivalis. On the contrary, a commensal bacterium Streptococcus gordonii was relatively less susceptible to polyP3 than the pathogens. When all bacterial species were co-cultured, polyP3 (≥ 0.09%) significantly reduced their total growth and biofilm formation, among which the three pathogenic bacteria were selectively inhibited. Collectively, polyP3 may be an alternative antibacterial agent to control oral pathogenic bacteria.

Bacterial indoleacetic acid-induced synthesis of colloidal Ag2O nanocrystals and their biological activities.

The biosynthesis and biological activity of colloidal Ag2O nanocrystals have not been well studied, although they have potential applications in many fields. For the first time, we developed a reducing agent free, cost-effective technique for Ag2O biosynthesis using Xanthomonas sp. P5. The optimal conditions for Ag2O synthesis were 50 °C, pH 8, and 2.5 mM AgNO3. Using these conditions the yield of Ag2O obtained at 10 h was about five times higher than that obtained at 12 h under unoptimized conditions. Ag2O was characterized by FESEM-EDS, TEM, dynamic light scattering, XRD, and UV-Visible spectroscopy. Indoleacetic acid produced by the strain P2 was involved in the synthesis of Ag2O. Ag2O exhibited a broad antimicrobial spectrum against several human pathogens. Furthermore, Ag2O exhibited 1,1-diphenyl-2-picrylhydrazyl (IC50 = 25.1 µg/ml) and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonate (IC50 = 16.8 µg/ml) radical scavenging activities, and inhibited collagenase (IC50 = 27.9 mg/ml). Cytotoxicity of Ag2O was tested in fibroblast cells and found to be non-toxic, demonstrating biocompatibility.

Biological synthesis and characterisation of silver nanoparticles using Pseudomonas geniculata H10 for pharmaceutical activity.

In the present study, silver nanoparticles (SNPs) were synthesised for the first time using Pseudomonas geniculata H10 as reducing and stabilising agents. The synthesis of SNPs was the maximum when the culture supernatant was treated with 2.5 mM AgNO3 at pH 7 and 40°C for 10 h. The SNPs were characterised by field emission scanning electron microscopy-energy-dispersive spectroscopy, transmission electron microscopy, dynamic light scattering, X-ray diffraction and UV-vis spectroscopy. Fourier transform infrared spectroscopy indicated the presence of proteins, suggesting they may have been responsible for the reduction and acted as capping agents. The SNPs displayed 1,1-diphenyl-2-picrylhydrazyl (IC50 = 28.301 µg/ml) and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonate (IC50 = 27.076 µg/ml) radical scavenging activities. The SNPs exhibited a broad antimicrobial spectrum against several human pathogenic Gram-positive and Gram-negative bacteria and Candida albicans. The antimicrobial action of SNPs was due to cell deformation resulting in cytoplasmic leakage and subsequent lysis. The authors' results indicate P. geniculata H10 could be used to produce antimicrobial SNPs in a facile, non-toxic, cost-effective manner, and that these SNPs can be used as effective growth inhibitors in various microorganisms, making them applicable to various biomedical and environmental systems. As far as the authors are aware, this study is the first to describe the potential biomedical applications of SNPs synthesised using P. geniculata.

Effects of Renaming Schizophrenia in Korea: from "Split-Mind Disorder" to "Attunement Disorder".

OBJECTIVE: Korean Neuropsychiatric Association changed the Korean name of schizophrenia from 'Split-mind Disorder' to 'Attunement Disorder' in 2012. This study assessed attitudes towards the renaming of schizophrenia among mental health practitioners (n=440), patients with schizophrenia and their guardians (n=396), and the university students (n=140) using self-administered questionnaires. METHODS: The questionnaire included items related to participants' perception of the renaming of the disease, the nature of informing about the disease to confirm the effect of the name change. RESULTS: It was confirmed the notification rate of disease name by mental health practitioners was increased significantly after the renaming. Among patients and their guardians, 24.9% and 15.0%, respectively, perceived their own or the family member's illness as 'attunement disorder'. CONCLUSION: Patients and their guardians continue to display a low awareness about the name of the disease as 'attunement disorder.' However, mental health practitioners were found to be able to easily use the name 'attunement disorder' as a result of the increased notification rate of the new disease name.

Stereoselective construction of sterically hindered oxaspirocycles via chiral bidentate directing group-mediated C(sp3)-O bond formation.

The systematic investigation of chiral bidentate auxiliaries has resulted in the discovery of a chiral 2,2-dimethyl-1-(pyridin-2-yl)propan-1-amine-derived directing group that enables stereoselective palladium(ii)-catalyzed intramolecular C(sp3)-O bond formation. This new chiral directing group exhibited high reactivity in the activation of methylene C(sp3)-H bonds with excellent levels of stereoselectivity (a diastereomeric ratio of up to 39 : 1), which allowed the construction of a wide range of oxaspirocycles. Mechanistic investigations were also conducted to elucidate the reaction mechanism and understand the origin of the diastereoselectivity. DFT calculations suggest that only modest levels of diastereoselectivity are accomplished at the rate-determining C-H metalation-deprotonation step and the d.r. is further enriched at the reductive elimination step.

Improved biosynthesis of silver nanoparticles using keratinase from Stenotrophomonas maltophilia R13: reaction optimization, structural characterization, and biomedical activity.

In the present study, keratinase from Stenotrophomonas maltophilia R13 was used for the first time as a reducing agent for the eco-friendly synthesis of AgNPs. The keratinase produced by strain R13 was responsible for the reduction of silver ions and the subsequent formation of AgNPs. Maximum AgNP synthesis was achieved using 2 mM AgNO3 at pH 9 and 40 °C. Electron microscopy and dynamic light scattering analysis showed AgNPs were spherical and of average diameter ~ 8.4 nm. X-ray diffraction revealed that AgNPs were crystalline. FTIR indicated AgNPs were stabilized by proteins present in the crude enzyme solution of strain R13. AgNPs exhibited a broad antimicrobial spectrum against several pathogenic microorganisms, and the antimicrobial mechanism appeared to involve structural deformation of cells resulting in membrane leakage and subsequent lysis. AgNPs also displayed 1,1-diphenyl-2-picrylhydrazyl (IC50 = 0.0112 mg/ml), 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonate radical scavenging (IC50 = 0.0243 mg/ml), and anti-collagenase (IC50 = 23.5 mg/ml) activities.