Layer-by-layer thin films of Ti3C2 MXene and gold nanoparticles as an ideal SERS platform

The combination of plasmonic metals and MXene, as a new and interesting member of the 2D material class, may provide unique advantages in terms of low cost, versatility, flexibility, and improved activity as an ideal surface-enhanced Raman spectroscopy (SERS) platform. Despite the recent progress, the present studies on the utilization of plasmonic metal/MXene-based SERS systems are quite limited and thereby benefits of the extraordinary properties of this combination cannot be realized. In this study, for the first time, we propose layer-by-layer (LbL) thin films of Ti3C2 MXene and gold nanoparticles (AuNPs) as a robust SERS platform (Ti3C2/AuNPs). For this, Ti3C2 MXene was synthesized from the Ti3AlC2 MAX phase, and the Ti3C2/AuNP LbL film was fabricated via a vacuum-assisted filtration method to create consecutive layers of each material. This procedure produced densely distributed AuNPs in the LbL film in a well-controlled manner. The SERS activity tests for methylene blue and DTNB as Raman reporter molecules showed that they exhibited enhancement factors of 1.5 × 106 and 1.2 × 106 and limits of detection of 1 × 10-8 M, and 2.5 × 10-8 M, respectively. Various mechanisms, including the formation of hotspots due to AuNPs on the interlayer of Ti3C2, improved surface roughness and resultant optical activity, as well as the synergistic effect between Ti3C2 and AuNPs, contributed to the resultant SERS activity to some extent. This study has proven the feasibility of the Ti3C2/AuNP LbL system as a robust SERS-based sensor platform, paving the way for its use in various biological and chemical applications.

Machine Learning-Assisted SERS Reveals the Biochemical Signature of Enhanced Protein Secretion from Surface-Modified Magnetic Nanoparticles

This study introduces a novel investigation of the interaction between Komagataella phaffii cells and iron oxide-based magnetic nanoparticles (Fe3O4 MNPs) via protein secretion and machine learning (ML)-assisted surface-enhanced Raman scattering (SERS). For the first time, we produced Fe3O4, Fe3O4@PEG, Fe3O4@PEI10kDa, and Fe3O4@PEI25kDa MNPs by a one-pot coprecipitation reaction. The addition of polymers to the reaction conditions significantly affected the shape, surface charge, size, and size distribution of the MNPs. The surface modification of MNPs is effectively accomplished using polyethylenimine (PEI), and the ζ-potential values of the MNPs exceed +25 mV under the NH4OH control. The homogeneity of MNPs synthesized with NH4OH is more pronounced according to transmission electron microscopy (TEM) pictures. All MNPs exhibited excellent immobilization efficiency (>92%) when we used 250 ppm Fe-containing MNP solutions. Smaller MNPs uniformly encapsulated the surface of K. phaffii cells, whereas larger MNPs exhibited irregular accumulation. K. phaffii cells exhibited excellent viability in all MNP solutions at up to 1000 ppm of Fe concentrations. Finally, the highest recombinant azurin protein secretion rate was obtained in Fe3O4@PEI10kDa MNP-immobilized cells (about 1.3 times). The ML-assisted SERS analysis revealed that MNP interactions with K. phaffii cells were mediated by proteins such as mannoproteins and membrane transporter proteins as well as N-acetylglucosamine (i.e., chitin). These findings revealed the effect of the size and surface properties of MNPs on the immobilization of K. phaffii cells and the enormous potential of magnetic immobilization for protein secretion.

Machine learning-assisted SERS approach enables the biochemical discrimination in Bcl-2 and Mcl-1 expressing yeast cells treated with ketoconazole and fluconazole antifungals

Antifungal medications are important due to their potential application in cancer treatment either on their own or with traditional treatments. The mechanisms that prevent the effects of these medications and restrict their usage in cancer treatment are not completely understood. The evaluation and discrimination of the possible protective effects of the anti-apoptotic members of the Bcl-2 family of proteins, critical regulators of mitochondrial apoptosis, against antifungal drug-induced cell death has still scientific uncertainties that must be considered. Novel, simple, and reliable strategies are highly demanded to identify the biochemical signature of this phenomenon. However, the complex nature of cells poses challenges for the analysis of cellular biochemical changes or classification. In this study, for the first time, we investigated the probable protective activities of Bcl-2 and Mcl-1 proteins against cell damage induced by ketoconazole (KET) and fluconazole (FLU) antifungal drugs in a yeast model through surface-enhanced Raman spectroscopy (SERS) approach. The proposed SERS platform created robust Raman spectra with a high signal-to-noise ratio. The analysis of SERS spectral data via advanced unsupervised and supervised machine learning methods enabled unquestionable differentiation (100 %) in samples and biomolecular identification. Various SERS bands related to lipids and proteins observed in the analyses suggest that the expression of these anti-apoptotic proteins reduces oxidative biomolecule damage induced by the antifungals. Also, cell viability assay, Annexin V-FITC/PI double staining, and total oxidant and antioxidant status analyses were performed to support Raman measurements. We strongly believe that the proposed approach paves the way for the evaluation of various biochemical structures/changes in various cells.

Inflammaging in Multidrug-Resistant Sepsis of Geriatric ICU Patients and Healthcare Challenges

Multidrug-resistant sepsis (MDR) is a pressing concern in intensive care unit (ICU) settings, specifically among geriatric patients who experience age-related immune system changes and comorbidities. The aim of this review is to explore the clinical impact of MDR sepsis in geriatric ICU patients and shed light on healthcare challenges associated with its management. We conducted a comprehensive literature search using the National Center for Biotechnology Information (NCBI) and Google Scholar search engines. Our search incorporated keywords such as "multidrug-resistant sepsis" OR "MDR sepsis", "geriatric ICU patients" OR "elderly ICU patients", and "complications", "healthcare burdens", "diagnostic challenges", and "healthcare challenges" associated with MDR sepsis in "ICU patients" and "geriatric/elderly ICU patients". This review explores the specific risk factors contributing to MDR sepsis, the complexities of diagnostic challenges, and the healthcare burden faced by elderly ICU patients. Notably, the elderly population bears a higher burden of MDR sepsis (57.5%), influenced by various factors, including comorbidities, immunosuppression, age-related immune changes, and resource-limited ICU settings. Furthermore, sepsis imposes a significant economic burden on healthcare systems, with annual costs exceeding $27 billion in the USA. These findings underscore the urgency of addressing MDR sepsis in geriatric ICU patients and the need for tailored interventions to improve outcomes and reduce healthcare costs.

Controlling the Evolution of Selective Vancomycin Resistance through Successful Ophthalmic Eye-Drop Preparation of Vancomycin-Loaded Nanoliposomes Using the Active-Loading Method

Vancomycin is the front-line defense and drug of choice for the most serious and life-threatening methicillin-resistant Staphylococcus aureus (MRSA) infections. However, poor vancomycin therapeutic practice limits its use, and there is a consequent rise of the threat of vancomycin resistance by complete loss of its antibacterial activity. Nanovesicles as a drug-delivery platform, with their featured capabilities of targeted delivery and cell penetration, are a promising strategy to resolve the shortcomings of vancomycin therapy. However, vancomycin's physicochemical properties challenge its effective loading. In this study, we used the ammonium sulfate gradient method to enhance vancomycin loading into liposomes. Depending on the pH difference between the extraliposomal vancomycin-Tris buffer solution (pH 9) and the intraliposomal ammonium sulfate solution (pH 5-6), vancomycin was actively and successfully loaded into liposomes (up to 65% entrapment efficiency), while the liposomal size was maintained at 155 nm. Vancomycin-loaded nanoliposomes effectively enhanced the bactericidal effect of vancomycin; the minimum inhibitory concentration (MIC) value for MRSA decreased 4.6-fold. Furthermore, they effectively inhibited and killed heteroresistant vancomycin-intermediate S.aureous (h-VISA) with an MIC of 0.338 μg mL^-1. Moreover, MRSA could not develop resistance against vancomycin that was loaded into and delivered by liposomes. Vancomycin-loaded nanoliposomes could be a feasible solution for enhancing vancomycin's therapeutic use and controlling the emerging vancomycin resistance.

Advances in surface-enhanced Raman spectroscopy technology for detection of foodborne pathogens

Rapid control and prevention of diseases caused by foodborne pathogens is one of the existing food safety regulatory issues faced by various countries and has received wide attention from all sectors of society. The development of rapid and reliable detection methods for foodborne pathogens remains a hot research area for food safety and public health because of the limitations of complex steps, time-consuming, low sensitivity, or poor selectivity of commonly used methods. Surface-enhanced Raman spectroscopy (SERS), as a novel spectroscopic technique, has the advantages of high sensitivity, selectivity, rapid and nondestructive detection and has exhibited broad application prospects in the determination of pathogenic bacteria. In this study, the enhancement mechanisms of SERS are briefly introduced, then the characteristics and properties of liquid-phase, rigid solid-phase, and flexible solid-phase are categorized. Furthermore, a comprehensive review of the advances in label-free or label-based SERS strategies and SERS-compatible techniques for the detection of foodborne pathogens is provided, and the advantages and disadvantages of these methods are reviewed. Finally, the current challenges of SERS technology applied in practical applications are listed, and the possible development trends of SERS in the field of foodborne pathogens detection in the future are discussed.

Fast Track Diagnostic Tools for Clinical Management of Sepsis: Paradigm Shift from Conventional to Advanced Methods

Sepsis is one of the deadliest disorders in the new century due to specific limitations in early and differential diagnosis. Moreover, antimicrobial resistance (AMR) is becoming the dominant threat to human health globally. The only way to encounter the spread and emergence of AMR is through the active detection and identification of the pathogen along with the quantification of resistance. For better management of such disease, there is an essential requirement to approach many suitable diagnostic techniques for the proper administration of antibiotics and elimination of these infectious diseases. The current method employed for the diagnosis of sepsis relies on the conventional culture of blood suspected infection. However, this method is more time consuming and generates results that are false negative in the case of antibiotic pretreated samples as well as slow-growing microbes. In comparison to the conventional method, modern methods are capable of analyzing blood samples, obtaining accurate results from the suspicious patient of sepsis, and giving all the necessary information to identify the pathogens as well as AMR in a short period. The present review is intended to highlight the culture shift from conventional to modern and advanced technologies including their limitations for the proper and prompt diagnosing of bloodstream infections and AMR detection.

Catalytic and SERS activities of WO3-based nanowires: the effect of oxygen vacancies, silver nanoparticle doping, and the type of organic dye

Oxygen vacancies in tungsten trioxide (WO₃) nanostructures (WO_3-x) dominate the major characteristics of the material and determine their activity in various applications including photocatalysis and surface-enhanced Raman spectroscopy (SERS). Despite some studies performed in the last decade, the photocatalytic activity toward different pollutants and SERS activity toward different Raman reporter molecules are still unclear and may provide valuable insights into this research field. Therefore, in this study, we propose WO_3-x nanowires (NWs) both as ideal photocatalysts for the degradation of organic pollutants such as crystal violet (CV), methylene blue (MB), malachite green (MG), and rhodamine 6G (R6G) and a SERS platform for the detection of these molecules. In the first step, WO_3-x NWs were fabricated through the solvothermal method. Afterward, the oxygen vacancy content of WO_3-x NWs was manipulated by the addition of silver ions or H₂O₂. Although H₂O₂ led to a remarkable decrease in oxygen vacancies (WO₃), the addition of silver ions led to the formation of Ag nanostructures on WO_3-x NWs (WO_3-x@Ag). Interestingly, the combination of WO_3-x and WO_3-x@Ag nanosystems with all dye molecules resulted in the formation of H-aggregates due to the strong electrostatic interaction between the nanostructure and dye molecules and then its photocatalytic degradation, while regular degradation of dyes was observed for WO₃. In SERS activity tests, each NP system exhibited different activities depending on various parameters including the chemical nature of the nanosystem, the degree of oxygen vacancy, the interaction of the Raman reporter molecule with the surface of the NP, and the resultant formation of H-aggregates or photocatalytic degradation. The combination of MB with WO_3-x, WO_3-x@Ag, and WO₃ created enhancement factors such as 1.6 × 10³, 5.4 × 10³, and 6.2 × 10³, respectively. This report showed that the parameters mentioned here must be considered in detail to evaluate the photocatalytic and SERS activity of the WO₃-based nanosystem.

Bio-Receptors Functionalized Nanoparticles: A Resourceful Sensing and Colorimetric Detection Tool for Pathogenic Bacteria and Microbial Biomolecules

Pathogenic bacteria and several biomolecules produced by cells and living organisms are common biological components posing a harmful threat to global health. Several studies have devised methods for the detection of varying pathogenic bacteria and biomolecules in different settings such as food, water, soil, among others. Some of the detection studies highlighting target pathogenic bacteria and biomolecules, mechanisms of detection, colorimetric outputs, and detection limits have been summarized in this review. In the last 2 decades, studies have harnessed various nanotechnology-based methods for the detection of pathogenic bacteria and biomolecules with much attention on functionalization techniques. This review considers the detection mechanisms, colorimetric prowess of bio-receptors and compares the reported detection efficiency for some bio-receptor functionalized nanoparticles. Some studies reported visual, rapid, and high-intensity colorimetric detection of pathogenic bacteria and biomolecules at a very low concentration of the analyte. Other studies reported slight colorimetric detection only with a large concentration of an analyte. The effectiveness of bio-receptor functionalized nanoparticles as detection component varies depending on their selectivity, specificity, and the binding interaction exhibited by nanoparticles, bio-receptor, and analytes to form a bio-sensing complex. It is however important to note that the colorimetric properties of some bio-receptor functionalized nanoparticles have shown strong and brilliant potential for real-time and visual-aided diagnostic results, not only to assess food and water quality but also for environmental monitoring of pathogenic bacteria and a wide array of biomolecules.

Fluorescence labelled XT5 modified nano-capsules enable highly sensitive myeloma cells detection

Accurate diagnosis of cancer cells in early stages plays an important role in reliable therapeutic strategies. In this study, we aimed to develop fluorescence-conjugated polymer carrying nanocapsules (NCs) which is highly selective for myeloma cancer cells. To gain specific targeting properties, NCs, XT5 molecules (a benzamide derivative) which shows high affinity properties against protease-activated receptor-1 (PAR1), that overexpressed in myeloma cancer cells, was used. For this purpose, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[carboxy(polyethylene glycol)-2000]-carboxylic acid (DSPE-PEG₂₀₀₀-COOH) molecules, as a main encapsulation material, was conjugated to XT5 molecules due to esterification reaction using N,N'-dicyclohexylcarbodiimide as a coupling agent. The synthesized DSPE-PEG₂₀₀₀-COO-XT5 was characterized by using FT-IR and¹H NMR spectroscopies and results indicated that XT5 molecules were successfully conjugated to DSPE-PEG₂₀₀₀-COOH. Poly(fluorene-alt-benzothiadiazole) (PFBT) conjugated polymer (CP) was encapsulated with DSPE-PEG₂₀₀₀-COO-XT5 due to dissolving in tetrahydrofuran and ultra-sonication in an aqueous solution, respectively. The morphological properties, UV-vis absorbance, and emission properties of obtainedCPencapsulatedDSPE-PEG₂₀₀₀-COO-XT5(CPDP-XT5) NCs was determined by utilizing scanning electron microscopy, UV-vis spectroscopy, and fluorescent spectroscopy, respectively. Cytotoxicity properties of CPDP-XT5 was evaluated by performing MTT assay on RPMI 8226 myeloma cell lines. Cell viability results confirmed that XT5 molecules were successfully conjugated to DSPE-PEG₂₀₀₀-COOH. Specific targeting properties of CPDP-XT5 NCs and XT5-free NCs (CPDP NCs) were investigated on RPMI 8226 myeloma cell lines by utilizing fluorescent microscopy and results indicated that CPDP-XT5 NCs shows significantly high affinity in comparison to CPDP NCs against the cells. Homology modeling and molecular docking properties of XT5 molecules were evaluated and simulation results confirmed our results.

Rapid identification of the resistance of urinary tract pathogenic bacteria using deep learning-based spectroscopic analysis

The resistance of urinary tract pathogenic bacteria to various antibiotics is increasing, which requires the rapid detection of infectious pathogens for accurate and timely antibiotic treatment. Here, we propose a rapid diagnosis strategy for the antibiotic resistance of bacteria in urinary tract infections (UTIs) based on surface-enhanced Raman scattering (SERS) using a positively charged gold nanoparticle planar solid SERS substrate. Then, an intelligent identification model for SERS spectra based on the deep learning technique is constructed to realize the rapid, ultrasensitive, and non-labeled detection of pathogenic bacteria. A total of 54,000 SERS spectra were collected from 18 isolates belonging to 6 species of common UTI bacteria in this work to realize identification of bacterial species, antibiotic sensitivity, and multidrug resistance (MDR) via convolutional neural networks (CNN). This method significantly simplify the Raman data processing processes without background removing and smoothing, however, achieving 96% above classification accuracy, which was significantly greater than the 85% accuracy of the traditional multivariate statistical analysis algorithm principal component analysis combined with the K-nearest neighbor (PCA-KNN). This work clearly elucidated the potential of combining SERS and deep learning technique to realize culture-free identification of pathogenic bacteria and their associated antibiotic sensitivity.

Electrochemical-based ''antibiotsensor'' for the whole-cell detection of the vancomycin-susceptible bacteria

In this study, we aim to develop an antibiotic-based biosensor platform 'Antibiotsensor' for the specific detection of gram-positive bacteria using vancomycin modified Screen Printed Gold Electrodes (SPGEs). Through this pathway, vancomycin molecules were first functionalized with thiol groups and characterized with quadrupole time of flight (q-TOF) mass spectroscopy analysis. Immobilization of thiolated vancomycin molecules (HS-Van) onto SPGEs was carried out based on self-assembled monolayer (SAM) phenomenon. Electrochemical impedance spectroscopy (EIS) was employed to test the detection and showed a considerable change in impedance value upon the binding of HS-Van molecules onto the electrode surface. Atomic Force Microscopy analysis indicated that SPGE was successfully modified upon the treatment with HS-Van molecules based on the shift in surface roughness from 173 ± 2 nm to 301 ± 3 nm. Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy proved the EIS and AFM results as well by showing characteristic peaks of immobilized HS-Van molecule. As a proof-of-concept, EIS-based susceptibility testing was performed using Escherichia coli, Staphylococcus aureus and Mycobacterium smegmatis bacteria to prove the specificity of obtained SPGE-Van. EIS data showed that the charge transfer resistance (R_ct) values changed from 1.08, 1.18 to 26.5, respectively, indicating that vancomycin susceptible S. aureus was successfully attached onto SPGE-Van surface strongly, while vancomycin resistance E. coli and M. smegmatis did not show any significant attachment properties. In addition, different concentration (10⁸-10 CFU/mL) of S. aureus was performed to investigate sensitivity of proposed sensor platform. Limit of detection and limit of quantitation was calculated as 10^1.58 and 10^4.81 CFU/mL, respectively. Scanning electron microscopy (SEM) analysis also confirmed that only S. aureus bacteria was attached to the surface in a dense monolayer distribution. We believe that the proposed approach is selective and sensitive towards the whole-cell detection of vancomycin-susceptible bacteria and can be modified for different purposes in the future.