Antibacterial applications of biologically synthesized Pichia pastoris silver nanoparticles

Objectives

This article highlights the biological synthesis of silver nanoparticles (AgNPs) with their characteristic analysis, and it focuses on the application of synthesized NPs against multidrug resistance (MDR) bacteria. A cytotoxicity study was performed to assess the biocompatibility.

Methods

Silver nanoparticle (AgNPs) formation was confirmed by different characterization methods such as UV-Vis spectrophotometer, Dynamic light scattering (DLS)- Zeta, Fourier transform infrared (FTIR), and Transmission electron microscope (TEM). The antimicrobial activity of the AgNPs was checked against various bacterial strains of Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), and Klebsiella pneumonia (K. pneumonia) by disc diffusion, minimum inhibition concentration test (MIC), and kinetic studies. The cytotoxicity of NPs against the Vero cell line was studied by cytotoxic assay.

Results

The primary analysis of the formation of nanoparticles (NPs) was made by UV-Vis spectrophotometric analysis at 400 nm. At the same time, the efficient capping checked by FTIR shows the presence of a functional group at different wavelengths 3284, 1641,1573,1388,1288, and 1068 cm-1. At the same time, the transmission electron microscopic analysis (TEM) and DLS show that the shape and size of the synthesized NPs possess an average size of around ∼10-30 nm with spherical morphology. Further, the zeta potential confirmed the stability of the NPs. While the yield of NPs formation from silver salt was determined by an online yield calculator with the EDX analysis results. Synthesized NPs showed bactericidal effects against all the selected MDR pathogens with nontoxic effects against mammalian cells.

Conclusion

Our findings indicate the remarkable antimicrobial activity of the biologically synthesized AgNPs, which can be an antimicrobial agent against multi-drug-resistant bacteria.

Differences in interaction of graphene/graphene oxide with bacterial and mammalian cell membranes

Graphene, a single layer, hexagonally packed two-dimensional carbon sheet is an attractive candidate for diverse applications including antibacterial potential and drug delivery. One of the knowledge gaps in biomedical application of graphene is the interaction of these materials with the cells. To address this, we investigated the interaction between graphene materials (graphene and graphene oxide) and plasma membranes of cells (bacterial and mammalian cells). The interactions of four of the most abundant phospholipids in bacteria and mammalian plasma membranes with graphene materials were studied using density functional theory (DFT) at the atomic level. The calculations showed that the mammalian phospholipids have stronger bonding to each other compared to bacterial phospholipids. When the graphene/graphene oxide sheet is approaching the phospholipid pairs, the bacterial pairs exhibit less repulsive interactions, thereby a more stable system with the sheets was found. We also assembled bacterial and mammalian phospholipids into liposomes. We further observed that the bacterial liposomes and cells let the graphene flakes penetrate the membrane. The differential scanning calorimetry measurements of liposomes revealed that the bacterial liposomes have the lowest heat capacity; this strengthens the theoretical predictions of weaker interaction between the bacterial phospholipids compared to the mammalian phospholipids. We further demonstrated that graphene oxide could be internalized into the mammalian liposomes without disrupting the membrane integrity. The results suggest that the weak bonding among bacteria phospholipids and less repulsive force when graphene materials approach, result in graphene materials interacting differently with the bacteria compared to mammalian cells.

Biomimetic Antibacterial Gelatin Hydrogels with Multifunctional Properties for Biomedical Applications

A facile novel approach of introducing dopamine and [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide via dopamine-triggered in situ synthesis into gelatin hydrogels in the presence of ZnSO4 is presented in this study. Remarkably, the resulting hydrogels showed 99.99 and 100% antibacterial efficiency against Gram-positive and Gram-negative bacteria, respectively, making them the highest performing surfaces in their class. Furthermore, the hydrogels showed adhesive properties, self-healing ability, antifreeze properties, electrical conductivity, fatigue resistance, and mechanical stability from -100 to 80 °C. The added multifunctional performance overcomes several disadvantages of gelatin-based hydrogels such as poor mechanical properties and limited thermostability. Overall, the newly developed hydrogels show significant potential for numerous biomedical applications, such as wearable monitoring sensors and antibacterial coatings.

Polysaccharide-based antibacterial coating technologies

To tackle antimicrobial resistance, a global threat identified by the United Nations, is a common cause of healthcare-associated infections (HAI) and is responsible for significant costs on healthcare systems, a substantial amount of research has been devoted to developing polysaccharide-based strategies that prevent bacterial attachment and biofilm formation on surfaces. Polysaccharides are essential building blocks for life and an abundant renewable resource that have attracted much attention due to their intrinsic remarkable biological potential antibacterial activities. If converted into efficient antibacterial coatings that could be applied to a broad range of surfaces and applications, polysaccharide-based coatings could have a significant potential global impact. However, the ultimate success of polysaccharide-based antibacterial materials will be determined by their potential for use in manufacturing processes that are scalable, versatile, and affordable. Therefore, in this review we focus on recent advances in polysaccharide-based antibacterial coatings from the perspective of fabrication methods. We first provide an overview of strategies for designing polysaccharide-based antimicrobial formulations and methods to assess the antibacterial properties of coatings. Recent advances on manufacturing polysaccharide-based coatings using some of the most common polysaccharides and fabrication methods are then detailed, followed by a critical comparative overview of associated challenges and opportunities for future developments. STATEMENT OF SIGNIFICANCE: Our review presents a timely perspective by being the first review in the field to focus on advances on polysaccharide-based antibacterial coatings from the perspective of fabrication methods along with an overview of strategies for designing polysaccharide-based antimicrobial formulations, methods to assess the antibacterial properties of coatings as well as a critical comparative overview of associated challenges and opportunities for future developments. Meanwhile this work is specifically targeted at an audience focused on featuring critical information and guidelines for developing polysaccharide-based coatings. Including such a complementary work in the journal could lead to further developments on polysaccharide antibacterial applications.

Antibiotic-Loaded Boron Nitride Nanoconjugate with Strong Performance against Planktonic Bacteria and Biofilms

Protecting surfaces from biofilm formation presents a significant challenge in the biomedical field. The utilization of antimicrobial component-conjugated nanoparticles is becoming an attractive strategy against infectious biofilms. Boron nitride (BN) nanomaterials have a unique biomedical application value due to their excellent biocompatibility. Here, we developed antibiotic-loaded BN nanoconjugates to combat bacterial biofilms. Antibiofilm testing included two types of pathogens, Staphylococcus aureus and Escherichia coli. Gentamicin was loaded on polydopamine-modified BN nanoparticles (GPBN) to construct a nanoconjugate, which was very effective in killing E. coli and S. aureus planktonic cells. GPBN exhibited equally strong capacity for biofilm destruction, tested on preformed biofilms. A 24 h treatment with the nanoconjugate reduced cell viability by more than 90%. Our results suggest that GPBN adheres to the surface of the biofilm, penetrates inside the biofilm matrix, and finally deactivates the cells. Interestingly, the GPBN coatings also strongly inhibited the formation of bacterial biofilms. Based on these results, we suggest that GPBN could serve as an effective means for treating biofilm-associated infections and as coatings for biofilm prevention.

Polymyxin B complexation enhances the antimicrobial potential of graphene oxide

Introduction

The antibacterial activity of graphene oxide (GO) has been widely explored and tested against various pathogenic bacterial strains. Although antimicrobial activity of GO against planktonic bacterial cells was demonstrated, its bacteriostatic and bactericidal effect alone is not sufficient to damage sedentary and well protected bacterial cells inside biofilms. Thus, to be utilized as an effective antibacterial agent, it is necessary to improve the antibacterial activity of GO either by integration with other nanomaterials or by attachment of antimicrobial agents. In this study, antimicrobial peptide polymyxin B (PMB) was adsorbed onto the surface of pristine GO and GO functionalized with triethylene glycol.

Methods

The antibacterial effects of the resulting materials were examined by evaluating minimum inhibitory concentration, minimum bactericidal concentration, time kill assay, live/dead viability staining and scanning electron microscopy.

Results and discussion

PMB adsorption significantly enhanced the bacteriostatic and bactericidal activity of GO against both planktonic cells and bacterial cells in biofilms. Furthermore, the coatings of PMB-adsorbed GO applied to catheter tubes strongly mitigated biofilm formation, by preventing bacterial adhesion and killing the bacterial cells that managed to attach. The presented results suggest that antibacterial peptide absorption can significantly enhance the antibacterial activity of GO and the resulting material can be effectively used not only against planktonic bacteria but also against infectious biofilms.

Automated Prediction of Bacterial Exclusion Areas on SEM Images of Graphene-Polymer Composites

To counter the rising threat of bacterial infections in the post-antibiotic age, intensive efforts are invested in engineering new materials with antibacterial properties. The key bottleneck in this initiative is the speed of evaluation of the antibacterial potential of new materials. To overcome this, we developed an automated pipeline for the prediction of antibacterial potential based on scanning electron microscopy images of engineered surfaces. We developed polymer composites containing graphite-oriented nanoplatelets (GNPs). The key property that the algorithm needs to consider is the density of sharp exposed edges of GNPs that kill bacteria on contact. The surface area of these sharp exposed edges of GNPs, accessible to bacteria, needs to be inferior to the diameter of a typical bacterial cell. To test this assumption, we prepared several composites with variable distribution of exposed edges of GNP. For each of them, the percentage of bacterial exclusion area was predicted by our algorithm and validated experimentally by measuring the loss of viability of the opportunistic pathogen Staphylococcus epidermidis. We observed a remarkable linear correlation between predicted bacterial exclusion area and measured loss of viability (R² = 0.95). The algorithm parameters we used are not generally applicable to any antibacterial surface. For each surface, key mechanistic parameters must be defined for successful prediction.

Silver Nanoparticles: Bactericidal and Mechanistic Approach against Drug Resistant Pathogens

This review highlights the different modes of synthesizing silver nanoparticles (AgNPs) from their elemental state to particle format and their mechanism of action against multidrug-resistant and biofilm-forming bacterial pathogens. Various studies have demonstrated that the AgNPs cause oxidative stress, protein dysfunction, membrane disruption, and DNA damage in bacteria, ultimately leading to bacterial death. AgNPs have also been found to alter the adhesion of bacterial cells to prevent biofilm formation. The benefits of using AgNPs in medicine are, to some extent, counter-weighted by their toxic effect on humans and the environment. In this review, we have compiled recent studies demonstrating the antibacterial activity of AgNPs, and we are discussing the known mechanisms of action of AgNPs against bacterial pathogens. Ongoing clinical trials involving AgNPs are briefly presented. A particular focus is placed on the mechanism of interaction of AgNPs with bacterial biofilms, which are a significant pathogenicity determinant. A brief overview of the use of AgNPs in other medical applications (e.g., diagnostics, promotion of wound healing) and the non-medical sectors is presented. Finally, current drawbacks and limitations of AgNPs use in medicine are discussed, and perspectives for the improved future use of functionalized AgNPs in medical applications are presented.

Ginsenoside Rg3 Reduces the Toxicity of Graphene Oxide Used for pH-Responsive Delivery of Doxorubicin to Liver and Breast Cancer Cells

Doxorubicin (DOX) is extensively used in chemotherapy, but it has serious side effects and is inefficient against some cancers, e.g., hepatocarcinoma. To ameliorate the delivery of DOX and reduce its side effects, we designed a pH-responsive delivery system based on graphene oxide (GO) that is capable of a targeted drug release in the acidic tumor microenvironment. GO itself disrupted glutathione biosynthesis and induced reactive oxygen species (ROS) accumulation in human cells. It induced IL17-directed JAK-STAT signaling and VEGF gene expression, leading to increased cell proliferation as an unwanted effect. To counter this, GO was conjugated with the antioxidant, ginsenoside Rg3, prior to loading with DOX. The conjugation of Rg3 to GO significantly reduced the toxicity of the GO carrier by abolishing ROS production. Furthermore, treatment of cells with GO-Rg3 did not induce IL17-directed JAK-STAT signaling and VEGF gene expression-nor cell proliferation-suggesting GO-Rg3 as a promising drug carrier. The anticancer activity of GO-Rg3-DOX conjugates was investigated against Huh7 hepatocarcinoma and MDA-MB-231 breast cancer cells. GO-Rg3-DOX conjugates significantly reduced cancer cell viability, primarily via downregulation of transcription regulatory genes and upregulation of apoptosis genes. GO-Rg3 is an effective, biocompatible, and pH responsive DOX carrier with potential to improve chemotherapy-at least against liver and breast cancers.

Economic burden of limited English proficiency: A prevalence-based cost of illness study of its direct, indirect, and intangible costs

Aims

The primary objective of the present study was to evaluate the economic burden of limited English proficiency (LEP) by estimating its direct, indirect, and intangible costs. A secondary objective was to assess the impact of variables on the economic burden.

Design and Setting

A cross-sectional single-arm descriptive study conducted in a learning disability clinic in a public medical college in Mumbai.

Subjects and Methods

The study cases (aged ≥8 years and ≤18 years) were recruited by non-probability sampling. A structured questionnaire was used to interview the parent to collect data related to direct and indirect costs. Intangible cost data were collected by documenting the willingness-to-pay value using the contingent valuation technique.

Statistical Analysis Used

A multivariate regression model was used to assess the impact of predictor variables on the costs.

Results

The direct, indirect, and intangible costs due to LEP were Indian Rupees (INR) 826,736, 3,828,220, and 1,906,300, respectively. Indirect costs comprised 82.2% of the total costs. Expenditure on tuition and remedial education comprised 39.86% and 14.08% of the indirect and direct costs, respectively. The average annual learning disability clinic costs were INR 2,169,146. The average annual total costs per student were INR 42,102. Higher socioeconomic status was predictive of increased "indirect costs", "total costs", and "intangible costs."

Conclusion

LEP is a cost-intensive condition (indirect > intangible > direct costs). Non-medical costs are the costliest component of direct costs. Parental loss of earnings is the costliest component of indirect costs.

Post-tonsillectomy Hemorrhage in Patients Receiving Ketorolac Analgesic

Background Ketorolac, the non-steroidal anti-inflammatory drug, is thought to have less sedation as well as postoperative nausea and vomiting in comparison to opioids, but with higher risk of post-tonsillectomy hemorrhage as reported in some of the literatures. There is no consensus till date in the use of ketorolac in the management of pain following tonsil and adenoid related surgeries. Objective To find out the incidence of hemorrhage following tonsil and adenoid related surgeries in patients receiving ketorolac in postoperative period. Method This is a retrospective chart review of patients undergoing tonsil and adenoid related surgeries who had received ketorolac during April, 2013 to May, 2019 at department of ENT-HNS, Patan Academy of Health Sciences (PAHS), Lalitpur, Nepal. Post-tonsillectomy hemorrhage rate was calculated in pediatric and adult patients. Result During the study period, 103 patients (male - 50 and female - 53) received ketorolac in postoperative period. Tonsillectomy and adenotonsillectomy were performed in 71and 32 patients respectively. Forty-five patients were < 18 years whereas 58 were ≥ 18 years. Most common indication for surgery was recurrent tonsillitis (66/103) followed by adenotonsillar hypertrophy (31/103). Post-tonsillectomy hemorrhage was observed in 15 patients; among them, four out 45 were < 18 years and 11 out of 58 ≥ 18 years. All five patients out of 15, who required surgical intervention for post-tonsillectomy hemorrhage, were ≥ 18 years and were operated for recurrent tonsillitis. Rest of the patients (10/15) were managed conservatively. None of the patients required blood transfusion. Conclusion Ketorolac is not associated with increased risk of post-tonsillectomy hemorrhage in children and can safely be administered. Whereas in adults, recurrent tonsillitis being the most common indication for tonsillectomy, it should be used cautiously.

Antimicrobial Activity of Graphene Oxide Contributes to Alteration of Key Stress-Related and Membrane Bound Proteins

Introduction

Antibacterial activity of graphene oxide (GO) has been extensively studied, wherein penetration of the bacterial cell membrane and oxidative stress are considered to play a major role in the bactericidal activity of GO. However, the specific mechanism responsible for the antibacterial activity of GO remains largely unknown. Hence, the goal of this study was to explore the mode of action of GO, via an in-depth proteomic analysis of the targeted bacteria.

Methods

Staphylococcus aureus was grown in the presence of GO and samples were collected at different growth phases to examine the cell viability and to analyze the changes in protein expression. Antimicrobial efficiency of GO was tested by assessing bacterial viability, live/dead staining and scanning electron microscopy. The intracellular reactive oxygen species (ROS) induced by GO treatment were examined by fluorescence microscopy. Label-free quantitative proteomics analysis was performed to examine the differentially regulated proteins in S. aureus after GO treatment.

Results

GO treatment was observed to reduce S. aureus viability, from 50 ± 17% after 4 h, to 93 ± 2% after 24 h. The live/dead staining confirmed this progressive antimicrobial effect of GO. SEM images revealed the wrapping of bacterial cells and their morphological disruption by means of pore formation due to GO insertion. GO treatment was observed to generate intracellular ROS, correlating to the loss of cell viability. The proteomics analysis revealed alteration in the expression of cell membrane, oxidative stress response, general stress response, and virulence-associated proteins in GO-treated bacterial cells. The time-dependent bactericidal activity of GO correlated with a higher number of differentially regulated proteins involved in the above.-mentioned processes.

Conclusion

The obtained results suggest that the time-dependent bactericidal effect of GO is attributed to its wrapping/trapping ability, ROS production and due to physical disruption of the cell membrane.

Cellular and subcellular interactions of graphene-based materials with cancerous and non-cancerous cells

Despite significant advances in early detection and personalized treatment, cancer is still among the leading causes of death globally. One of the possible anticancer approaches that is presently receiving a lot of attention is the development of nanocarriers capable of specific and efficient delivery of anticancer drugs. Graphene-based materials are promising nanocarriers in this respect, due to their high drug loading capacity and biocompatibility. In this review, we present an overview on the interactions of graphene-based materials with normal mammalian cells at the molecular level as well as cellular and subcellular levels, including plasma membrane, cytoskeleton, and membrane-bound organelles such as lysosomes, mitochondria, nucleus, endoplasmic reticulum, and peroxisome. In parallel, we assemble the knowledge about the interactions of graphene-based materials with cancerous cells, that are considered as the potential applications of these materials for cancer therapy including metastasis treatment, targeted drug delivery, and differentiation to non-cancer stem cells. We highlight the influence of key parameters, such as the size and surface chemistry of graphene-based materials that govern the efficiency of internalization and biocompatibility of these particles in vitro and in vivo. Finally, this review aims to correlate the key parameters of graphene-based nanomaterials specially graphene oxide, such as size and surface modifications, to their interactions with the cancerous and non-cancerous cells for designing and engineering them for bio-applications and especially for therapeutic purposes.

A Road Map toward Field-Effect Transistor Biosensor Technology for Early Stage Cancer Detection

Field effect transistor (FET)-based nanoelectronic biosensor devices provide a viable route for specific and sensitive detection of cancer biomarkers, which can be used for early stage cancer detection, monitoring the progress of the disease, and evaluating the effectiveness of therapies. On the road to implementation of FET-based devices in cancer diagnostics, several key issues need to be addressed: sensitivity, selectivity, operational conditions, anti-interference, reusability, reproducibility, disposability, large-scale production, and economic viability. To address these well-known issues, significant research efforts have been made recently. An overview of these efforts is provided here, highlighting the approaches and strategies presently engaged at each developmental stage, from the design and fabrication of devices to performance evaluation and data analysis. Specifically, this review discusses the multistep fabrication of FETs, choice of bioreceptors for relevant biomarkers, operational conditions, measurement configuration, and outlines strategies to improve the sensing performance and reach the level required for clinical applications. Finally, this review outlines the expected progress to the future generation of FET-based diagnostic devices and discusses their potential for detection of cancer biomarkers as well as biomarkers of other noncommunicable and communicable diseases.

Enriched microbial communities for ammonium and nitrite removal from recirculating aquaculture systems

The aim of this study was the enrichment of high-performance microbial communities in biofilters for removal of ammonium and nitrite from aquaculture water. Ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were enriched from different environmental water samples. The microbial communities with higher ammonium and nitrite removal activity were selected and adapted to different temperatures [9 °C, 15 °C, room temperature (25 °C), and 30 °C]. The expression of genes involved in nitrification including ammonia monooxygenase (AMO) and nitrite oxidoreductase (NXR) were measured in temperature-adapted AOB and NOB microbiomes. The microbial species present in the selected microbiomes were identified via 16s rRNA sequencing. The microbial communities containing Nitrosomonas oligotropha and Nitrobacter winogradskyi showed the highest ammonium and nitrite removal activity at all temperatures used for adaptation. Furthermore, the microbial communities do not contain any pathogenic bacteria. They also exhibited the highest expression of AMO and NXR genes. Using the enriched microbial communities, we achieved a 288% and 181% improvement in ammonium and nitrite removal over the commonly used communities in biofilters at 9 °C, respectively. These results suggest that the selected microbiomes allowed for a significant improvement of water quality in a recirculating aquaculture system (RAS).

Insights into the Mechanism for Vertical Graphene Growth by Plasma-Enhanced Chemical Vapor Deposition

Vertically oriented graphene (VG) has attracted attention for years, but the growth mechanism is still not fully revealed. The electric field may play a role, but the direct evidence and exactly what role it plays remains unclear. Here, we conduct a systematic study and find that in plasma-enhanced chemical vapor deposition, the VG growth preferably occurs at spots where the local field is stronger, for example, at GaN nanowire tips. On almost round-shaped nanoparticles, instead of being perpendicular to the substrate, the VG grows along the field direction, that is, perpendicular to the particles' local surfaces. Even more convincingly, the sheath field is screened to different degrees, and a direct correlation between the field strength and the VG growth is observed. Numerical calculation suggests that during the growth, the field helps accumulate charges on graphene, which eventually changes the cohesive graphene layers into separate three-dimensional VG flakes. Furthermore, the field helps attract charged precursors to places sticking out from the substrate and makes them even sharper and turn into VG. Finally, we demonstrate that the VG-covered nanoparticles are benign to human blood leukocytes and could be considered for drug delivery. Our research may serve as a starting point for further vertical two-dimensional material growth mechanism studies.

Parental-perceived health-related quality of life of school students with borderline intellectual functioning: A cross-sectional questionnaire-based study in Mumbai, Maharashtra, India

Background and Objectives

Students with borderline intellectual functioning ("slow learners") underperform in all school subjects. The primary objective of this study was to evaluate the parental-perceived health-related quality of life (HRQoL) of these students. Its secondary objective was to analyze the impact of sociodemographic variables on their HRQoL.

Settings and Design

Cross-sectional single-arm questionnaire-based study was conducted in the learning disability clinic in a public medical college in Mumbai.

Subjects and Methods

One hundred parents of slow learners aged 8 to 16 years were recruited by non-probability sampling. Their HRQoL scores were measured using the English DISABKIDS chronic generic module parent (proxy) long-version ("DCGM-37-P") instrument.

Statistical Analysis

Multiple regression analysis was carried out for determining the "independent" impact that sociodemographic variables had on a poor facet and total score outcomes.

Results

Clinically significant deficits were detected in 4 facets, namely: small deficit in "social inclusion"; medium deficits in "independence", "emotion", and "social exclusion"; and large deficit in "total score". Multivariate analysis revealed that: (i) being an only child predicted a poor "emotion" and "social exclusion" facet score outcomes (P = 0.039 and P = 0.024, respectively); (ii) being a female predicted a poor "social inclusion" facet score outcome (P = 0.022); and, (iii) studying in a single-gender school predicted a poor "limitation" facet score outcome (P = 0.020).

Conclusions

Parents of slow learners perceive their psychosocial and total HRQoL to be significantly compromised. There is a need to evaluate the HRQoL of slow learners so that optimum rehabilitation can be facilitated.

Graphene-Based Sensor for Detection of Bacterial Pathogens

Microbial colonization to biomedical surfaces and biofilm formation is one of the key challenges in the medical field. Recalcitrant biofilms on such surfaces cause serious infections which are difficult to treat using antimicrobial agents, due to their complex structure. Early detection of microbial colonization and monitoring of biofilm growth could turn the tide by providing timely guidance for treatment or replacement of biomedical devices. Hence, there is a need for sensors, which could generate rapid signals upon bacterial colonization. In this study, we developed a simple prototype sensor based on pristine, non-functionalized graphene. The detection principle is a change in electrical resistance of graphene upon exposure to bacterial cells. Without functionalization with specific receptors, such sensors cannot be expected to be selective to certain bacteria. However, we demonstrated that two different bacterial species can be detected and differentiated by our sensor due to their different growth dynamics, adherence pattern, density of adhered bacteria and microcolonies formation. These distinct behaviors of tested bacteria depicted distinguishable pattern of resistance change, resistance versus gate voltage plot and hysteresis effect. This sensor is simple to fabricate, can easily be miniaturized, and can be effective in cases when precise identification of species is not needed.

Sustained release of usnic acid from graphene coatings ensures long term antibiofilm protection

Protecting surfaces from bacterial colonization and biofilm development is an important challenge for the medical sector, particularly when it comes to biomedical devices and implants that spend longer periods in contact with the human body. A particularly difficult challenge is ensuring long-term protection, which is usually attempted by ensuring sustained release of antibacterial compounds loaded onto various coatings. Graphene have a considerable potential to reversibly interact water insoluble molecules, which makes them promising cargo systems for sustained release of such compounds. In this study, we developed graphene coatings that act as carriers capable of sustained release of usnic acid (UA), and hence enable long-term protection of surfaces against colonization by bacterial pathogens Staphylococcus aureus and Staphylococcus epidermidis. Our coatings exhibited several features that made them particularly effective for antibiofilm protection: (i) UA was successfully integrated with the graphene material, (ii) a steady release of UA was documented, (iii) steady UA release ensured strong inhibition of bacterial biofilm formation. Interestingly, even after the initial burst release of UA, the second phase of steady release was sufficient to block bacterial colonization. Based on these results, we propose that graphene coatings loaded with UA can serve as effective antibiofilm protection of biomedical surfaces.

Evolutionary Analysis of the Bacillus subtilis Genome Reveals New Genes Involved in Sporulation

Bacilli can form dormant, highly resistant, and metabolically inactive spores to cope with extreme environmental challenges. In this study, we examined the evolutionary age of Bacillus subtilis sporulation genes using the approach known as genomic phylostratigraphy. We found that B. subtilis sporulation genes cluster in several groups that emerged at distant evolutionary time-points, suggesting that the sporulation process underwent several stages of expansion. Next, we asked whether such evolutionary stratification of the genome could be used to predict involvement in sporulation of presently uncharacterized genes (y-genes). We individually inactivated a representative sample of uncharacterized genes that arose during the same evolutionary periods as the known sporulation genes and tested the resulting strains for sporulation phenotypes. Sporulation was significantly affected in 16 out of 37 (43%) tested strains. In addition to expanding the knowledge base on B. subtilis sporulation, our findings suggest that evolutionary age could be used to help with genome mining.

Graphene-Based Antimicrobial Biomedical Surfaces

Biomedical application of graphene derivatives have been intensively studied in last decade. With the exceptional structural, thermal, electrical, and mechanical properties, these materials have attracted immense attention of biomedical scientists to utilize graphene derivatives in biomedical devices to improve their performance or to achieve desired functions. Surfaces of graphene derivatives including graphite, graphene, graphene oxide and reduce graphene oxide have been demonstrated to pave an excellent platform for antimicrobial behavior, enhanced biocompatibility, tissue engineering, biosensors and drug delivery. This review focuses on the recent advancement in the research of biomedical devices with the coatings or highly structured polymer nanocomposite surfaces of graphene derivatives for antimicrobial activity and sterile surfaces comprising an entirely new class of antibacterial materials. Overall, we aim to highlight on the potential of these materials, current understanding and knowledge gap in the antimicrobial behavior and biocompatibility to be utilized of their coatings to prevent the cross infections.

The Exo-Polysaccharide Component of Extracellular Matrix is Essential for the Viscoelastic Properties of Bacillus subtilis Biofilms

Bacteria are known to form biofilms on various surfaces. Biofilms are multicellular aggregates, held together by an extracellular matrix, which is composed of biological polymers. Three principal components of the biofilm matrix are exopolysaccharides (EPS), proteins, and nucleic acids. The biofilm matrix is essential for biofilms to remain organized under mechanical stress. Thanks to their polymeric nature, biofilms exhibit both elastic and viscous mechanical characteristics; therefore, an accurate mechanical description needs to take into account their viscoelastic nature. Their viscoelastic properties, including during their growth dynamics, are crucial for biofilm survival in many environments, particularly during infection processes. How changes in the composition of the biofilm matrix affect viscoelasticity has not been thoroughly investigated. In this study, we used interfacial rheology to study the contribution of the EPS component of the matrix to viscoelasticity of Bacillus subtilis biofilms. Two strategies were used to specifically deplete the EPS component of the biofilm matrix, namely (i) treatment with sub-lethal doses of vitamin C and (ii) seamless inactivation of the eps operon responsible for biosynthesis of the EPS. In both cases, the obtained results suggest that the EPS component of the matrix is essential for maintaining the viscoelastic properties of bacterial biofilms during their growth. If the EPS component of the matrix is depleted, the mechanical stability of biofilms is compromised and the biofilms become more susceptible to eradication by mechanical stress.

A Sustainable Approach for the Green Synthesis of Silver Nanoparticles from Solibacillus isronensis sp. and Their Application in Biofilm Inhibition

The use of bacteria as nanofactories for the green synthesis of nanoparticles is considered a sustainable approach, owing to the stability, biocompatibility, high yields and facile synthesis of nanoparticles. The green synthesis provides the coating or capping of biomolecules on nanoparticles surface, which confer their biological activity. In this study, we report green synthesis of silver nanoparticles (AgNPs) by an environmental isolate; named as AgNPs1, which showed 100% 16S rRNA sequence similarity with Solibacillus isronensis. UV/visible analysis (UV/Vis), transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the synthesized nanoparticles. The stable nature of nanoparticles was studied by thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS). Further, these nanoparticles were tested for biofilm inhibition against Escherichia coli and Pseudomonas aeruginosa. The AgNPs showed minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 3.12 µg/mL and 6.25 µg/mL for E. coli, and 1.56 µg/mL and 3.12 µg/mL for P. aeruginosa, respectively.

Precontrolled Alignment of Graphite Nanoplatelets in Polymeric Composites Prevents Bacterial Attachment

Graphene coatings composed of vertical spikes are shown to mitigate bacterial attachment. Such coatings present hydrophobic edges of graphene, which penetrate the lipid bilayers causing physical disruption of bacterial cells. However, manufacturing of such surfaces on a scale required for antibacterial applications is currently not feasible. This study explores whether graphite can be used as a cheaper alternative to graphene coatings. To examine this, composites of graphite nanoplatelets (GNP) and low-density polyethylene (LDPE) are extruded in controlled conditions to obtain controlled orientation of GNP flakes within the polymer matrix. Flakes are exposed by etching the surface of GNP-LDPE nanocomposites and antibacterial activity is evaluated. GNP nanoflakes on the extruded samples interact with bacterial cell membranes, physically damaging the cells. Bactericidal activity is observed dependent on orientation and nanoflakes density. Composites with high density of GNP (≥15%) present two key advantages: i) they decrease bacterial viability by a factor of 99.9999%, which is 10 000-fold improvement on the current benchmark, and ii) prevent bacterial colonization, thus drastically reducing the numbers of dead cells on the surface. The latter is a key advantage for longer-term biomedical applications, since these surfaces will not have to be cleaned or replaced for longer periods.

Graphene-based biosensors for the detection of prostate cancer protein biomarkers: a review

Prostate cancer (PC) is the sixth most common cancer type in the world, which causes approximately 10% of total cancer fatalities. The detection of protein biomarkers in body fluids is the key topic for the diagnosis and prognosis of PC. Highly sensitive screening of PC is the most effective approach for reducing mortality. Thus, there are a growing number of literature that recognizes the importance of new technologies for early diagnosis of PC. Graphene is playing an important role in the biosensor field with remarkable physical, optical, electrochemical and magnetic properties. Many recent studies demonstrated the potential of graphene materials for sensitive detection of protein biomarkers. In this review, the graphene-based biosensors toward PC analysis are mainly discussed in two groups: Firstly, novel biosensor interfaces were constructed through the modification of graphene materials onto sensor surfaces. Secondly, ingenious signal amplification strategies were developed using graphene materials as catalysts or carriers. Graphene-based biosensors have exhibited remarkable performance with high sensitivities, wide detection ranges, and long-term stabilities.

Biofilm Formation by Uropathogens and Their Susceptibility Towards Antimicrobial Therapy

Introduction: Urinary tract infection (UTI) is the most common health care associated infection caused by various pathogenic bacteria. Biofilms are communities of bacteria that are held together by exopolymeric substances that protect against the antimicrobial therapy and other environmental assaults. The aim of this study was to estimate the prevalence of biofilm forming bacteria in Nepalese population and to study the emergence of antimicrobial resistance among biofilm producing bacteria in comparison to non-biofilm producing bacteria. Methods: A total of 785 clean-caught-mid-stream urine samples were collected. After isolation and identification of uropathogens, they were further processed for detection of biofilm formation by two methods (Congo Red Agar method and Tissue Culture Plate method) as well as for antibiotic sensitivity test. Results: Out of total collected samples, 12.74% were found to be associated with UTI, among them 67% were Escherichia coli, 10% were Klebsiella spp, 7% were Pseudomonas spp, 6% were Staphyloccous aureus, 4% were Enterobacter spp, 3% were Proteus spp, 2% were Citrobacter spp and remaining 1% was Staphylococcus saprophyticus. Among isolated organisms, the ratio of bioflim positive organism to bioflim negative organism was found to be 9:11. Nitrofurantoin, Tobramycin, Chloramphenicol, Amikacin and Imipenem were found to be significantly more sensitive in biofilm negative bacteria as compared to biofilm positive bacteria with p values of 0.000, 0.001, 0.000, 0.000 and 0.001. Conclusions: The prevalence rate of multidrug resistance in bacterial uropathogens was higher in biofilm producers as compared to non-biofilm producers. Biofilm forming characteristic of bacteria make them more resistant to antibiotics.

Antibacterial effect of boron nitride flakes with controlled orientation in polymer composites

Boron nitride (BN) is a stable 2D material with physiochemical properties similar to graphene-based nanomaterials. We have recently demonstrated that vertically aligned coatings of graphene-based nanomaterials provide strong antibacterial effects on various surfaces. Here we investigated whether BN, a nanomaterial with extensive similarities to graphene, might exhibit similar antibacterial properties. To test this, we developed a novel composite material using BN and low density polyethylene (LDPE) polymer. The composite was extruded under controlled melt flow conditions leading to highly structured morphology, with BN oriented in the extrusion flow direction. Nanocomposite extruded surfaces perpendicular to the flow direction were etched, thus exposing BN nanoparticles embedded in the matrix. The antimicrobial activity of extruded samples was evaluated against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis and Staphylococcus aureus by the colony forming units (CFUs) counting method. Furthermore, the bactericidal effect of oriented BN against E. coli and S. aureus was evaluated by scanning electron microscopy (SEM) and live/dead viability assay. Our results suggest that BN nanoflakes on the extruded BN/LDPE composite physically interact with the bacterial cellular envelope, leading to irreparable physical damage. Therefore, we propose that BN–polymer composites might be useful to develop polymer based biomedical devices protected against bacterial adhesion, and thus minimize device associated infections.

Vertically oriented boron nitride flakes on a polymer surface exhibit bactericidal activity.

Antimicrobial Effects of Biogenic Nanoparticles

Infectious diseases pose one of the greatest health challenges in the medical world. Though numerous antimicrobial drugs are commercially available, they often lack effectiveness against recently developed multidrug resistant (MDR) microorganisms. This results in high antibiotic dose administration and a need to develop new antibiotics, which in turn requires time, money, and labor investments. Recently, biogenic metallic nanoparticles have proven their effectiveness against MDR microorganisms, individually and in synergy with the current/conventional antibiotics. Importantly, biogenic nanoparticles are easy to produce, facile, biocompatible, and environmentally friendly in nature. In addition, biogenic nanoparticles are surrounded by capping layers, which provide them with biocompatibility and long-term stability. Moreover, these capping layers provide an active surface for interaction with biological components, facilitated by free active surface functional groups. These groups are available for modification, such as conjugation with antimicrobial drugs, genes, and peptides, in order to enhance their efficacy and delivery. This review summarizes the conventional antibiotic treatments and highlights the benefits of using nanoparticles in combating infectious diseases.

Bacterial response to graphene oxide and reduced graphene oxide integrated in agar plates

There are contradictory reports in the literature regarding the anti-bacterial activity of graphene, graphene oxide (GO) and reduced graphene oxide (rGO). This controversy is mostly due to variations in key parameters of the reported experiments, like: type of substrate, form of graphene, number of layers, type of solvent and most importantly, type of bacteria. Here, we present experimental data related to bacterial response to GO and rGO integrated in solid agar-based nutrient plates-a standard set-up for bacterial growth that is widely used by microbiologists. Bacillus subtilis and Pseudomonas aeruginosa strains were used for testing bacterial growth. We observed that plate-integrated rGO showed strong anti-bacterial activity against both bacterial species. By contrast, plate-integrated GO was harmless to both bacteria. These results reinforce the notion that the response of bacteria depends critically on the type of graphene material used and can vary dramatically from one bacterial strain to another, depending on bacterial physiology.

Green synthesis of gold and silver nanoparticles from Cannabis sativa (industrial hemp) and their capacity for biofilm inhibition

Background

Cannabis sativa (hemp) is a source of various biologically active compounds, for instance, cannabinoids, terpenes and phenolic compounds, which exhibit antibacterial, antifungal, anti-inflammatory and anticancer properties. With the purpose of expanding the auxiliary application of C. sativa in the field of bio-nanotechnology, we explored the plant for green and efficient synthesis of gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs).

Methods and results

The nanoparticles were synthesized by utilizing an aqueous extract of C. sativa stem separated into two different fractions (cortex and core [xylem part]) without any additional reducing, stabilizing and capping agents. In the synthesis of AuNPs using the cortex enriched in bast fibers, fiber-AuNPs (F-AuNPs) were achieved. When using the core part of the stem, which is enriched with phenolic compounds such as alkaloids and cannabinoids, core-AuNPs (C-AuNPs) and core-AgNPs (C-AgNPs) were formed. Synthesized nanoparticles were character-ized by UV–visible analysis, transmission electron microscopy, atomic force microscopy, dynamic light scattering, Fourier transform infrared, and matrix-assisted laser desorption/ionization time-of-flight. In addition, the stable nature of nanoparticles has been shown by thermogravimetric analysis and inductively coupled plasma mass spectrometry (ICP-MS). Finally, the AgNPs were explored for the inhibition of Pseudomonas aeruginosa and Escherichia coli biofilms.

Conclusion

The synthesized nanoparticles were crystalline with an average diameter between 12 and 18 nm for F-AuNPs and C-AuNPs and in the range of 20–40 nm for C-AgNPs. ICP-MS analysis revealed concentrations of synthesized nanoparticles as 0.7, 4.5 and 3.6 mg/mL for F-AuNPs, C-AuNPs and C-AgNPs, respectively. Fourier transform infrared spectroscopy revealed the presence of flavonoids, cannabinoids, terpenes and phenols on the nanoparticle surface, which could be responsible for reducing the salts to nanoparticles and further stabilizing them. In addition, the stable nature of synthesized nanoparticles has been shown by thermogravimetric analysis and ICP-MS. Finally, the AgNPs were explored for the inhibition of P. aeruginosa and E. coli biofilms. The nanoparticles exhibited minimum inhibitory concentration values of 6.25 and 5 µg/mL and minimum bactericidal concentration values of 12.5 and 25 µg/mL against P. aeruginosa and E. coli, respectively.

Effect of brief periodic fluoride treatments on the virulence and composition of a cariogenic biofilm

The present study investigated the effect of periodic 1-min fluoride treatments on Streptococcus mutans biofilms and then determined the relationship between anti-biofilm activity, treatment frequency, and fluoride concentration using a linear-fitting procedure. S. mutans biofilms were periodically treated (1-min/treatment) with fluoride during biofilm formation and analyzed using microbiological methods, confocal microscopy, and real-time PCR. The results indicated that reductions in the dry weight and acidogenicity of biofilms due to periodic fluoride treatment occurred in a concentration dependent manner. The reduction in dry weight without affecting bacterial cell viability was observed mainly due to the inhibitory effect of fluoride on gtfB and gtfC gene expression, which suppresses EPS production and avoids reduction of the pH below the critical point on the tooth surface. This study suggests that brief periodic exposure to appropriate fluoride concentrations through mouthwashes and toothpastes may affect the virulence and composition of cariogenic biofilms and subsequently prevent dental caries.

Boron nitride nanomaterials: biocompatibility and bio-applications

Boron nitride has structural characteristics similar to carbon 2D materials (graphene and its derivatives) and its layered structure has been exploited to form different nanostructures such as nanohorns, nanotubes, nanoparticles and nanosheets.

Low Concentrations of Vitamin C Reduce the Synthesis of Extracellular Polymers and Destabilize Bacterial Biofilms

Extracellular polymeric substances (EPS) produced by bacteria form a matrix supporting the complex three-dimensional architecture of biofilms. This EPS matrix is primarily composed of polysaccharides, proteins and extracellular DNA. In addition to supporting the community structure, the EPS matrix protects bacterial biofilms from the environment. Specifically, it shields the bacterial cells inside the biofilm, by preventing antimicrobial agents from getting in contact with them, thereby reducing their killing effect. New strategies for disrupting the formation of the EPS matrix can therefore lead to a more efficient use of existing antimicrobials. Here we examined the mechanism of the known effect of vitamin C (sodium ascorbate) on enhancing the activity of various antibacterial agents. Our quantitative proteomics analysis shows that non-lethal concentrations of vitamin C inhibit bacterial quorum sensing and other regulatory mechanisms underpinning biofilm development. As a result, the EPS biosynthesis in reduced, and especially the polysaccharide component of the matrix is depleted. Once the EPS content is reduced beyond a critical point, bacterial cells get fully exposed to the medium. At this stage, the cells are more susceptible to killing, either by vitamin C-induced oxidative stress as reported here, or by other antimicrobials or treatments.

Vitamin C Pretreatment Enhances the Antibacterial Effect of Cold Atmospheric Plasma

Bacterial biofilms are three-dimensional structures containing bacterial cells enveloped in a protective polymeric matrix, which renders them highly resistant to antibiotics and the human immune system. Therefore, the capacity to make biofilms is considered as a major virulence factor for pathogenic bacteria. Cold Atmospheric Plasma (CAP) is known to be quite efficient in eradicating planktonic bacteria, but its effectiveness against biofilms has not been thoroughly investigated. The goal of this study was to evaluate the effect of exposure of CAP against mature biofilm for different time intervals and to evaluate the effect of combined treatment with vitamin C. We demonstrate that CAP is not very effective against 48 h mature bacterial biofilms of several common opportunistic pathogens: Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa. However, if bacterial biofilms are pre-treated with vitamin C for 15 min before exposure to CAP, a significantly stronger bactericidal effect can be obtained. Vitamin C pretreatment enhances the bactericidal effect of cold plasma by reducing the viability from 10 to 2% in E. coli biofilm, 50 to 11% in P. aeruginosa, and 61 to 18% in S. epidermidis biofilm. Since it is not feasible to use extended CAP treatments in medical practice, we argue that the pre-treatment of infectious lesions with vitamin C prior to CAP exposure can be a viable route for efficient eradication of bacterial biofilms in many different applications.

Graphene based nanosensor for aqueous phase detection of nitroaromatics

Nitroaromatics sensor composed of monolayer graphene and molecularly imprinted chitosan thin film was fabricated and responded selectively against imprinted nitrotriazolone.

Ventricular Aneurysm as a cause for post traumatic tachycardia – a case report

The purpose of this case is to illustrate an interesting cause of a common symptom. It is designed to make the reader aware of the possibility of post traumatic ventricular aneurysm. It also illustrates the difficulty involved in making an unusual diagnosis in the Intensive Care setting.

Effect of multi-nutrient insufficiency on markers of one carbon metabolism in young women: response to a methionine load

BACKGROUND/OBJECTIVES

Multi-nutrient insufficiencies as a consequence of nutritional and economic factors are common in India and other developing countries. We have examined the impact of multi-nutrient insufficiency on markers of one carbon (1C) metabolism in the blood, and response to a methionine load in clinically healthy young women.

SUBJECTS/METHODS

Young women from Pune, India (n=10) and Cleveland, USA (n=13) were studied. Blood samples were obtained in the basal state and following an oral methionine load (50 mg/kg of body weight in orange juice). Plasma concentrations of vitamin B12, folate and B6 were measured in the basal state. The effect of methionine load on the levels of methionine, total homocysteine, cysteine, glutathione and amino acids was examined.

RESULTS

Indian women were significantly shorter and lighter compared with the American women and had lower plasma concentration of vitamins B12, folate and B6, essential amino acids and glutathione, but higher concentration of total homocysteine. The homocysteine response to methionine load was higher in Indian women. The plasma concentrations of glycine and serine increased in the Indian women after methionine (in juice) load. A significant negative correlation between plasma B6 and homocysteine (r= -0.70), and plasma folate and glycine and serine levels were observed in the Indian group (P<0.05) but not in the American group.

CONCLUSIONS

Multi-nutrient insufficiency in the Indian women caused unique changes in markers of whole body protein and 1C metabolism. These data would be useful in developing nutrient intervention strategies.

A Rare Case of Bilateral Aspergillomas in a Patient of Ankylosing Spondylitis

Pulmonary involvement by Aspergillus sp. mainly includes allergic bronchopulmonary aspergillosis, aspergilloma, and invasive aspergillosis. Aspergilloma (Fungal ball) is the most common form of aspergillous pulmonary involvement, which occurs in preexisting pulmonary cavities, especially secondary to pulmonary tuberculosis. Ankylosing spondylitis is a rare cause of upper lobe fibro-cavitary lesions in pulmonary parenchyma. It may also lead to development of fungal balls in pulmonary cavities. Most common presentation is mild to massive hemoptysis; dyspnoea, chronic cough, expectoration may be other presentation; even the patient may remain asymptomatic. Intaracavitary mobile mass is a valuable sign for fungal ball, best detected by computed tomography (CT) scan of thorax. Lobectomy is the treatment of choice to stop the hemoptysis, if the general condition of the patient is fit; otherwise associated co-morbidities complicate the post-operative scenario. In this situation, bronchial artery embolization may be used as a temporary measure to control hemoptysis. Here, we report a case of bilateral aspergillomas within the cavities located in upper lobes of both lungs in a 74 years old male who was suffering from ankylosing spondylitis for last 42 years.

Graphene oxide based coatings on nitinol for biomedical implant applications: effectively promote mammalian cell growth but kill bacteria

Graphene oxide based coating significantly enhances the proliferation of osteoblastic cells and shows toxicity towards the bacterial cells.

NaB integrated graphene oxide membranes for enhanced cell viability and stem cell properties of human adipose stem cells

A ready-made NaB integrated GO membrane platform to study the long term stem cell viability and enhanced proliferation of hASCs.