Current paradigms and future challenges in harnessing gut bacterial symbionts of insects for biodegradation of plastic wastes.

The ubiquitous incorporation of plastics into daily life, coupled with inefficient recycling practices, has resulted in the accumulation of millions of metric tons of plastic waste, that poses a serious threat to the Earth's sustainability. Plastic pollution, a global problem, disrupts the ecological balance and endangers various life forms. Efforts to combat plastic pollution are underway, with a promising avenue being biological degradation facilitated by certain insects and their symbiotic gut microorganisms, particularly bacteria. This review consolidates existing knowledge on plastic degradation by insects and their influence on gut microbiota. Additionally, it delves into the potential mechanisms employed by insects in symbiosis with gut bacteria, exploring the bioconversion of waste plastics into value-added biodegradable polymers through mineralization. These insights hold significant promise for the bio-upcycling of plastic waste, opening new horizons for future biomanufacturing of high-value chemicals from plastic-derived compounds. Finally, we weigh the pros and cons of future research endeavors related to the bioprospection of plastic-degrading bacteria from underexplored insect species. We also underscore the importance of bioengineering depolymerases with novel characteristics, aiming for their application in the remediation and valorization of waste plastics.

Multichannel bridges and NSC synergize to enhance axon regeneration, myelination, synaptic reconnection, and recovery after SCI.

Regeneration in the injured spinal cord is limited by physical and chemical barriers. Acute implantation of a multichannel poly(lactide-co-glycolide) (PLG) bridge mechanically stabilizes the injury, modulates inflammation, and provides a permissive environment for rapid cellularization and robust axonal regrowth through this otherwise inhibitory milieu. However, without additional intervention, regenerated axons remain largely unmyelinated (<10%), limiting functional repair. While transplanted human neural stem cells (hNSC) myelinate axons after spinal cord injury (SCI), hNSC fate is highly influenced by the SCI inflammatory microenvironment, also limiting functional repair. Accordingly, we investigated the combination of PLG scaffold bridges with hNSC to improve histological and functional outcome after SCI. In vitro, hNSC culture on a PLG scaffold increased oligodendroglial lineage selection after inflammatory challenge. In vivo, acute PLG bridge implantation followed by chronic hNSC transplantation demonstrated a robust capacity of donor human cells to migrate into PLG bridge channels along regenerating axons and integrate into the host spinal cord as myelinating oligodendrocytes and synaptically integrated neurons. Axons that regenerated through the PLG bridge formed synaptic circuits that connected the ipsilateral forelimb muscle to contralateral motor cortex. hNSC transplantation significantly enhanced the total number of regenerating and myelinated axons identified within the PLG bridge. Finally, the combination of acute bridge implantation and hNSC transplantation exhibited robust improvement in locomotor recovery. These data identify a successful strategy to enhance neurorepair through a temporally layered approach using acute bridge implantation and chronic cell transplantation to spare tissue, promote regeneration, and maximize the function of new axonal connections.

Revealing bacterial and fungal communities of the untapped forest and alpine grassland zones of the Western-Himalayan region.

The Western Himalayas offer diverse environments for investigating the diversity and distribution of microbial communities and their response to both the abiotic and biotic factors across the entire altitudinal gradient. Such investigations contribute significantly to our understanding of the complex ecological processes that shape microbial diversity. The proposed study focuses on the investigation of the bacterial and fungal communities in the forest and alpine grasslands of the Western Himalayan region, as well as their relationship with the physicochemical parameters of soil. A total of 185 isolates were obtained using the culture-based technique belonging to Bacillus (37%), Micrococcus (16%), and Staphylococcus (7%). Targeted metagenomics revealed the abundance of bacterial phyla Pseudomonadota (23%) followed by Acidobacteriota (20.2%), Chloroflexota (15%), and Bacillota (11.3%). At the genera level, CandidatusUdaeobacter (6%), Subgroup_2 (5.5%) of phylum Acidobacteriota, and uncultured Ktedonobacterales HSB_OF53-F07 (5.2%) of Choloroflexota phylum were found to be preponderant. Mycobiome predominantly comprised of phyla Ascomycota (54.1%), Basidiomycota (24%), and Mortierellomycota (19.1%) with Archaeorhizomyces (19.1%), Mortierella (19.1%), and Russula (5.4%) being the most abundant genera. Spearman's correlation revealed that the bacterial community was most influenced by total nitrogen in the soil followed by soil organic carbon as compared to other soil physicochemical factors. The study establishes a fundamental relationship between microbial communities and the physicochemical properties of soil. Furthermore, the study provides valuable insights into the complex interplay between biotic and abiotic factors that influence the microbial community composition of this unique region across various elevations.

Multichannel bridges and NSC synergize to enhance axon regeneration, myelination, synaptic reconnection, and recovery after SCI.

Regeneration in the injured spinal cord is limited by physical and chemical barriers. Acute implantation of a multichannel poly(lactide-co-glycolide) (PLG) bridge mechanically stabilizes the injury, modulates inflammation, and provides a permissive environment for rapid cellularization and robust axonal regrowth through this otherwise inhibitory milieu. However, without additional intervention, regenerated axons remain largely unmyelinated (<10%), limiting functional repair. While transplanted human neural stem cells (hNSC) myelinate axons after spinal cord injury (SCI), hNSC fate is highly influenced by the SCI inflammatory microenvironment, also limiting functional repair. Accordingly, we investigated the combination of PLG scaffold bridges with hNSC to improve histological and functional outcome after SCI. In vitro, hNSC culture on a PLG scaffold increased oligodendroglial lineage selection after inflammatory challenge. In vivo, acute PLG bridge implantation followed by chronic hNSC transplantation demonstrated a robust capacity of donor human cells to migrate into PLG bridge channels along regenerating axons and integrate into the host spinal cord as myelinating oligodendrocytes and synaptically integrated neurons. Axons that regenerated through the PLG bridge formed synaptic circuits that connected ipsilateral forelimb muscle to contralateral motor cortex. hNSC transplantation significantly enhanced the total number of regenerating and myelinated axons identified within the PLG bridge. Finally, the combination of acute bridge implantation and hNSC transplantation exhibited robust improvement in locomotor recovery vs. control and hNSC transplant alone. These data identify a successful novel strategy to enhance neurorepair through a temporally layered approach using acute bridge implantation and chronic cell transplantation to spare tissue, promote regeneration, and maximize the function of new axonal connections.

Host-Specific Diversity of Culturable Bacteria in the Gut Systems of Fungus-Growing Termites and Their Potential Functions towards Lignocellulose Bioconversion.

Fungus-growing termites are eusocial insects that represent one of the most efficient and unique systems for lignocellulose bioconversion, evolved from a sophisticated symbiosis with lignocellulolytic fungi and gut bacterial communities. Despite a plethora of information generated during the last century, some essential information on gut bacterial profiles and their unique contributions to wood digestion in some fungus-growing termites is still inadequate. Hence, using the culture-dependent approach, the present study aims to assess and compare the diversity of lignocellulose-degrading bacterial symbionts within the gut systems of three fungus-growing termites: Ancistrotermes pakistanicus, Odontotermes longignathus, and Macrotermes sp. A total of 32 bacterial species, belonging to 18 genera and 10 different families, were successfully isolated and identified from three fungus-growing termites using Avicel or xylan as the sole source of carbon. Enterobacteriaceae was the most dominant family represented by 68.1% of the total bacteria, followed by Yersiniaceae (10.6%) and Moraxellaceae (9%). Interestingly, five bacterial genera such as Enterobacter, Citrobacter, Acinetobacter, Trabulsiella, and Kluyvera were common among the tested termites, while the other bacteria demonstrated a termite-specific distribution. Further, the lignocellulolytic potential of selected bacterial strains was tested on agricultural waste to evaluate their capability for lignocellulose bioconversion. The highest substrate degradation was achieved with E. chengduensis MA11 which degraded 45.52% of rice straw. All of the potential strains showed endoglucanase, exoglucanase, and xylanase activities depicting a symbiotic role towards the lignocellulose digestion within the termite gut. The above results indicated that fungus-growing termites harbor a diverse array of bacterial symbionts that differ from species to species, which may play an inevitable role to enhance the degradation efficacy in lignocellulose decomposition. The present study further elaborates our knowledge about the termite-bacteria symbiosis for lignocellulose bioconversion which could be helpful to design a future biorefinery.

Nanoclays for wound management applications.

Nanotechnology has been comprehensively applied as a new approach to managing wound healing. Particularly, nanoclays are being used to improve traditional wound healing approaches or new therapies. Nanoclays are nanoscale aluminosilicates with remarkable intrinsic properties, including the capacity to promote hemostatic response, anti-inflammatory effects, angiogenesis, and re-epithelization. The main purpose of the present review is focusing on skin lesions, post-surgical wounds, burn wounds, and chronic ulcer skin wounds that can be treated using nanoclays, not only as vehicles for therapeutic molecules' efficacy improvement but also alone due to their native beneficial features. A systematic search of the PubMed, ScienceDirect, Scopus, Web of Science, and Google Scholar databases revealed several studies satisfying the purpose of our study. In addition, the selected keywords were used to refine the information. Non-planar hydrous phyllosilicates have been compared with other nanoclays considering their acute specific surface area and loading capacity are strongly influenced by their structure. Nanocomposites in the powder form may be directly incorporated in polymers to form gels, biofilms, and scaffolds that may be adjustable to wound sites. Also, nanoclays can be directly incorporated into polymer mats. Regarding hydrogels/films and mats, nanoclays can improve their mechanical strength, thermal stability, viscosity, and cohesive strength. Additionally, nanoclays are able to control drug release, as well as their skin bioavailability, and seem to be promising candidates to overcome cytotoxicity problems; further in vivo toxicity studies are required.

Cyclodextrin-based dermatological formulations: Dermopharmaceutical and cosmetic applications.

The progress in new delivery systems for active ingredients has boosted the dermopharmaceutical and cosmetic fields by allowing formulations to display enhanced skin permeation capabilities. Cyclodextrins (CDs) are cyclic oligosaccharides able to form host-guest inclusion complexes with guest active molecules, resulting in improved physicochemical properties of such molecules. The incorporation of CDs in dermopharmaceutical and cosmetics formulations has received much attention since the late 1970 s by enhancing modulation of the passage through the skin and vectorization into the target site while simultaneously offering a biocompatible delivery system. This paper features the advantages of CDs in dermopharmaceutical and cosmetic applications, such as the improvement of the apparent solubility and the stability of the active ingredients, the possibility of masking unpleasant odors, among others that are be described, emphasizing that these versatile skin active ingredient carriers are strongly promising both in the treatment of skin diseases and in the improvement of cosmetic formulations.

Adsorption and removal of ethidium bromide from aqueous solution using optimized biogenic catalytically active antibacterial palladium nanoparticles.

Due to being low cost and eco-friendly, biological nanomaterial synthesis and development have made broad spectral progress. This study aimed to optimize the phytomediated synthesis of catalytically active, antibacterial palladium nanoparticles (PdNPs) for adsorption-based removal of ethidium bromide (EtBr) from an aqueous solution. Optimization of synthesis demonstrated that a precursor to extract ratio of 4:1, pH 3, and incubation at 80 °C for 60 min were the optimum conditions that led to the synthesis of negatively charged, highly stable, polycrystalline, spherical, and monodispersed PdNPs of 5-10 nm. When tested as catalysts, PdNPs successfully catalyzed Suzuki-Miyaura cross-coupling between aryl halides and arylboronic acids resulting in the synthesis of 4-acetylbiphenyl. Furthermore, the antibacterial activity test demonstrated that biogenic PdNPs were most effective and potent against Staphylococcus aureus and Proteus vulgaris followed by Escherichia coli, Bacillus subtilis, and Bacillus cereus. In addition, PdNPs were found as an excellent adsorbent for adsorption of EtBr from water as the adsorption reaction obeyed pseudo-second-order kinetics with a linear regression coefficient (R2 > 0.995). The adsorption reaction fitted well with the Freundlich and Temkin isotherm models, indicating multi-layer adsorption. Estimating thermodynamic parameters resulted in a positive value of ΔH0 and ΔG0, demonstrating adsorption was non-spontaneous and endothermic.

Rectal Application of Lidocaine Reduces the Severity of Autonomic Dysreflexia following Experimental Spinal Cord Injury.

Spinal cord injury (SCI) results in devastating cardiovascular dysfunction. Noxious stimuli from the rectum during bowel routine often trigger life-threatening blood pressure surges, termed autonomic dysreflexia (AD). Rectal application of anesthetic lidocaine jelly has been recommended during bowel care to reduce AD severity by mitigating sensory input. However, clinical studies have reported contradicting evidence. We performed a pre-clinical study on the efficacy of rectal lidocaine in a standardized rodent T3 transection model. We found that 2% and 10% lidocaine significantly reduced AD severity by 32% and 50%, respectively, compared with control (p < 0.0001). Our pre-clinical experiments support the current recommendation of rectal lidocaine application during bowel care.

Application of nanotechnology in management and treatment of diabetic wounds.

Diabetic wounds are one of the most common health problems worldwide, enhancing the demand for new management strategies. Nanotechnology, as a developing subject in diabetic wound healing, is proving to be a promising and effective tool in treatment and care. It is, therefore, necessary to ascertain the available and distinct nanosystems and evaluate their performance when topically applied to the injury site, especially in diabetic wound healing. Several active ingredients, including bioactive ingredients, growth factors, mesenchymal stem cells, nucleic acids, and drugs, benefit from improved properties when loaded into nanosystems. Given the risk of problems associated with systemic administration, the topical application should be considered, provided stability and efficacy are assured. After nanoencapsulation, active ingredients-loaded nanosystems have been showing remarkable features of biocompatibility, healing process hastening, angiogenesis, and extracellular matrix compounds synthesis stimulation, contributing to a decrease in wound inflammation. Despite limitations, nanotechnology has attracted widespread attention in the scientific community and seems to be a valuable technological ally in the treatment and dressing of diabetic wounds. The use of nanotechnology in topical applications enables efficient delivery of the active ingredients to the specific skin site, increasing their bioavailability, stability, and half-life time, without compromising their safety.

Valorization Potential of a Novel Bacterial Strain, Bacillus altitudinis RSP75, towards Lignocellulose Bioconversion: An Assessment of Symbiotic Bacteria from the Stored Grain Pest, Tribolium castaneum.

Bioconversion of lignocellulose into renewable energy and commodity products faces a major obstacle of inefficient saccharification due to its recalcitrant structure. In nature, lignocellulose is efficiently degraded by some insects, including termites and beetles, potentially due to the contribution from symbiotic gut bacteria. To this end, the presented investigation reports the isolation and characterization of cellulolytic bacteria from the gut system of red flour beetle, Tribolium castaneum. Out of the 15 isolated bacteria, strain RSP75 showed the highest cellulolytic activities by forming a clearance zone of 28 mm in diameter with a hydrolytic capacity of ~4.7. The MALDI-TOF biotyping and 16S rRNA gene sequencing revealed that the strain RSP75 belongs to Bacillus altitudinis. Among the tested enzymes, B. altitudinis RSP75 showed maximum activity of 63.2 IU/mL extract for xylanase followed by ß-glucosidase (47.1 ± 3 IU/mL extract) which were manifold higher than previously reported activities. The highest substrate degradation was achieved with wheat husk and corn cob powder which accounted for 69.2% and 54.5%, respectively. The scanning electron microscopy showed adhesion of the bacterial cells with the substrate which was further substantiated by FTIR analysis that depicted the absence of the characteristic cellulose bands at wave numbers 1247, 1375, and 1735 cm-1 due to hydrolysis by the bacterium. Furthermore, B. altitudinis RSP75 showed co-culturing competence with Saccharomyces cerevisiae for bioethanol production from lignocellulose as revealed by GC-MS analysis. The overall observations signify the gut of T. castaneum as a unique and impressive reservoir to prospect for lignocellulose-degrading bacteria that can have many biotechnological applications, including biofuels and biorefinery.

Nanotechnology-based formulations toward the improved topical delivery of anti-acne active ingredients.

Introduction: Acne vulgaris is a chronic inflammatory skin disorder that affects an extremely concerning percentage of teenagers (ca. 85%), gathering serious negative impacts on the social life and psychological well-being of individuals. Conventional topical formulations for acne show low tolerability and side effects, such as skin irritation, leading to a decrease in the user's adherence to therapy. Nanotechnology-based formulations were developed as new strategies for topical acne management, particularly to overcome the difficulties associated with conventional treatments.Areas covered: This paper presents a critical analysis of reviewed nanosized anti-acne technological strategies, strongly supporting controlled active ingredient release, improved skin permeation, and lower skin irritation. An updated regulatory framework, considering the promising applications in nanomedicine, and the toxicity of these nanosystems are also addressed.Expert opinion: Nanosystems evidence several advantages, attending to the possibility of controlled active ingredient release, better skin permeation, and lower skin irritation. However, novel nanotechnological strategies for acne treatment and care can lead to new side effects, but also environmental nano pollution. Little is known about the toxicology of these nanotechnology-based formulations, therefore, as future trends, more studies should be conducted to assure the consumers' health and environmental safety.

Noninvasive Neuroprosthesis Promotes Cardiovascular Recovery After Spinal Cord Injury.

Spinal cord injury (SCI) leads to severe impairment in cardiovascular control, commonly manifested as a rapid, uncontrolled rise in blood pressure triggered by peripheral stimuli-a condition called autonomic dysreflexia. The objective was to demonstrate the translational potential of noninvasive transcutaneous stimulation (TCS) in mitigating autonomic dysreflexia following SCI, using pre-clinical evidence and a clinical case report. In rats with SCI, we show that TCS not only prevents the instigation of autonomic dysreflexia, but also mitigates its severity when delivered during an already-triggered episode. Furthermore, when TCS was delivered as a multisession therapy for 6 weeks post-SCI, the severity of autonomic dysreflexia was significantly reduced when tested in the absence of concurrent TCS. This treatment effect persisted for at least 1 week after the end of therapy. More importantly, we demonstrate the clinical applicability of TCS in treatment of autonomic dysreflexia in an individual with cervical, motor-complete, chronic SCI. We anticipate that TCS will offer significant therapeutic advantages, such as obviating the need for surgery resulting in reduced risk and medical expenses. Furthermore, this study provides a framework for testing the potential of TCS in improving recovery of other autonomic functions such lower urinary tract, bowel, and sexual dysfunction following SCI.

Engineering the liposomal formulations from natural peanut phospholipids for pH and temperature sensitive release of folic acid, levodopa and camptothecin.

The present study demonstrates the extraction and identification of phospholipids (PLs) from peanut seed for formulation of liposomes for pH and thermo-sensitive delivery and release of folic acid (FA), levodopa (DOPA) and, camptothecin (CPT). The TLC, FTIR and GC-MS based characterization of extracted peanut PLs showed phosphatidylethanolamine, cardiolipin and phosphatidic acid as major PLs and palmitic acid and oleic acid as major fatty acids. Liposomes (LSMs) of size 1-2 µm formulated by optimized thin-film hydration method were found to entrap FA, DOPA and CPT with 58, 61.4 and 52.12% efficiency, respectively with good stability. The effect of external stimuli like pH and temperature on the release pattern of FA, DOPA and CPT indicated that FA was optimally released at pH 10 and 57 °C, DOPA at pH 2 and 37 °C, while CPT was best released at pH 6 and 47 °C. When tested for the in vitro activity, DOPA released by DOPA@LSMs showed lower toxicity to 3T3 than to SH-SY5Y cells. Similarly, CPT released by CPT@LSMs showed remarkable anticancer activity against MCF-7 cells with an IC50 value of 17.99 µg/mL. Thus peanut PLs can be efficiently used for liposomal formulations for pH and thermo-sensitive release of drugs.

Optimally biosynthesized, PEGylated gold nanoparticles functionalized with quercetin and camptothecin enhance potential anti-inflammatory, anti-cancer and anti-angiogenic activities.

BACKGROUND: The development of nano delivery systems is rapidly emerging area of nanotechnology applications where nanomaterials (NMs) are employed to deliver therapeutic agents to specific site in a controlled manner. To accomplish this, green synthesis of NMs is widely explored as an eco-friendly method for the development of smart drug delivery system. In the recent times, use of green synthesized NMs, especially metallic NMs have fascinated the scientific community as they are excellent carriers for drugs. This work demonstrates optimized green, biogenic synthesis of gold nanoparticles (AuNPs) for functionalization with quercetin (QT) and camptothecin (CPT) to enhance potential anti-inflammatory, anti-cancer and anti-angiogenic activities of these drugs. RESULTS: Gold nanoparticles were optimally synthesized in 8 min of reaction at 90 °C, pH 6, using 4 mM of HAuCl4 and 4:1 ratio of extract: HAuCl4. Among different capping agents tested, capping of AuNPs with polyethylene glycol 9000 (PG9) was found best suited prior to functionalization. PG9 capped AuNPs were optimally functionalized with QT in 1 h reaction at 70 °C, pH 7, using 1200 ppm of QT and 1:4 ratio of AuNPs-PG9:QT whereas, CPT was best functionalized at RT in 1 h, pH 12, AuNPs-PG9:CPT ratio of 1:1, and 0.5 mM of CPT. QT functionalized AuNPs showed good anti-cancer activity (IC50 687.44 µg/mL) against MCF-7 cell line whereas test of anti-inflammatory activity also showed excellent activity (IC50 287.177 mg/L). The CAM based assessment of anti-angiogenic activity of CPT functionalized AuNPs demonstrated the inhibition of blood vessel branching confirming the anti-angiogenic effect. CONCLUSIONS: Thus, present study demonstrates that optimally synthesized biogenic AuNPs are best suited for the functionalization with drugs such as QT and CPT. The functionalization of these drugs with biogenic AuNPs enhances the potential anti-inflammatory, anti-cancer and anti-angiogenic activities of these drugs, therefore can be used in biomedical application.

Almond skin extract mediated optimally biosynthesized antibacterial silver nanoparticles enable selective and sensitive colorimetric detection of Fe+2 ions.

The safety of drinking water is one of the most important public health issues as very high concentrations of metal like iron acts as a useful surrogate for other heavy metals. The present study demonstrates the use of almond skin extract (ASE) for simple and rapid synthesis of antibacterial silver nanoparticles (AgNPs) for the development of a highly selective and sensitive colorimetric method for the detection of Fe+2 in water samples. The optimization of various biogenic synthesis parameters showed ASE:AgNO3 ratio of 4:1,1 mM of AgNO3, pH 6 and incubation for 10 min at 70 °C were the optimum conditions. The test of antibacterial activity against widely used, representative Gram-negative and positive bacteria showed that AgNPs exhibit good activity against all five tested bacterial strains and comparatively were more effective against Gram-negative bacteria. Further, the test of AgNPs as a colorimetric probe for the detection of 20 different metal ions demonstrated that AgNPs were highly selective and sensitive towards the detection of Fe+2. The study of sensitivity of Fe+2 detection showed 245 ppm as the Limit of detection whereas, the intra-day recovery of Fe+2 in the range of 87.2-100.1 % with %RSD in the range of 4.2-6.5 % and inter-day recovery of Fe+2 in the range of 92.02-96.59 % with %RSD in the range of 2.9-3.8 % demonstrated the excellent precision and accuracy of the assay method. Thus, our AgNPs based selective and sensitive assay can be applied to the analysis of iron in drinking water samples.

Sustainable approach to almond skin mediated synthesis of tunable selenium microstructures for coating cotton fabric to impart specific antibacterial activity.

Currently, the synthesis of nanostructured inorganic materials with tunable morphology is still a great challenge. In this study, almond skin extract was employed for the biogenic synthesis of selenium nanoparticles with tunable morphologies such as rods and brooms. The effects of various synthesis parameters on morphologies were investigated using UV-Visible spectroscopy and scanning electron microscopy (SEM) which indicated that selenium brooms (SeBrs) were best synthesized using almond skin extract and optimized conditions of SeO2, ascorbic acid, pH, incubation temperature and time. Based on these results, the mechanism of SeBrs synthesis is proposed as having involved four stages such as nucleation, self-assembly, Ostwald ripening, and decomposition. Further, the test of antibacterial activity together with minimum inhibitory concentrations and minimum bactericidal concentrations indicated the selective, specific and good activity against B. subtilis. In addition, in situ coating of SeBrs on cotton fabric and its investigation by SEM demonstrated successful coating. Evident from plate-based assay and study of growth kinetics, coated fabric exhibited excellent anti-B. subtilis activity which demonstrated that biogenic SeBrs can be employed to coat cotton fabrics that can be used in operation theatres to reduce the episodes of Bacillus related Bacteraemia.

Selective interaction between phytomediated anionic silver nanoparticles and mercury leading to amalgam formation enables highly sensitive, colorimetric and memristor-based detection of mercury.

Presently, nanotechnology is being foreseen to play an important role in developing analytical assays for the detection of pollutants like mercury (Hg2+). In this study, Kokum fruit mediated silver nanoparticles (AgNPs) were differentially centrifuged to prepare anionic, monodispersed AgNPs to develop a highly sensitive, colorimetric and memristor-based assay for detection of Hg2+ in water samples. The investigation of the highly selective reaction between AgNPs and Hg2+ using HAADF-STEM images and EDS spectrum indicated the amalgam formation through etching and under potential deposition which resulted in a visible color change from brown to colorless, change in SPR intensity and also change in memristive switching like property of AgNPs. The developed colorimetric assay detected Hg2+ with a limit of detection (LOD) of 6.2 ppb and limit of quantification (LOQ) of 18.9 ppb and, quantitatively recovered Hg2+ with good accuracy and precision (RSD < 2%). Further, the test of memristive switching like property of AgNPs demonstrated frequency-dependent shrinkage of I-V hysteresis loop indicating memristive switching like property. The test of the sensitivity of Hg2+ detection was estimated to be 8.7 ppb as the LOD and 26.4 ppb as LOQ. Like the colorimetric assay, the memristor-based assay also recovered Hg2+ with good accuracy and precision.

Selective and sensitive colorimetric detection of platinum using Pseudomonas stutzeri mediated optimally synthesized antibacterial silver nanoparticles.

In this work, Pseudomonas stutzeri was used for the optimum biogenic synthesis of antibacterial silver nanoparticles (AgNPs) which were applied for colorimetric detection of platinum ions (Pt+2). The optimum synthesis conditions were 2 mM AgNO3, pH 9 and incubation at 60 °C for 24 h. The FTIR spectra indicated that biomolecules such as amino acids, proteins or enzymes from P. stutzeri were involved in the synthesis of AgNPs in the size range of 10-50 nm. Among the various metal ions tested and screened initially, the colloidal AgNPs probe-based colorimetric assay selectively detected Pt+2 with 50 ppm as the limit of detection (LOD). The assay demonstrated in the present study quantitatively recovered Pt+2 in the range of 70-150 % with good accuracy and precision. Further, the test of antibacterial activity of AgNPs alone, and in combination with ampicillin showed excellent activity against four of the six tested bacteria.

Immobilization of cellulase on iron tolerant Pseudomonas stutzeri biosynthesized photocatalytically active magnetic nanoparticles for increased thermal stability.

Bacteria mediated synthesis of magnetic nanoparticles (MNPs) for biotechnological applications is an important area of nanotechnology. This study demonstrates the use of iron tolerant bacterium for synthesis of MNPs for cellulase immobilization and photocatalytic activity. The enrichment, isolation, screening and molecular identification led to the selection of Pseudomonas stutzeri KDP_M2 with high degree of iron tolerance. The synthesis parameters such as 1 mM ferric quinate, pH 9 and 96 h static incubation were found optimum for maximum yield of 210 mg/L. The characterization using various techniques indicated that MNPs were Hematite (Fe2O3) with particle size between 10 and 20 nm. Further, vibrating sample magnetometer and thermogravimetric analyses demonstrated the superparamagnetic nature with high thermal stability. The MNPs were found an excellent support for immobilization of industrially important cellulase with 96.5% binding efficiency. The immobilization which was confirmed by Fourier transform infrared spectroscopy indicated that immobilization did not reduce the cellulase activity, rather enhanced the thermal stability and operational temperature range of cellulase. The immobilized cellulase showed maximum cellulolytic activity at pH 4.6 and retained 80% activity upto 3rd cycle of reuse, therefore, can be utilized repeatedly at acidic conditions.The monitoring the photocatalytic activity showed rapid degradation of methyl violet and methylene blue within initial 10 min. of reaction.