Fabrication of low cost highly structured silver capped aluminium nanorods as SERS substrate for the detection of biological pathogens.

We report the fabrication of low cost highly structured silver (Ag) capped aluminium (Al) nanorods (NRs) as surface enhanced Raman spectroscopy (SERS) substrate utilising the glancing angle deposition technique. The nano-capping of silver onto the Al NRs can concentrate the local electric field within the minimal volume that can serve as hotspots. The average size of the Ag nanocaps was 50 nm. The newly proposed nanoporous Ag capped Al NRs as SERS substrate could detect the Raman signal of rhodamine 6G (R6G) up to 10-15molar concentration. The significant enhancement in the Raman signal of 107was achieved for Ag capped Al NRs considering R6G as a probe molecule. Using the developed SERS substrate, we recorded Raman spectra forEscherichia colibacteria with its concentration varying from 108colony forming units per ml (CFU ml-1) up to 102CFU ml-1. All the reported Raman spectra were acquired by a portable handheld Raman spectrometer. Hence, this newly proposed low cost, effective SERS substrate can be used commercially for the onsite detection of clinical pathogens. The 3D finite difference time domain simulation model was performed for Ag capped Al nanostructure to understand the generation of hotspots. The simulated results show excellent agreement with the experimental results. We fabricated uncapped Ag nanorods of similar dimensions and performed the experimental measurements and simulations for comparison. We found a significant enhancement in Ag capped Al NRs compared to the long Ag NRs. The description of the Raman signal enhancement has been elaborated.

Plasmonic nano-bowls for monitoring intra-membrane changes in liposomes, and DNA-based nanocarriers in suspension.

Programmable nanoscale carriers, such as liposomes and DNA, are readily being explored for personalized medicine or disease prediction and diagnostics. The characterization of these nanocarriers is limited and challenging due to their complex chemical composition. Here, we demonstrate the utilization of surface-enhanced Raman spectroscopy (SERS), which provides a unique molecular fingerprint of the analytes while reducing the detection limit. In this paper, we utilize a silver coated nano-bowl shaped polydimethylsiloxane (PDMS) SERS substrate. The utilization of nano-bowl surface topology enabled the passive trapping of particles by reducing mobility, which results in reproducible SERS signal enhancement. The biological nanoparticles' dwell time in the nano-trap was in the order of minutes, thus allowing SERS spectra to remain in their natural aqueous medium without the need for drying. First, the geometry of the nano-traps was designed considering nanosized bioparticles of 50-150 nm diameter. Further, the systematic investigation of maximum SERS activity was performed using rhodamine 6 G as a probe molecule. The potential of the optimized SERS nano-bowl is shown through distinct spectral features following surface- (polyethylene glycol) and bilayer- (cholesterol) modification of empty liposomes of around 140 nm diameter. Apart from liposomes, the characterization of the highly crosslinked DNA specimens of only 60 nm in diameter was performed. The modification of DNA gel by liposome coating exhibited unique signatures for nitrogenous bases, sugar, and phosphate groups. Further, the unique sensitivity of the proposed SERS substrate displayed distinct spectral signatures for DNA micelles and drug-loaded DNA micelles, carrying valuable information to monitor drug release. In conclusion, the findings of the spectral signatures of a wide range of molecular complexes and chemical morphology of intra-membranes in their natural state highlight the possibilities of using SERS as a sensitive and instantaneous characterization alternative.

SERS Nanowire Chip and Machine Learning-Enabled Classification of Wild-Type and Antibiotic-Resistant Bacteria at Species and Strain Levels.

Antimicrobial resistance (AMR) is a major health threat worldwide and the culture-based bacterial detection methods are slow. Surface-enhanced Raman spectroscopy (SERS) can be used to identify target analytes in real time with sensitivity down to the single-molecule level, providing a promising solution for the culture-free bacterial detection. We report the fabrication of SERS substrates having tightly packed silver (Ag) nanoparticles loaded onto long silicon nanowires (Si NWs) grown by the metal-assisted chemical etching (MACE) method for the detection of bacteria. The optimized SERS chips exhibited sensitivity down to 10-12 M concentration of R6G molecules and detected reproducible Raman spectra of bacteria down to a concentration of 100 colony forming units (CFU)/mL, which is a thousand times lower than the clinical threshold of bacterial infections like UTI (105 CFU/mL). A Siamese neural network model was used to classify SERS spectra from bacteria specimens. The trained model identified 12 different bacterial species, including those which are causative agents for tuberculosis and urinary tract infection (UTI). Next, the SERS chips and another Siamese neural network model were used to differentiate AMR strains from susceptible strains of Escherichia coli (E. coli). The enhancement offered by SERS chip-enabled acquisitions of Raman spectra of bacteria directly in the synthetic urine by spiking the sample with only 103 CFU/mL E. coli. Thus, the present study lays the ground for the identification and quantification of bacteria on SERS chips, thereby offering a potential future use for rapid, reproducible, label-free, and low limit detection of clinical pathogens.

Luminescence studies in cadmium telluride nanocrystals grown on glass substrates.

The thermal evaporation method can easily be employed to fabricate hybrid inorganic-organic LEDs and the emission properties can be controlled by varying the thickness of the nanocrystalline CdTe film. The fabrication of CdTe nanocrystals on glass substrates was demonstrated using a thermal evaporation method. Films were characterised using various experimental tools, such as SEM, TEM, AFM, UV-Vis and PL spectroscopy. The formation of nanoparticles with diameters from 1.5 nm up to 9 nm was observed in the nanocrystalline thin films. The organic light emitting diodes (OLEDs) based on these nanocrystals as an emissive layer exhibit electroluminescence (EL) in the green to yellow region of the visible spectrum, which is ascribed to the varying size dependent EL from the nanocrystals of CdTe present in the thin film. The method demonstrates an easy and convenient way to incorporate inorganic CdTe nanocrystals inside the organic light emitting devices.

Unveiling Uncommon Manifestations in a Pediatric Patient With Systemic Lupus Erythematosus: A Case Report.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with multi-organ involvement. It may involve skin, kidneys, joints, central nervous system (CNS), and cardiopulmonary system. Marked variations in clinical presentations are seen in SLE patients, ranging from subclinical to life-threatening manifestations. SLE and antiphospholipid syndrome (APS) may be associated with Libman-Sacks endocarditis. Visceral vasculitis usually manifests with disease flares and can affect almost any organ. APS can have arterial or venous thrombosis and the presence of persistently positive antiphospholipid antibodies (aPL), including lupus anticoagulants (LA), anticardiolipin antibodies (aCL), and/or anti-ß2-glycoprotein-I antibodies (aß2GPI). Peripheral neuropathy is unusual in pediatric patients. We present a case of an adolescent girl with juvenile SLE (JSLE) in whom endocarditis and digital gangrene at first presentation were actually masquerading underlying life-threatening secondary APS with extensive medium vessel thrombosis. Additionally, there was cutaneous and visceral vasculitis and a rare peripheral nervous system (PNS) manifestation, mononeuritis multiplex (MNM).