Selective Sensing of Epinephrine by Phenylboronic Acid Tethered Carbon Dot.

The present work depicts development of phenylboronic acid (PBA) derived and appended carbon dots (CD1-PBAs) to detect epinephrine with high sensitivity and selectivity against structurally analogous biomolecules like norepinephrine, L-Dopa and glucose. Carbon dots were synthesized by hydrothermal method. Microscopic and spectroscopic studies ensured the suitability of CD1-PBAs for diol sensing. Catecholic-OH groups of epinephrine primarily form covalent adduct with CD1-PBAs via boronate-diol linkage that caused change in absorption intensity of CD1-PBAs. The limit of detection (LOD) for epinephrine was found to be 2.0 nM. For other analogous biomolecules, formation of boronate-diol linkage might have got retarded by the dominant participation of secondary interactions like hydrogen bonding owing to the presence of varying functional moieties. Subsequently, responsiveness in the change in absorbance intensity of CD1-PBAs was weaker compared to that for epinephrine. Hence, a selective and efficient carbon dot (CD1-PBAs) based epinephrine sensor was developed simply by utilizing boronate-diol linkage.

Peptide Amphiphilic Supramolecular Nanogels: Competent Host for Notably Efficient Lipase-Catalyzed Hydrolysis of Water-Insoluble Substrates.

The present work depicts the development of stable nanogels in an aqueous medium that were exploited for efficient surface-active lipase-catalyzed hydrolysis of water-insoluble substrates. Surfactant-coated gel nanoparticles (neutral NG1, anionic NG2, and cationic NG3) were prepared from peptide amphiphilic hydrogelator (G1, G2, and G3, respectively) at different hydrophilic and lipophilic balance (HLB). Chromobacterium viscosum (CV) lipase activity towards hydrolysis of water-insoluble substrates (p-nitrophyenyl-n-alkanoates (C4-C10)) in the presence of nanogels got remarkably improved by ~1.7-8.0 fold in comparison to that in aqueous buffer and other self-aggregates. An increase in hydrophobicity of the substrate led to a notable improvement in lipase activity in the hydrophilic domain (HLB>8.0) of nanogels. The micro-heterogeneous interface of small-sized (10-65 nm) nanogel was found to be an appropriate scaffold for immobilizing surface-active lipase to exhibit superior catalytic efficiency. Concurrently, the flexible conformation of lipase immobilized in nanogels was reflected in its secondary structure having the highest α-helix content from the circular dichroism spectra.

Co2+ Doped Biotinylated Carbon Dot: A Theranostic Agent for Target Specific Killing of Cancer Cells via Hypoxia Induced Apoptosis.

Conventional cancer treatments have systematic side effects that stand against its desirable therapeutic efficacy. Alternative strategies using biochemical features of cancer cells to promote apoptosis are finding notable significance. One such important biochemical feature of malignant cells is hypoxia, alteration of which can lead to cell death. Hypoxia inducible factor 1α (HIF-1α) has the key role in hypoxia generation. Herein, we synthesized biotinylated Co2+ -integrated carbon dot (CoCDb ) that specifically diagnose and selectively killed cancer cells with 3-3.1-fold higher efficiency over non-cancer cells by hypoxia induced apoptosis in absence of traditional therapeutic intervention. Immunoblotting assay in CoCDb treated MDA-MB-231 cells confirmed the increased expression of HIF-1α that was responsible for efficient killing of cancer cells. In 2D cells and 3D tumor spheroid, CoCDb treated cancer cells showed significant apoptosis that make CoCDb a potential theranostic agent.

Access to US primary care physicians for new patients concerned about smoking or weight.

Tobacco smoking and obesity are leading causes of preventable morbidity and mortality in the US, and primary care physicians are the main source of preventive care. However, it is not known whether access for new patients is affected by an expression of interest in preventive care. In a 2015 audit, we called US primary care physicians' offices to request appointment information regarding new patient physicals for simulated patients. Simulated patients were differentiated by smoking concerns (N = 907), weight concerns (N = 867), or no health concerns ("healthy" patients; N = 3561). Additionally, patient profiles varied by race/ethnicity, sex, and insurance type. We also examined whether access differed in states that expanded Medicaid under the Affordable Care Act. We found that physicians' offices were no more likely to offer appointments to patients with smoking concerns than to healthy patients (54% vs. 55%; p-value = 0.56), and patients with smoking concerns were offered fewer appointments than patients with weight concerns (54% vs. 62%, p-value < 0.01). In analyses adjusted for covariates, smoking concerns did not improve appointment offers for any patient group, and reduced Medicare patients' offers in Medicaid expansion states by 9 percentage points relative to healthy patients (95% CI: -16, -2). Health concerns did not statistically significantly affect waits-to-appointment. Our results suggest that patients with smoking concerns are no more likely to be offered new patient appointments than those with no health concerns. The greater likelihood of appointment offers for some patients with weight concerns is encouraging for obesity prevention and management.

State Medicaid fees and access to primary care physicians.

Medicaid and uninsured patients are disadvantaged in access to care and are disproportionately Black and Hispanic. Using a national audit of primary care physicians, we examine the relationship between state Medicaid fees for primary care services and access for Medicaid, Medicare, uninsured, and privately insured patients who differ by race/ethnicity and sex. We found that states with higher Medicaid fees had higher probabilities of appointment offers and shorter wait times for Medicaid patients, and lower probabilities of appointment offers and longer wait times for uninsured patients. Appointment offers and wait times for Medicare and privately insured patients were unaffected by Medicaid fees. At mean state Medicaid fees, our analysis predicts a 27-percentage-point disadvantage for Medicaid versus Medicare in appointment offers. This decreases to 6 percentage points when Medicaid and Medicare fees are equal, suggesting that permanent fee parity with Medicare could eliminate most of the disparity in appointment offers for Medicaid patients. The predicted decrease in the disparity is smaller for Black and Hispanic patients than for White patients. Our research highlights the importance of considering the effects of policy on nontarget patient groups, and the consequences of seemingly race-neutral policies on racial/ethnic and sex-based disparities.

Offers of appointments with nurse practitioners if a requested physician is unavailable.

BACKGROUND AND PURPOSE: Access to primary care remains a problem for a substantial portion of the U.S. population, and is predicted to worsen due to an aging population and the increasing burden of chronic diseases. Better integration of nurse practitioners (NPs) into the primary care workforce is a possible solution. We examine offers of appointments with NPs if a requested primary care physician is unavailable. METHODS: Data are from a 2013 audit (simulated patient) study requesting appointment information from a national random sample of primary care physicians. Outcome variables include appointment offers, wait-to-appointment times, and appointment offers with alternate providers, including NPs. CONCLUSIONS: Of 922 calls to primary care physicians serving the general adult population, 378 (41%) offered appointments with the requested physician. Alternate providers were offered by 63 (7%), including nine offers with NPs (<1%). Mean wait-to-appointment for NPs (3.6 days) was statistically significantly shorter (p-values < .01) than for requested physicians (22.5 days) or non-NP alternate providers (23.9 days). IMPLICATIONS FOR PRACTICE: NPs are an important part of the primary care workforce, and new patients seeking primary care physicians may substantially reduce their wait times if an NP is offered.

Selective virus detection in complex sample matrices with photonic crystal optical cavities.

Rapid, sensitive, and selective detection of viruses is critical for applications in medical diagnostics, biosecurity, and environmental safety. In this article, we report the application of a point-defect-coupled W1 photonic crystal (PhC) waveguide biosensor to label-free optical detection of viruses. Fabricated on a silicon-on-insulator (SOI) substrate using electron-beam (e-beam) lithography and reactive-ion-etching, the PhC sensing platform allows optical detection based on resonant mode shifts in response to ambient refractive index changes produced by infiltration of target biomaterial within the holes of the PhC structure. Finite difference time domain (FDTD) calculations were performed to assist with design of the sensor, and to serve as a theoretical benchmark against which experimental results could be compared. Using Human Papillomavirus virus-like particles (VLPs) spiked in 10% fetal bovine serum as a model system, we observed a limit of detection of 1.5 nM in simple (buffer only) or complex (10% serum) sample matrices. The use of anti-VLP antibodies specific for intact VLPs with the PhC sensors provided highly selective VLP detection.

1-D and 2-D photonic crystals as optical methods for amplifying biomolecular recognition.

Label-free sensing strategies are an intensely studied and increasingly used alternative to signal amplification via fluorescent labels and enzymatic methods. This article discusses one class of optical sensors, termed "photonic crystals", that effectively amplify binding events (such as analyte capture) via strong light-matter interactions.

Silicon photonic crystal nanocavity-coupled waveguides for error-corrected optical biosensing.

A photonic crystal (PhC) waveguide based optical biosensor capable of label-free and error-corrected sensing was investigated in this study. The detection principle of the biosensor involved shifts in the resonant mode wavelength of nanocavities coupled to the silicon PhC waveguide due to changes in ambient refractive index. The optical characteristics of the nanocavity structure were predicted by FDTD theoretical methods. The device was fabricated using standard nanolithography and reactive-ion-etching techniques. Experimental results showed that the structure had a refractive index sensitivity of 10(-2) RIU. The biosensing capability of the nanocavity sensor was tested by detecting human IgG molecules. The device sensitivity was found to be 2.3±0.24×10(5) nm/M with an achievable lowest detection limit of 1.5 fg for human IgG molecules. Additionally, experimental results demonstrated that the PhC devices were specific in IgG detection and provided concentration-dependent responses consistent with Langmuir behavior. The PhC devices manifest outstanding potential as microscale label-free error-correcting sensors, and may have future utility as ultrasensitive multiplex devices.

Electrically active magnetic nanoparticles as novel concentrator and electrochemical redox transducer in Bacillus anthracis DNA detection.

Magnetic polymer nanostructures are a new class of multifunctional nanomaterials that are recently being explored in biosensor devices. In this paper, for the first time we report the novel application of electrically active magnetic (EAM) nanoparticles as concentrator of DNA targets as well as electrochemical transducers for detection of the Bacillus anthracis protective antigen A (pag A) gene. The EAM nanoparticles are synthesized by chemical polymerization and have dimensions of 80-100 nm. The biosensor detection encompasses two sets of DNA probes that are specific to the target gene: the detector probe labeled with the EAM nanoparticles and the biotinylated capture probe. The DNA targets are double hybridized to the detector and the capture probes and concentrated from nonspecific DNA fragments by applying a magnetic field. Subsequently, the DNA sandwiched targets (EAM-detector probe-DNA target-capture probe-biotin) are captured on streptavidin modified screen printed carbon electrodes through the biotinylated capture probes. Detection is achieved electrochemically by measuring the oxidation-reduction signal of the EAM nanoparticles. Preliminary results indicate that the biosensor is able to detect the redox signal of the EAM nanoparticles at DNA concentrations as low as 0.01 ng/µl.

Electrically active polyaniline coated magnetic (EAPM) nanoparticle as novel transducer in biosensor for detection of Bacillus anthracis spores in food samples.

Electrically active polyaniline coated magnetic (EAPM) nanoparticle-based biosensor has been developed for the detection of Bacillus anthracis endospores in contaminated food samples. The 100 nm-diameter EAPM nanoparticles are synthesized from aniline monomer (made electrically active by acid doping) coating the surface of gamma iron oxide cores. The magnetic, electrical, and structural characteristics of the synthesized EAPM nanoparticles have been studied using superconducting quantum interference device (SQUID), four-point probe, and transmission electron microscopy (TEM). Room temperature hysteresis of the synthesized nanoparticles shows a saturation magnetization value of 44.1 emu/g. The EAPM nanoparticles are biologically modified to act as an immunomagnetic concentrator of B. anthracis spores from lettuce, ground beef and whole milk samples and are directly applied to a direct-charge transfer biosensor. The detection mechanism of the biosensor depends on the capillary flow of the captured spores on the biosensor surface along with direct-charge transfer across the EAPM nanoparticles. Experimental results indicate that the biosensor is able to detect B. anthracis spores at concentrations as low as 4.2 x 10(2)spores/ml from the samples. The EAPM-based biosensor detection system is fast and reliable with a total detection time of 16 min.

Nanowire labeled direct-charge transfer biosensor for detecting Bacillus species.

A direct-charge transfer (DCT) biosensor was developed for the detection of the foodborne pathogen, Bacillus cereus. The biosensor was fabricated using antibodies as the sensing element and polyaniline nanowire as the molecular electrical transducer. The sensor design consisted of four membrane pads, namely, sample application, conjugate, capture and absorption pads. Two sets of polyclonal antibodies, secondary antibodies conjugated with polyaniline nanowires and capture antibodies were applied to the conjugate and the capture pads of the biosensor, respectively. The detection technique was based on capillary flow action which allowed the liquid sample to move from one membrane to another. The working principle involved antigen-antibody interaction and direct electron charge flow to generate a resistance signal that was being recorded. Detection from sample application to final results was completed in 6 min in a reagentless process. Experiments were conducted to find the best performance of the biosensors by varying polyaniline types and concentrations. Polyaniline protonated with hydrochloric acid, emeraldine salt and polyaniline protonated with perchloric acid were the three kinds of polyaniline used in this study. The biosensor sensitivity in pure cultures of B. cereus was found to be 10(1) to 10(2)CFU/ml. Results indicated that using emeraldine salt at a concentration of 0.25 g/ml gave the best biosensor performance in terms of sensitivity. The biosensor was also found to be specific in detecting the presence of B. cereus in a mixed culture of different Bacillus species and other foodborne pathogens. The speed, sensitivity and ease-of-use of this biosensor make it a promising device for rapid field-based diagnosis towards the protection of our food supply chain. The phenotypic and genotypic similarities between B. cereus and Bacillus anthracis will also allow this biosensor to serve as an excellent model for the detection of B. anthracis.

A multi-channel femtoampere-sensitivity conductometric array for biosensing applications.

Rapid detection of pathogens using field deployable biosensors requires integrated sensing and data processing. Detection of low concentration of biological agents is possible using accurate and real-time signal characterization devices. This paper presents a multi-channel conductometric array that can detect and measure current up to femtoampere range. The architecture uses a novel semi-synchronous SigmaDelta modulation that allows measurement of ultra-small currents by using a hysteretic comparison technique. The architecture achieves higher energy efficiency over a conventional SigmaDelta by reducing the total switching cycles of the comparator. A 3 mm x 3 mm chip implementing a 42 channel potentiostat array has been prototyped in a 0.5 microm CMOS technology. Measured results show 10 bits of resolution, with a sensitivity of upto 50 fA of current. The power consumption of the potentiostat is 11 microW per channel at a sampling rate of 250 kHz. The multi-channel potentiostat has been integrated with a conductometric biosensor for field deployable applications. Results with a Bacillus Cereus based biosensor demonstrate the effectiveness of the potentiostat in characterizing different concentration levels of pathogens in realtime.