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1. Continuous, Nondestructive Detection of Microorganism Growth at Buried Interfaces with Vascularized Polymers

   https://doi.org/10.1021/acsabm.2c00837  

   Dixon, Brandon; Sui, Chenxi; Briley, Anna; Hsu, Po-Chun; Howell, Caitlin (February 2023, ACS Applied Bio Materials)

   Evaluating surface bacterial growth at buried interfaces can be problematic due to the difficulties associated with obtaining samples. In this work, we present a new method to detect signals from microorganisms at buried interfaces that is nondestructive and can be conducted continuously. Inspired by vascular systems in nature that permit chemical communication between the surface and underlying tissues of an organism, we created a system in which an inert carrier fluid could be introduced into an empty vascular network embedded in a polymer matrix. When a microorganism layer was grown on top, small molecules produced by the growth process would diffuse down into the carrier fluid, which could then be collected and analyzed. We used this system to nondestructively detect signals from a surface layer of Escherichia coli using conductivity, ultraviolet–visible (UV–vis) absorbance spectroscopy, and high-performance liquid chromatography (HPLC) for organic acids, methods that ranged in sensitivity, time-to-result, and cost. Carrier fluid from sample vascularized polymers with surface bacterial growth recorded significantly higher values in both conductivity and absorbance at 350 nm compared to controls with no bacteria after 24 h. HPLC analysis showed three clear peaks that varied between the samples with bacteria and the controls without. Tests tracking the change in signals over 48 h showed clear trends that matched the bacterial growth curves, demonstrating the system’s ability to monitor changes over time. A 2D finite element model of the system closely matched the experimental results, confirming the predictability of the system. Finally, tests using clinically relevant Staphylococcus aureus and Pseudomonas aeruginosa yielded differences in conductivity, absorbance, and HPLC peak areas unique to each species. This work lays the foundation for the use of vascularized polymers as an adaptive system for the continuous, nondestructive detection of surface microorganisms at buried interfaces in both industry and medicine. 

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2. Practical and Instructive Approach to Purify Acetonitrile for a Wide Electrochemical Window

   https://doi.org/10.29356/jmcs.v67i4.2013  

   Ávila-Gutierrez, Mario; Gutierrez-Portocarrero, Salvador; Corono-Elizarrarás, Luis; Alpuche Aviles, Mario A. (September 2023, Journal of the Mexican Chemical Society)

   Because of its large electrochemical window, acetonitrile (MeCN) is one of the most widely used solvents in electrochemistry. It is a suitable solvent for nonaqueous electrolytes that allows studies of cathodic and anodic processes, but electrolyte purification remains challenging. As received, the high-performance liquid chromatography (HPLC) grade is unsuitable for most electroanalytical applications. We present an approach to optimize the purification of HPLC-grade acetonitrile to yield a tetrabutylammonium perchlorate (TBAP)/MeCN electrolyte for experiments in nonaqueous media. We used cyclic voltammetry (CV) to show the background due to impurities and to guide the experimental design to a background current acceptable for CVs of a 1 mM typical concentration of a redox-active molecule. We use 3A molecular sieves, followed by distillation over CaH2 with a final treatment with Al2O3. The optimized procedure yields CH3CN with small background currents, increasing the signal-to-noise ratio and minimizing chemical complications over a wide potential window. Our approach includes discriminating between impurities in the solvent and electrolyte salts; for TBAP, we recrystallize from ethyl acetate and 95 % ethanol. The process and theoretical guidelines apply to other nonaqueous electrolytes dealing with electroactive impurities, including organic molecules, oxygen, and water. 

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3. Rapid organocatalytic chirality analysis of amines, amino acids, alcohols, amino alcohols and diols with achiral iso(thio)cyanate probes

   https://doi.org/10.1039/D1SC02061G  

   Nelson, Eryn; Formen, Jeffrey S.; Wolf, C. (June 2021, Chemical Science)

   The widespread occurrence and significance of chiral compounds does not only require new methods for their enantioselective synthesis but also efficient tools that allow rapid determination of the absolute configuration, enantiomeric composition and overall concentration of nonracemic mixtures. Although chiral analysis is a frequently encountered challenge in the chemical, environmental, materials and health sciences it is typically addressed with slow and laborious chromatographic or NMR spectroscopic techniques. We now show with almost 40 analytes representing 5 different compound classes, including mono-alcohols which are particularly challenging sensing targets, that this task can be solved very quickly by chiroptical sensing with a single, readily available arylisocyanate probe. The probe reacts smoothly and irreversibly with amino and alcohol groups when an organocatalyst is used at room temperature toward urea or carbamate products exhibiting characteristic UV and CD signals above 300 nm. The UV signal induction is not enantioselective and correlated to the total concentration of both enantiomers, the concomitant generation of a CD band allows determination of the enantiomeric composition from the same sample, and the sense of the induced Cotton effect reveals the absolute configuration by comparison with a reference. This approach eliminates complications that can arise when enantiomerically impure NMR derivatizing agents are used and it outperforms time-consuming HPLC protocols. The generation of distinct UV and CD signals at high wavelengths overcomes issues with insufficient resolution of overlapping signals often encountered with chiral NMR solvating agents that rely on weak binding forces. The broad solvent compatibility is another noteworthy and important characteristic of this assay. It addresses frequently encountered problems with insufficient solubility of polar analytes, for example pharmaceuticals, in standard mobile phase mixtures required for chiral HPLC analysis. We anticipate that the broad application spectrum, ruggedness and practicality of organocatalytic chiroptical sensing with aryliso(thio)cyanate probes together with the availability of automated CD multi-well plate readers carry exceptional promise to accelerate chiral compound development projects at reduced cost and with less waste production. 

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4. A comprehensive spectral assay library to quantify the Escherichia coli proteome by DIA/SWATH-MS

   https://doi.org/10.1038/s41597-020-00724-7  

   Midha, Mukul K.; Kusebauch, Ulrike; Shteynberg, David; Kapil, Charu; Bader, Samuel L.; Reddy, Panga Jaipal; Campbell, David S.; Baliga, Nitin S.; Moritz, Robert L. (December 2020, Scientific Data)

   Abstract Data-Independent Acquisition (DIA) is a method to improve consistent identification and precise quantitation of peptides and proteins by mass spectrometry (MS). The targeted data analysis strategy in DIA relies on spectral assay libraries that are generally derived from a priori measurements of peptides for each species. Although Escherichia coli ( E. coli ) is among the best studied model organisms, so far there is no spectral assay library for the bacterium publicly available. Here, we generated a spectral assay library for 4,014 of the 4,389 annotated E. coli proteins using one- and two-dimensional fractionated samples, and ion mobility separation enabling deep proteome coverage. We demonstrate the utility of this high-quality library with robustness in quantitation of the E. coli proteome and with rapid-chromatography to enhance throughput by targeted DIA-MS. The spectral assay library supports the detection and quantification of 91.5% of all E. coli proteins at high-confidence with 56,182 proteotypic peptides, making it a valuable resource for the scientific community. Data and spectral libraries are available via ProteomeXchange (PXD020761, PXD020785) and SWATHAtlas (SAL00222-28). 

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5. Recent Advances in Nanomaterial-Based Aptasensors in Medical Diagnosis and Therapy

   https://doi.org/10.3390/nano11040932  

   Ayodele, Olubunmi O.; Adesina, Adeyinka O.; Pourianejad, Sajedeh; Averitt, Jared; Ignatova, Tetyana (April 2021, Nanomaterials)

   null (Ed.)

   Rapid and accurate diagnosis of various biomarkers associated with medical conditions including early detection of viruses and bacteria with highly sensitive biosensors is currently a research priority. Aptamer is a chemically derived recognition molecule capable of detecting and binding small molecules with high specificity and its fast preparation time, cost effectiveness, ease of modification, stability at high temperature and pH are some of the advantages it has over traditional detection methods such as High Performance Liquid Chromatography (HPLC), Enzyme-linked Immunosorbent Assay (ELISA), Polymerase Chain Reaction (PCR). Higher sensitivity and selectivity can further be achieved via coupling of aptamers with nanomaterials and these conjugates called “aptasensors” are receiving greater attention in early diagnosis and therapy. This review will highlight the selection protocol of aptamers based on Traditional Systematic Evolution of Ligands by EXponential enrichment (SELEX) and the various types of modified SELEX. We further identify both the advantages and drawbacks associated with the modified version of SELEX. Furthermore, we describe the current advances in aptasensor development and the quality of signal types, which are dependent on surface area and other specific properties of the selected nanomaterials, are also reviewed. 

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