Emerging trends and future challenges of advanced 2D nanomaterials for combating bacterial resistance.

The number of multi-drug-resistant bacteria has increased over the last few decades, which has caused a detrimental impact on public health worldwide. In resolving antibiotic resistance development among different bacterial communities, new antimicrobial agents and nanoparticle-based strategies need to be designed foreseeing the slow discovery of new functioning antibiotics. Advanced research studies have revealed the significant disinfection potential of two-dimensional nanomaterials (2D NMs) to be severed as effective antibacterial agents due to their unique physicochemical properties. This review covers the current research progress of 2D NMs-based antibacterial strategies based on an inclusive explanation of 2D NMs' impact as antibacterial agents, including a detailed introduction to each possible well-known antibacterial mechanism. The impact of the physicochemical properties of 2D NMs on their antibacterial activities has been deliberated while explaining the toxic effects of 2D NMs and discussing their biomedical significance, dysbiosis, and cellular nanotoxicity. Adding to the challenges, we also discussed the major issues regarding the current quality and availability of nanotoxicity data. However, smart advancements are required to fabricate biocompatible 2D antibacterial NMs and exploit their potential to combat bacterial resistance clinically.

Multifunctional nucleoside-AIEgens bearing quaternary ammonium cationic for reversible response, bioimaging, and antibacterial.

A multifunctional nucleoside-based AIEgens sensor (TPEPy-dU) was constructed for visual screening of Hg2+, determine to the reversible response of Fe3+ and biothiols, and applied for cell imaging, and drug-free bacterial killing. The TPEPy-dU displayed 10-folds fluorescence enhancement at 540 nm of emission in response to trace Hg2+ ions with 10 nM of LOD, which can be immediately quenched by adding Fe3+ or GSH/Cys-containing sulfhydryl groups. Moreover, their bacterial staining efficiency closely correlates with their antibacterial efficacy as they demonstrated comparatively higher antibacterial activity against Gram-positive bacteria than Gram-negative bacteria. The drug-free antibacterial results involved the stating prominent surface damages at the sites of interactions between bacterial cells and TPEPy-dU that were further verified by CLSM and SEM images. It can be applied as a potential fluorescent agent to explore the related antibacterial mechanisms for treating and monitoring bacterial infections in vivo due to their nontoxic nature. Compared with conventional sensors and antibacterial therapies, these findings elevated the synthetic strategies of fluorescent probes and represented an advanced antibacterial agent wearing quaternary ammonium cationic with low resistance in clinical diagnosis.

Copper-based nanoparticles against microbial infections.

Drug-resistant bacteria and highly infectious viruses are among the major global threats affecting the human health. There is an immediate need for novel strategies to tackle this challenge. Copper-based nanoparticles (CBNPs) have exhibited a broad antimicrobial capacity and are receiving increasing attention in this context. In this review, we describe the functionalization of CBNPs, elucidate their antibacterial and antiviral activity as well as applications, and briefly review their toxicity, biodistribution, and persistence. The limitations of the current study and potential solutions are also shortly discussed. The review will guide the rational design of functional nanomaterials for antimicrobial application. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Defect-rich graphene-coated metamaterial device for pesticide sensing in rice.

Performing sensitive and selective detection in a mixture is challenging for terahertz (THz) sensors. In light of this, many methods have been developed to detect molecules in complex samples using THz technology. Here we demonstrate a defect-rich monolayer graphene-coated metamaterial operating in the THz regime for pesticide sensing in a mixture through strong local interactions between graphene and external molecules. The monolayer graphene induces a 50% change in the resonant peak excited by the metamaterial absorber that could be easily distinguished by THz imaging. We experimentally show that the Fermi level of the graphene can be tuned by the addition of molecules, which agrees well with our simulation results. Taking chlorpyrifos methyl in the lixivium of rice as a sample, we further show the molecular sensing potential of this device, regardless of whether the target is in a mixture or not.

Induced Autophagy of Macrophages and the Regulation of Inflammatory Effects by Perovskite Nanomaterial LaNiO3.

Perovskite nanomaterials (NMs) possess excellent physicochemical properties and have promising applications in light-emitting diodes (LEDs), lasers, photodetectors, and artificial synapse electronics. Potential exposure to these NMs happens in the manufacture and application of the perovskite-based products, however, the biological safety of these NMs is still unknown. Here, we used the LaNiO3 NM (LNO), a typical kind of perovskite nanostructures to study the interaction with macrophages (J774A.1) and to explore its biological effects at the cellular level. Firstly, we characterized the properties of LNO including the size, shape, and crystal structure using Transmission electronic microscope (TEM), Dynamic lighting scattering (DLS), and X-ray diffraction (XRD). Secondly, to gain a better understanding of the biological effect, we evaluated the effect of LNO on cell viability and found that LNO induced cell autophagy at a concentration of 5 µg/ml and influenced the inflammatory response based on RT-PCR result. Finally, we demonstrated the mechanism that LNO causes cell autophagy and immune response is probably due to the metal ions released from LNO in acidic lysosomes, which triggered ROS and increased lysosomal membrane permeation. This study indicates the safety aspect of perovskite NMs and may guide the rational design of perovskite NMs with more biocompatibility during their manufacture and application.

Shape-dependent significant physical mutilation and antibacterial mechanisms of gold nanoparticles against foodborne bacterial pathogens (Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus) at lower concentrations.

Gold nanoparticles (AuNPs) have been reported for their most desirable properties as compared to any other noble metal-based nanoparticles, which wider their applications in various fields including catalysis, bio-imaging, biosensors, medicine, biology, and material chemistry. In this study, the shape-dependent antibacterial activity of AuNPs: nanospheres (AuNSps), nanostars (AuNSts), and nanocubes (AuNCs) were investigated against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus at lower concentrations. The optical, crystallographic and morphological characterization of AuNPs was analyzed by UV-visible spectroscopy, X-ray diffraction spectroscopy, and transmission electron microscopy (TEM). Shape-dependent antibacterial qualitative and quantitative analyses revealed an effective bactericidal activity of AuNCs against the tested bacteria, followed by AuNSps and AuNSts. The study revealed that the AuNCs are effective bactericidal agents with 100% inactivation rate. The visual analysis confirmed the antibacterial activity of AuNCs and AuNSps by showing physical mutilated bacterial cells which involved cell loss, loosening of the cell wall, loss of flagella and cellular matrix. Finally, released nucleic acid was measured for the treated bacterial cells which support the physical mutilation by releasing 38 µg/mL (Pseudomonas aeruginosa) of cellular material after treating with AuNCs. It is concluded from this study that AuNPs showed the significant antibacterial property at lower concentrations. More applications can be explored including anti-infections, decontamination, and food safety.

Temperature-dependent terahertz vibrational spectra of tetracycline and its degradation products.

Terahertz (THz) spectroscopy has emerged as an attractive technique for qualitative and quantitative detection. Analysis of these chemicals in the THz range under various temperatures can yield detailed information on molecular vibrational modes, which is of utmost importance for effective detection. Here we report the use of THz time-domain spectroscopy (THz-TDS) to measure tetracyclines hydrochloride (TCH) and its degradation products including epitetracycline hydrochloride (ETCH), anhydrotetracycline hydrochloride (ATCH), and epianhydrotetracycline hydrochloride (EATCH) over the temperature range of 4.5-300 K for the first time. The results showed that these four tetracyclines exhibited numerous distinct spectral features in frequency-dependent absorption spectra, which demonstrated the qualitative capacity of THz-TDS. Through density functional theory (DFT) calculations and analysis of temperature-dependent absorption spectra, the origin of the observed terahertz absorption peaks of these four tetracyclines were well interpreted. This study could lay the foundation for high-performance analysis of biological and chemical molecules by THz spectroscopy, which is essential for sensing application.

Genetic diversity analysis of Bemisia tabaci populations in Pakistan using RAPD markers

Background: The Bemisia tabaci is one of the most devastating pests of agricultural crops and ornamental plants worldwide. The genetic diversity and biotype status of the Bemisia tabaci in Pakistan was assessed by using random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). A total 80 samples of B. tabaci collected from 14 districts of the Punjab province and 7 districts of the Sindh province were included. Results: All 10 primers screened in this study generated 151 scorable amplification products, of which 117 or 77 percent were polymorphic. Pairwise Nei and Li’s similarity had ranged from 0.25 to 0.88 among all individuals analyzed. Based on Nei and Li’s similarity coefficients Bemisia populations were grouped into 3 main clusters and clearly distinguished the non B biotype from the B biotype. Conclusion: The level of similarity among populations of same biotypes was high whereas between populations of non B and B biotypes appeared to be less closely related. This analysis showed that non B biotype is prevalent in both provinces however B biotype is restricted to few locations in Sindh. This monitoring of the spread of B. tabaci in Pakistan will assist in the establishment of appropriate management strategies.

Characterization of an A-kinase anchor protein in equine spermatozoa and examination of the effect of semen cooling and cryopreservation on the binding of that protein to the regulatory subunit of protein kinase-A.

OBJECTIVE: To determine whether a homologue of A-kinase anchor protein 4 (AKAP4) is present and functional as an AKAP in equine spermatozoa and examine the effect of semen cooling and cryopreservation on binding of equine AKAP4 to the regulatory (RII) subunit of protein kinase-A (PK-A). SAMPLE POPULATION: Ejaculated semen collected from 2 fertile stallions, 3 bulls, and 3 humans. PROCEDURE: Identification of an equine homologue of AKAP4 was investigated via DNA sequencing. Protein was extracted from the spermatozoa of each species for immunoblot analysis to identify AKAP4 and its precursor protein, pro-AKAP4; immunofluorescence microscopy was used to localize those proteins in spermatozoa. Ligand overlay assays were used to determine whether the identified proteins bound to the RII subunit of PK-A and whether cooling or cryopreservation of spermatozoa affected that binding. RESULTS: The partial genomic sequence of AKAP4 was identified in equine spermatozoa, and immunoblot analysis confirmed that AKAP4 and pro-AKAP4 are present in equine spermatozoa. Via immunofluorescence microscopy, these proteins were localized to the spermatozoal principal piece. Results of ligand overlay assays indicated that equine AKAP4 and pro-AKAP4 bind to the RII subunit of PK-A and are AKAPs; AKAP4-RII binding was not affected by cooling or cryopreservation of spermatozoa. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that equine AKAP4 anchors PK-A to the spermatozoal flagellum (where the kinase is likely to be required for the regulation of spermatozoal motility), but decreases in spermatozoal motility in cooled or cryopreserved semen are not associated with decreased binding of AKAP4 and PK-A.

Differential ubiquitination of stallion sperm proteins: possible implications for infertility and reproductive seasonality.

Antibodies against ubiquitin, a universal proteolytic marker, show increased cross-reactivity with defective spermatozoa in men and bulls. We investigated sperm ubiquitination in the stallion, a seasonally polyestrous mammal. Immunofluorescence and immunoelectron microscopy demonstrated that anti-ubiquitin antibodies bind to the surface of both membrane-intact and aldehyde-fixed spermatozoa. Cross-reactivity to the ubiquitin-conjugating enzyme E2 was also detected in sperm. Immunohistochemistry showed that ubiquitinated spermatozoa were first detected in the caput epididymis, coincident with a strong accumulation of ubiquitin and ubiquitin C-terminal hydrolase, protein gene product 9.5, in the apical stereocilia of the epididymal epithelium. Testicular spermatozoa did not display significant ubiquitin cross-reactivity. Similarly, lesser accumulation of ubiquitin cross-reactive substrates was identified in the accessory sex glands. Semen samples were collected from three fertile stallions and one subfertile stallion between December and February and probed for ubiquitin by flow cytometry and immunoblotting. Flow cytometric analysis showed that sperm from the subfertile stallion had higher ubiquitin levels than sperm from the other three stallions. In addition, immunoblot analysis of sperm proteins from the subfertile stallion showed two unique ubiquitin cross-reactive bands that were not present in sperm extracts from the three fertile stallions. To screen for a possible role for ubiquitin in seasonal changes in sperm production, semen samples from two fertile stallions were collected in March, June, September, and December and subjected to a flow cytometric ubiquitin assay. The lowest levels of ubiquitin-labeled sperm were found in March, approximately coincident with the onset of the natural horse breeding season. A progressive increase in sperm ubiquitin levels was found during summer and fall, with a peak in December. These data suggest that stallion sperm are differentially ubiquitinated during epididymal maturation and that this ubiquitination may reflect changes in sperm numbers and semen quality. The association between changes in sperm ubiquitination and seasonal changes in sperm production will be subjected to further studies in a larger cohort of animals.