Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Co-Delivery of Nano-Silver and Vancomycin via Silica Nanopollens for Enhanced Antibacterial Functions

Infectious diseases caused by bacteria have led to a great threat to public health. With the significant advances in nanotechnology in recent decades, nanomaterials have emerged as a powerful tool to boost antibacterial performance due to either intrinsic bactericidal properties or by enhancing the delivery efficiency of antibiotics for effective pathogen killing. Vancomycin, as one of the most widely employed antimicrobial peptides, has a potent bactericidal activity, but at the same time shows a limited bioavailability. Silver nanoparticles have also been extensively explored and were found to have a well-recognized antibacterial activity and limited resistance potential; however, how to prevent nanosized Ag particles from aggregation in biological conditions is challenging. In this study, we aimed to combine the advantages of both vancomycin and nano-Ag for enhanced bacterial killing, where both antibacterial agents were successfully loaded onto a silica nanoparticle with a pollen-like morphology. The morphology of nano-Ag-decorated silica nanopollens was characterized using transmission electron microscopy and elemental mapping through energy dispersive spectroscopy. Silver nanoparticles with a size of 10–25 nm were observed as well-distributed on the surface of silica nanoparticles of around 200 nm. The unique design of a spiky morphology of silica nano-carriers promoted the adhesion of nanoparticles towards bacterial surfaces to promote localized drug release for bacterial killing, where the bacterial damage was visualized through scanning electron microscopy. Enhanced bactericidal activity was demonstrated through this co-delivery of vancomycin and nano-Ag, decreasing the minimum inhibition concentration (MIC) towards E. coli and S. epidermidis down to 15 and 10 µg/mL. This study provides an efficient antimicrobial nano-strategy to address potential bacterial infections

Ag-Coated Ternary Layered Double Hydroxide as a High-Performance SERS Sensor for Aldehydes

Volatile organic compounds (VOCs) are common environmental pollutants and important biomarkers for early diagnosis of lung cancer. However, aldehydes are difficult to detect directly due to their small Raman scattering cross-section and gaseous phase. Here, a Ag-coated ternary layered double hydroxide (LDH) was designed for the detection and identification of various aldehydes. The specific surface area of CoNi-LDH was increased by doping Fe3+, which provides abundant active sites to capture gas molecules. Furthermore, the energy band gap (Eg) was decreased due to the local amorphous FeCoNi-LDH with an extended band tail, promoting the excitonic transition of Fe0.07(CoNi)0.93-LDH. In addition, the Fermi level of Ag prevented the recombination of electron–hole pairs of Fe0.07(CoNi)0.93-LDH, providing a new bridge for charge transfer between the substrate and the molecule. Ag/Fe0.07(CoNi)0.93-LDH presented excellent surface-enhanced Raman scattering (SERS) performance for aldehyde VOCs by modification with 4-aminothiophenol (4-ATP) to capture aldehydes and realized the detection of benzaldehyde (BZA) at 10 ppb. The enhancement and Raman shift of the b2 mode indicated the contribution of chemical enhancement to the SERS system, so the substrate presented good uniformity. The recycling of the SERS substrate is realized based on the reversibility of the Schiff base reaction. These results manifested that Ag/FeCoNi-LDH has a wide prospect in the application in the trace detection of aldehydes

Evaluation of the Glaucomatous Macular Damage by Chromatic Pupillometry

Abstract Introduction This study aimed to examine the performance of binocular chromatic pupillometry for the objective and rapid detection of primary open-angle glaucoma (POAG), and to explore the association between pupillary light response (PLR) features and structural glaucomatous macular damage. Methods Forty-six patients (mean age 41.00 ± 13.03 years) with POAG and 23 healthy controls (mean age 42.00 ± 11.08 years) were enrolled. All participants underwent sequenced PLR tests of full-field, superior/inferior quadrant-field chromatic stimuli using a binocular head-mounted pupillometer. The constricting amplitude, velocity, and time to max constriction/dilation, and the post-illumination pupil response (PIPR) were analyzed. The inner retina thickness and volume measurements were determined by spectral domain optical coherence tomography. Results In the full-field stimulus experiment, time to pupil dilation was inversely correlated with perifoveal thickness (r = − 0.429, P < 0.001) and perifoveal volume (r = − 0.364, P < 0.001). Dilation time (AUC 0.833) showed good diagnostic performance, followed by the constriction amplitude (AUC 0.681) and PIPR (AUC 0.620). In the superior quadrant-field stimulus experiment, time of pupil dilation negatively correlated with inferior perifoveal thickness (r = − 0.451, P < 0.001) and inferior perifoveal volume (r = − 0.417, P < 0.001). The dilation time in response to the superior quadrant-field stimulus showed the best diagnostic performance (AUC 0.909). In the inferior quadrant-field stimulus experiment, time to pupil dilation (P < 0.001) correlated well with superior perifoveal thickness (r = − 0.299, P < 0.001) and superior perifoveal volume (r = − 0.304, P < 0.001). Conclusion The use of chromatic pupillometry offers a patient-friendly and objective approach to detect POAG, while the impairment of PLR features may serve as a potential indicator of structural macular damage