Evaluation of Direct Detection Protocols for Poliovirus from Stool Samples of Acute Flaccid Paralysis Patients

Polio surveillance in the Global Polio Eradication Initiative has been conducted with virus isolation from stool samples of acute flaccid paralysis (AFP) cases. Under the current biorisk management/regulations, challenges arise in the timelines of the report, sensitivity of the test and containment of poliovirus (PV) isolates. In the present study, we evaluated protocols of previously reported direct detection (DD) methods targeting the VP1 or VP4-VP2 regions of the PV genome in terms of sensitivity and sequencability. An optimized protocol targeting the entire-capsid region for the VP1 sequencing showed a high sensitivity (limit of detection = 82 copies of PV genome) with a simpler and faster reaction than reported ones (i.e., with the addition of all the primers at the start of the reaction, the RT-PCR reaction finishes within 2.5 h). The DD methods targeting the VP1 region detected PV in 60 to 80% of PV-positive stool samples from AFP cases; however, minor populations of PV strains in the samples with virus mixtures were missed by the methods. Sequencability of the DD methods was primarily determined by the efficiency of the PCRs for both Sanger and nanopore sequencing. The DD method targeting the VP4-VP2 region showed higher sensitivity than that targeting the VP1 region (limit of detection = 25 copies of PV genome) and successfully detected PV from all the stool samples examined. These results suggest that DD methods are effective for the detection of PV and that further improvement of the sensitivity is essential to serve as an alternative to the current polio surveillance algorithm.

Direct Detection of Lyme Borrelia: Recent Advancement and Use of Aptamer Technology

Borrelia burgdorferi sensu lato (B. burgdorferi s.l.), which is predominantly spread by ticks, is the cause of Lyme disease (LD), also known as Lyme borreliosis, one of the zoonotic diseases affecting people. In recent years, LD has become more prevalent worldwide, even in countries with no prior records. Currently, Lyme Borrelia detection is achieved through nucleic acid amplification, antigen detection, microscopy, and in vitro culture. Nevertheless, these methods lack sensitivity in the early phase of the disease and, thus, are unable to confirm active infection. This review briefly discusses the existing direct detection methods of LD. Furthermore, this review also introduces the use of aptamer technology integrated with biosensor platforms to detect the Borrelia antigen. This aptamer technology could be explored using other biosensor platforms targeting whole Borrelia cells or specific molecules to enhance Borrelia detection in the future.

Lateral Flow Strip Biosensors for Foodborne Pathogenic Bacteria via Direct and Indirect Sensing Strategies: A Review

Rapid and sensitive detection of foodborne pathogenic bacteria is particularly important for the prevention and control of foodborne diseases. The lateral flow strip biosensor (LFSB) is one of the most promising point-of-care detection tools and has been widely used in food safety monitoring. This review introduces recent advances in the detection of foodborne pathogenic bacteria using LFSBs. According to different bacterial biomarkers, we summarize the direct and indirect sensing strategies of bacterial LFSBs. The direct sensing strategies for whole bacterial cells are divided into antibodies, antibody alternatives, and label-free according to the recognition elements. The indirect sensing strategies refer to the detection of bacterial nucleic acids and metabolites. Next, we compare and discuss the applications of direct and indirect sensing strategies. Finally, the existing challenges, future perspectives, and development directions are discussed, which will facilitate the theoretical innovation and practical application for bacterial LFSBs.

Printable Perovskite Diodes for Broad-Spectrum Multienergy X-Ray Detection

Multienergy X-ray detection is critical to effectively differentiate materials in a variety of diagnostic radiology and nondestructive testing applications. Silicon and selenium X-ray detectors are the most common for multienergy detection; however, these present poor energy discrimination across the broad X-ray spectrum and exhibit limited spatial resolution due to the high thicknesses required for radiation attenuation. Here, an X-ray detector based on solution-processed thin-film metal halide perovskite that overcomes these challenges is introduced. By harnessing an optimized n-i-p diode configuration, operation is achieved across a broad range of soft and hard X-ray energies stemming from 0.1 to 10's of keV. Through detailed experimental and simulation work, it is shown that optimized Cs_0.1 FA_0.9 PbI₃ perovskites effectively attenuate soft and hard X-rays, while also possessing excellent electrical properties to result in X-ray detectors with high sensitivity factors that exceed 5 × 10³ µ C   G y Vac - 1   cm - 2 $\mu {\rm{C}}\;{{\bf Gy}}_{{\rm{Vac}}}^{ - 1}\;{\rm{c}}{{\rm{m}}^{ - 2}}$ and 6 × 10⁴ µC Gy^-1 cm^-2 within soft and hard X-ray regimes, respectively. Harnessing the solution-processable nature of the perovskites, roll-to-roll printable X-ray detectors on flexible substrates are also demonstrated.

Challenges in Direct Detection of Flaviviruses: A Review

Arthropods transmit arboviruses via mosquito and tick bites to humans and other animals. The genus flavivirus, which causes diseases, sequelae, and thousands of deaths, mainly in developing and underdeveloped countries, is among the arboviruses of interest to public health. Given the importance of early and accurate diagnosis, this review analyzes the methods of direct detection of flaviviruses, such as reverse transcription loop-mediated isothermal amplification, microfluidics, localized surface plasmon resonance, and surface-enhanced Raman scattering, and presents the advantages, disadvantages, and detection limits identified in studies reported in the literature for each methodology. Among the different methods available, it is essential to balance four fundamental indicators to determine the ideal test: good sensitivity, high specificity, low false positive rate, and rapid results. Among the methods analyzed, reverse transcription loop-mediated isothermal amplification stands out, owing to result availability within a few minutes, with good sensitivity and specificity; in addition, it is the best-characterized methodology.

Direct detection of elephant endotheliotropic herpesvirus 1 (EEHV1) DNA in heparinized plasma by loop-mediated isothermal amplification

Elephant endotheliotropic herpesvirus (EEHV) causes a fatal hemorrhagic disease and is a significant cause of mortality in juvenile Asian elephants. A loop-mediated isothermal amplification (LAMP) method was developed to rapidly diagnose EEHV viremia. However, extracting DNA from whole blood samples to perform LAMP hampers diagnosis in a field setting. Here, we established the Direct-LAMP method, using heparinized plasma without extracting the DNA to speed up and simplify the test. EEHV-positive specimens were tested using the Direct-LAMP. The detection limit was calculated to be 10^1.3 copies/μL using the mimetic samples, which was almost identical to the value determined in LAMP in which DNA was extracted. Hence, the Direct-LAMP provided a more rapid diagnosis to save, which could prevent elephant deaths.

Quantifying Microalgae Growth by the Optical Detection of Glucose in the NIR Waveband

Microalgae have become a popular area of research over the past few decades due to their enormous benefits to various sectors, such as pharmaceuticals, biofuels, and food and feed. Nevertheless, the benefits of microalgae cannot be fully exploited without the optimization of their upstream production. The growth of microalgae is commonly measured based on the optical density of the sample. However, the presence of debris in the culture and the optical absorption of the intercellular components affect the accuracy of this measurement. As a solution, this paper introduces the direct optical detection of glucose molecules at 940-960 nm to accurately measure the growth of microalgae. In addition, this paper also discusses the effects of the presence of glucose on the absorption of free water molecules in the culture. The potential of the optical detection of glucose as a complement to the commonly used optical density measurement at 680 nm is discussed in this paper. Lastly, a few recommendations for future works are presented to further verify the credibility of glucose detection for the accurate determination of microalgae's growth.

Seroprevalence, Direct Detection and Risk Factors for Toxoplasma gondii Infection in Pigs in Serbia, and Influence of Biosecurity Measures

Consumption of Toxoplasma gondii contaminated pork is a major risk factor for human infection. We thus conducted a cross-sectional survey on the seroprevalence of T. gondii infection in a representative sample of slaughter pigs from throughout Serbia and examined the influence of farm biosecurity-related risk factors on infection. In addition, direct detection of the parasite (by mouse bioassay) or its DNA was performed in the hearts of a subset of seropositive sows. The overall seroprevalence in the sample of 825 pigs as determined by the modified agglutination test (MAT) was 16.5%. Older age and inadequate rodent control were independent infection risk factors for pigs. In a subset of 581 pigs with complete biosecurity-related data, in addition to older age, smallholders’ finishing type farms (as opposed to farrow-to-finish), multispecies farming, and origin from Western and Central and South-Eastern Serbia (vs. the Northern region), all increased the risk of infection, while the absence of disinfection boot-dips in front of each barn and Belgrade district origin (vs. the Northern region) were associated with a 62% and 75% lower risk of infection, respectively. Evidence of viable parasites was obtained in 13 (41.9%) of the 31 bioassayed sow hearts, of which by isolation of brain cysts in seven, by detection of T. gondii DNA in an additional four, and by serology in another two. Recovery of brain cysts mostly (5/7) from sows with a MAT titre of ≥1:100 indicates the risk for consumers. These results highlight the public health risk from pork consumption and point to mandatory use of professional rodent control services, abstaining from multispecies farming, keeping disinfection boot-dips clean and freshly refilled, as well as strict implementation of zoo-hygienic measures on smallholders’ farms as specific farm biosecurity measures needed for its reduction.

Direct detection of dark matter-APPEC committee report

This report provides an extensive review of the experimental programme of direct detection searches of particle dark matter. It focuses mostly on European efforts, both current and planned, but does it within a broader context of a worldwide activity in the field. It aims at identifying the virtues, opportunities and challenges associated with the different experimental approaches and search techniques. It presents scientific and technological synergies, both existing and emerging, with some other areas of particle physics, notably collider and neutrino programmes, and beyond. It addresses the issue of infrastructure in light of the growing needs and challenges of the different experimental searches. Finally, the report makes a number of recommendations from the perspective of a long-term future of the field. They are introduced, along with some justification, in the opening overview and recommendations section and are next summarised at the end of the report. Overall, we recommend that the direct search for dark matter particle interactions with a detector target should be given top priority in astroparticle physics, and in all particle physics, and beyond, as a positive measurement will provide the most unambiguous confirmation of the particle nature of dark matter in the Universe.

Direct multiplex recombinase polymerase amplification for rapid detection of S taphylococcus aureus and P seudomonas aeruginosa in food

Food and beverage poisoning is detrimental to people's health since it can lead to fever, stomachaches, and even death. To rapidly detect the presence of foodborne pathogens, conventional PCR assays are currently widely employed. Meanwhile, isothermal PCR methods, in which the amplification reactions take place at a low and constant temperature, have lately emerged as effective and alternative means for quickly identifying pathogens in low-resource settings. Staphylococcus aureus and Pseudomonas aeruginosa are two of the most concerning foodborne bacterial infections. In this work, an isothermal PCR assay based on the Recombinase Polymerase Amplification (RPA) method was developed to simultaneously detect S. aureus and P. aeruginosa with high sensitivity and specificity. The limit of detection for multiplex RPA was 10 and 30 fg/reaction of S. aureus and P. aeruginosa genomic DNA, respectively. Furthermore, the reaction time was reduced to only 25 minutes, with a low incubation temperature of 39°C. Multiplex RPA reactions, in particular, were successful in directly identifying as low as 1 and 5 CFU/reaction of S. aureus and P. aeruginosa cells, respectively, without the need for DNA genome extraction. Moreover, the multiplex RPA reliably detected the two foodborne bacteria in milk, fruit juice, and bottled water samples. In conclusion, the direct multiplex RPA reported in this work offers a quick, easy, sensitive, and effective alternative approach for detecting the presence of S. aureus and P. aeruginosa without the requirement of a pricey instrument or highly-trained personnel.

Detection of Enterovirus D68 in Wastewater Samples from the UK between July and November 2021

Infection with enterovirus D68 (EV-D68) has been linked with severe neurological disease such as acute flaccid myelitis (AFM) in recent years. However, active surveillance for EV-D68 is lacking, which makes full assessment of this association difficult. Although a high number of EV-D68 infections were expected in 2020 based on the EV-D68's known biannual circulation patterns, no apparent increase in EV-D68 detections or AFM cases was observed during 2020. We describe an upsurge of EV-D68 detections in wastewater samples from the United Kingdom between July and November 2021 mirroring the recently reported rise in EV-D68 detections in clinical samples from various European countries. We provide the first publicly available 2021 EV-D68 sequences showing co-circulation of EV-D68 strains from genetic clade D and sub-clade B3 as in previous years. Our results show the value of environmental surveillance (ES) for the early detection of circulating and clinically relevant human viruses. The use of a next-generation sequencing (NGS) approach helped us to estimate the prevalence of EV-D68 viruses among EV strains from other EV serotypes and to detect EV-D68 minor variants. The utility of ES at reducing gaps in virus surveillance for EV-D68 and the possible impact of nonpharmaceutical interventions introduced to control the COVID-19 pandemic on EV-D68 transmission dynamics are discussed.

Simulating 50 keV X-ray Photon Detection in Silicon with a Down-Conversion Layer

Simulation results are presented that explore an innovative, new design for X-ray detection in the 20-50 keV range that is an alternative to traditional direct and indirect detection methods. Typical indirect detection using a scintillator must trade-off between absorption efficiency and spatial resolution. With a high-Z layer that down-converts incident photons on top of a silicon detector, this design has increased absorption efficiency without sacrificing spatial resolution. Simulation results elucidate the relationship between the thickness of each layer and the number of photoelectrons generated. Further, the physics behind the production of electron-hole pairs in the silicon layer is studied via a second model to shed more light on the detector's functionality. Together, the two models provide a greater understanding of this detector and reveal the potential of this novel form of X-ray detection.

Culture-Independent Detection of Poliovirus in Stool Samples by Direct RNA Extraction

Laboratory surveillance for poliovirus (PV) relies on virus isolation by cell culture to identify PV in stool specimens from acute flaccid paralysis (AFP) cases. Although this method successfully identifies PV, it is time-consuming and necessitates the additional biorisk of growing live virus in an increasingly polio-free world. To reduce the risk of culturing PV, the Global Polio Laboratory Network (GPLN) must switch to culture-independent diagnostic methods with sensitivity at least equivalent to that of cell culture procedures. Five commercial nucleic acid extraction kits and one enrichment method were tested for PV extraction efficiency. RNA yield was measured using real-time reverse transcription (RT)-PCR. Based on greater RNA yield, compared with the other kits, the Quick-RNA viral kit was selected for further testing and was optimized using an RNA extraction procedure for stool suspensions. RNA extraction was retrospectively tested with 182 stool samples that had previously tested positive for PVs, in parallel with the standard GPLN virus isolation algorithm. After virus isolation or RNA extraction, real-time RT-PCR assays were performed. RNA extraction was significantly more sensitive than virus isolation (McNemar’s test, P < 0.001). Thereafter, the RNA extraction method was tested in parallel for 202 prospective samples; RNA extraction and virus isolation were not significantly different from each other (McNemar’s test, P = 0.13). Direct RNA extraction was noninferior to current cell culture methods for detecting PV in stool samples. Our results show that direct RNA extraction can make downstream manipulation safer and can reduce the risk of accidental posteradication viral release. The method is amenable to implementation in a wide variety of polio laboratories.

IMPORTANCE Successfully identifying poliovirus from acute flaccid paralysis (AFP) cases is a vital role of the Global Polio Laboratory Network to achieve the goals of the Global Polio Eradication Initiative. Currently, laboratory surveillance relies on virus isolation by cell culture to test for PV present in stool samples. Although this method can identify polioviruses, laboratories must switch to culture-independent methods to reduce the risk associated with growing live viruses in a soon-to-be polio-free world. By implementing this streamlined method, in combination with real-time RT-PCR, laboratories can quickly screen for and type polioviruses of programmatic importance to support the final stages of global polio eradication.

Circularly Polarized Photodetectors Based on Chiral Materials: A Review

Circularly polarized light (CPL) plays an important role in many photonic techniques, including tomographic scanning based on circular polarization ellipsometry, optical communication and information of spin, and quantum-based optical calculation and information processing. To fully exploit the functions of CPL in these fields, integrated photoelectric sensors capable of detecting CPL are essential. Photodetectors based on chiral materials can directly detect CPL due to their intrinsic optical activity, without the need to be coupled with polarizers and quarter-wave plates as in conventional photodetectors. This review summarizes the recent research progress in CPL photodetectors based on chiral materials. We first briefly introduce the CPL photodetectors based on different types of chiral materials and their working principles. Finally, current challenges and future opportunities in the development of CPL photodetectors are prospected.

Direct Detection of Streptococcus suis from Cerebrospinal Fluid, Positive Hemoculture, and Simultaneous Differentiation of Serotypes 1, 1/2, 2, and 14 within Single Reaction

Streptococcus suis is an emerging zoonotic bacterium causing septicemia and meningitis in humans. Due to rapid disease progression, high mortality rate, and many underdiagnosed cases by time-consuming routine identification methods, alternative diagnostic testing is essential. Among 29 broadly accepted S. suis serotypes, serotypes 2 and 14 are high prevalent; however, many PCR assays showed an inability to differentiate serotype 2 from 1/2, and 1 from 14. In this study, we developed and validated a new multiplex PCR assay that facilitates the identification of only the 29 true serotypes of S. suis and simultaneously differentiates serotypes 1, 1/2, 2, and 14 within a single reaction. Importantly, the multiplex PCR could detect S. suis directly from positive hemocultures and CSF. The results revealed high sensitivity, specificity, and 100% accuracy with almost perfect agreement (κ = 1.0) compared to culture and serotyping methods. Direct detection enables a decrease in overall diagnosis time, rapid and efficient treatment, reduced fatality rates, and proficient disease control. This multiplex PCR offers a rapid, easy, and cost-effective method that can be applied in a routine laboratory. Furthermore, it is promising for developing point-of-care testing (POCT) for S. suis detection in the future.

Direct Testing for KPC-Mediated Carbapenem Resistance from Blood Samples Using a T2 Magnetic Resonance Based Assay

Molecular-based carbapenem resistance testing in Gram-negative bacterial bloodstream infections (BSIs) is currently limited because of the reliance on positive blood culture (BC) samples. The T2Resistance™ panel may now allow the detection of carbapenemase- and other β-lactamase encoding genes directly from blood samples. We detected carbapenem resistance genes in 11 (84.6%) of 13 samples from patients with BC-documented BSIs (10 caused by KPC-producing Klebsiellapneumoniae and 1 caused by VIM/CMY-producing Citrobacter freundii). Two samples that tested negative for carbapenem resistance genes were from patients with BC-documented BSIs caused by KPC-producing K. pneumoniae who were receiving effective antibiotic therapy. In conclusion, our findings suggest that the T2Resistance™ panel can be a reliable tool for diagnosing carbapenem-resistant Gram-negative bacterial BSIs.

Rapid Increase of SARS-CoV-2 Variant B.1.1.7 Detected in Sewage Samples from England between October 2020 and January 2021

SARS-CoV-2 variants with multiple amino acid mutations in the spike protein are emerging in different parts of the world, raising concerns regarding their possible impact on human immune response and vaccine efficacy against the virus. Recently, a variant named lineage B.1.1.7 was detected and shown to be rapidly spreading across the UK since November 2020. As surveillance for these SARS-CoV-2 variants of concern (VOCs) becomes critical, we have investigated the use of environmental surveillance (ES) for the rapid detection and quantification of B.1.1.7 viruses in sewage as a way of monitoring its expansion that is independent on the investigation of identified clinical cases. Next-generation sequencing analysis of amplicons synthesized from sewage concentrates revealed the presence of B.1.1.7 mutations in viral sequences, first identified in a sample collected in London on 10 November 2020 and shown to rapidly increase in frequency to >95% in January 2021, in agreement with clinical data over the same period. We show that ES can provide an early warning of VOCs becoming prevalent in the population and that, as well as B.1.1.7, our method can detect VOCs B.1.351 and P.1, first identified in South Africa and Brazil, respectively, and other viruses carrying critical spike mutation E484K, known to have an effect on virus antigenicity. Although we did not detect such mutation in viral RNAs from sewage, we did detect mutations at amino acids 478, 490, and 494, located close to amino acid 484 in the spike protein structure and known to also have an effect on antigenicity. IMPORTANCE The recent appearance and growth of new SARS-CoV-2 variants represent a major challenge for the control of the COVID-19 pandemic. These variants of concern contain mutations affecting antigenicity, which raises concerns on their possible impact on human immune response to the virus and vaccine efficacy against them. Here, we show how environmental surveillance for SARS-CoV-2 can be used to help us understand virus transmission patterns and provide an early warning of variants becoming prevalent in the population. We describe the detection and quantification of variant B.1.1.7, first identified in southeast England in sewage samples from London (UK) before widespread transmission of this variant was obvious from clinical cases. Variant B.1.1.7 was first detected in a sample from early November 2020, with the frequency of B.1.1.7 mutations detected in sewage rapidly increasing to >95% in January 2021, in agreement with increasing SARS-CoV-2 infections associated with B.1.1.7 viruses.

Rapid Increase of SARS-CoV-2 Variant B.1.1.7 Detected in Sewage Samples from England between October 2020 and January 2021

SARS-CoV-2 variants with multiple amino acid mutations in the spike protein are emerging in different parts of the world, raising concerns regarding their possible impact on human immune response and vaccine efficacy against the virus. Recently, a variant named lineage B.1.1.7 was detected and shown to be rapidly spreading across the UK since November 2020. As surveillance for these SARS-CoV-2 variants of concern (VOCs) becomes critical, we have investigated the use of environmental surveillance (ES) for the rapid detection and quantification of B.1.1.7 viruses in sewage as a way of monitoring its expansion that is independent on the investigation of identified clinical cases. Next-generation sequencing analysis of amplicons synthesized from sewage concentrates revealed the presence of B.1.1.7 mutations in viral sequences, first identified in a sample collected in London on 10 November 2020 and shown to rapidly increase in frequency to >95% in January 2021, in agreement with clinical data over the same period. We show that ES can provide an early warning of VOCs becoming prevalent in the population and that, as well as B.1.1.7, our method can detect VOCs B.1.351 and P.1, first identified in South Africa and Brazil, respectively, and other viruses carrying critical spike mutation E484K, known to have an effect on virus antigenicity. Although we did not detect such mutation in viral RNAs from sewage, we did detect mutations at amino acids 478, 490, and 494, located close to amino acid 484 in the spike protein structure and known to also have an effect on antigenicity. IMPORTANCE The recent appearance and growth of new SARS-CoV-2 variants represent a major challenge for the control of the COVID-19 pandemic. These variants of concern contain mutations affecting antigenicity, which raises concerns on their possible impact on human immune response to the virus and vaccine efficacy against them. Here, we show how environmental surveillance for SARS-CoV-2 can be used to help us understand virus transmission patterns and provide an early warning of variants becoming prevalent in the population. We describe the detection and quantification of variant B.1.1.7, first identified in southeast England in sewage samples from London (UK) before widespread transmission of this variant was obvious from clinical cases. Variant B.1.1.7 was first detected in a sample from early November 2020, with the frequency of B.1.1.7 mutations detected in sewage rapidly increasing to >95% in January 2021, in agreement with increasing SARS-CoV-2 infections associated with B.1.1.7 viruses.

Detection and Typing of Human Enteroviruses from Clinical Samples by Entire-Capsid Next Generation Sequencing

There are increasing concerns of infections by enteroviruses (EVs) causing severe disease in humans. EV diagnostic laboratory methods show differences in sensitivity and specificity as well as the level of genetic information provided. We examined a detection method for EVs based on next generation sequencing (NGS) analysis of amplicons covering the entire capsid coding region directly synthesized from clinical samples. One hundred and twelve clinical samples from England; previously shown to be positive for EVs, were analyzed. There was high concordance between the results obtained by the new NGS approach and those from the conventional Sanger method used originally with agreement in the serotypes identified in the 83 samples that were typed by both methods. The sensitivity and specificity of the NGS method compared to those of the conventional Sanger sequencing typing assay were 94.74% (95% confidence interval, 73.97% to 99.87%) and 97.85% (92.45% to 99.74%) for Enterovirus A, 93.75% (82.80% to 98.69%) and 89.06% (78.75% to 95.49%) for Enterovirus B, 100% (59.04% to 100%) and 98.10% (93.29% to 99.77%) for Enterovirus C, and 100% (75.29% to 100%) and 100% (96.34% to 100%) for Enterovirus D. The NGS method identified five EVs in previously untyped samples as well as additional viruses in some samples, indicating co-infection. This method can be easily expanded to generate whole-genome EV sequences as we show here for EV-D68. Information from capsid and whole-genome sequences is critical to help identifying the genetic basis for changes in viral properties and establishing accurate spatial-temporal associations between EV strains of public health relevance.

Accuracy of matrix-assisted laser desorption ionization time-of-flight mass spectrometry for direct bacterial identification from culture-positive urine samples

Background

Urinary tract infection (UTI) is one of the most frequent reasons for antimicrobial therapy. In typical clinical setting, 18–48 h is needed to identify pathogens by urine culture. A rapid method for pathogenic UTI diagnosis by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been developed in recent years.

Methods

This meta-analysis systematically evaluated the accuracy of MALDI-TOF MS for direct identification of bacteria from culture-positive urine samples. We queried the electronic database of Medline and Web of Science to obtain relevant articles.

Results

Nineteen articles involving 4,579 isolates were included after final selection in the meta-analysis. The random-effects pooled identification accuracy of MALDI-TOF MS was 0.82 with 95% confidence interval of 0.79 to 0.86 at the species level. For Gram-negative isolates, the correct identification performance of the species ranged from 0.54 to 0.98, with a cumulative rate of 0.87 (95% CI: 0.83 to 0.91). For Gram-positive isolates, the correct identification rate ranged from 0.32 to 0.80, with a cumulative rate of 0.59 (95% CI: 0.49 to 0.68).

Conclusions

MALDI-TOF MS provides a reliable direct identification of bacteria, particularly in cases of Gram-negative isolates, from clinical urine specimens. Nevertheless, the identification accuracy of this method is moderate for Gram-positive bacteria.

Nucleic Acid-Based Sensing Techniques for Diagnostics and Surveillance of Influenza

Influenza virus poses a threat to global health by causing seasonal outbreaks as well as three pandemics in the 20th century. In humans, disease is primarily caused by influenza A and B viruses, while influenza C virus causes mild disease mostly in children. Influenza D is an emerging virus found in cattle and pigs. To mitigate the morbidity and mortality associated with influenza, rapid and accurate diagnostic tests need to be deployed. However, the high genetic diversity displayed by influenza viruses presents a challenge to the development of a robust diagnostic test. Nucleic acid-based tests are more accurate than rapid antigen tests for influenza and are therefore better candidates to be used in both diagnostic and surveillance applications. Here, we review various nucleic acid-based techniques that have been applied towards the detection of influenza viruses in order to evaluate their utility as both diagnostic and surveillance tools. We discuss both traditional as well as novel methods to detect influenza viruses by covering techniques that require nucleic acid amplification or direct detection of viral RNA as well as comparing advantages and limitations for each method. There has been substantial progress in the development of nucleic acid-based sensing techniques for the detection of influenza virus. However, there is still an urgent need for a rapid and reliable influenza diagnostic test that can be used at point-of-care in order to enhance responsiveness to both seasonal and pandemic influenza outbreaks.

Distribution of enterovirus genotypes detected in clinical samples in Hungary, 2010-2018

This report provides the findings of a retrospective surveillance study on the emergence and circulation of enteroviruses with their associated clinical symptoms over a nine-year period detected at the National Enterovirus Reference Laboratory in Hungary between 2010-2018.Enterovirus (EV) detection and genotyping were performed directly from clinical samples. From 4,080 clinical specimens 25 EV types were identified with a median age of patients of 5 years and 68% of all cases affected children aged 10 years or younger, although infections occurred in all age-groups. In 130 cases neurological symptoms were recorded, in 123 cases the infection presented in skin related signs including hand, foot, and mouth disease (HFMD), herpangina and rash. In 2010 EV-A71 was found to cause the majority of diagnosed EV infections while in 2011 and from 2014-2018, Coxsackievirus (CV)-A6 was identified most often. Echovirus E6 accounted for the most cases in 2012 and Echovirus 30 dominated in 2013. EV-D68 was identified only in 2010 and 2013.Widespread circulation of several EV-A and EV-B viruses with occasional occurrence of EV-C and EV-D was detected. The ability of EVs to cause severe infections in sporadic cases and regular outbreaks highlight the importance of continued monitoring of circulating EV types.

A Novel Surface-Exposed Polypeptide Is Successfully Employed as a Target for Developing a Prototype One-Step Immunochromatographic Strip for Specific and Sensitive Direct Detection of Staphylococcus aureus Causing Neonatal Sepsis

Neonatal sepsis is a life-threatening condition and Staphylococcus aureus is one of its major causes. However, to date, no rapid and sensitive diagnostic tool has been developed for its direct detection. Bioinformatics analyses identified a surface-exposed 112-amino acid polypeptide of the cell wall protein NWMN_1649, a surface protein involved in cell aggregation and biofilm formation, as being a species-specific and highly conserved moiety. The polypeptide was cloned, purified, and used to immunize mice to raise specific immunoglobulins. The purified antibodies were conjugated to gold nano-particles and used to assemble an immunochromatographic strip (ICS). The developed prototype ICS detected as low as 5 µg purified polypeptide and 102 CFU/mL S. aureus within 15 min. The strip showed superior ability to directly detect S. aureus in neonatal sepsis blood specimens without prior sample processing. Moreover, it showed no cross-reaction in specimens infected with two other major causes of neonatal sepsis; coagulase-negative staphylococci and Klebsiella pneumoniae. The selected NWMN_1649-derived polypeptide demonstrates success as a promising biomolecule upon which a prototype ICS has been developed. This ICS provides a rapid, direct, sensitive, and specific option for the detection of S. aureus causing neonatal sepsis. Such a tool is urgently needed especially in resources-limited countries.

Performance of PCR/Electrospray Ionization-Mass Spectrometry on Whole Blood for Detection of Bloodstream Microorganisms in Patients with Suspected Sepsis

Blood culture (BC) often fails to detect bloodstream microorganisms in sepsis. However, molecular diagnostics hold great potential. The molecular method PCR/electrospray ionization-mass spectrometry (PCR/ESI-MS) can detect DNA from hundreds of different microorganisms in whole blood. The aim of the present study was to evaluate the performance of this method in a multicenter study including 16 teaching hospitals in the United States (n = 13) and Europe (n = 3). First, on testing of 2,754 contrived whole blood samples, with or without spiked microorganisms, PCR/ESI-MS produced 99.1% true-positive and 97.2% true-negative results. Second, among 1,460 patients with suspected sepsis (sepsis-2 definition), BC and PCR/ESI-MS on whole blood were positive in 14.6% and 25.6% of cases, respectively, with the following result combinations: BC positive and PCR/ESI-MS negative, 4.3%; BC positive and PCR/ESI-MS positive, 10.3%; BC negative and PCR/ESI-MS positive, 15.3%; and BC negative and PCR/ESI-MS negative, 70.1%. Compared with BC, PCR/ESI-MS showed the following sensitivities (coagulase-negative staphylococci not included): Gram-positive bacteria, 58%; Gram-negative bacteria, 78%; and Candida species, 83%. The specificities were >94% for all individual species. Patients who had received prior antimicrobial medications (n = 603) had significantly higher PCR/ESI-MS positivity rates than patients without prior antimicrobial treatment-31% versus 22% (P < 0.0001)-with pronounced differences for Gram-negative bacteria and Candida species. In conclusion, PCR/ESI-MS showed excellent performance on contrived samples. On clinical samples, it showed high specificities, moderately high sensitivities for Gram-negative bacteria and Candida species, and elevated positivity rates during antimicrobial treatment. These promising results encourage further development of molecular diagnostics to be used with whole blood for detection of bloodstream microorganisms in sepsis.

Spectrally efficient optical orthogonal frequency division multiplexing

This paper charts the development of spectrally efficient forms of optical orthogonal frequency division multiplexing (OFDM) that are suited for intensity-modulated direct detection systems, such as wireless optical communications. The journey begins with systems using a DC-bias to ensure that no parts of the signal that modulates the optical source are negative in value, as negative optical intensity is unphysical. As the DC-part of the optical signal carries no information, it is wasteful in energy; thus asymmetrically clipped optical OFDM was developed, removing any negative-going peaks below the mean. Unfortunately, the clipping causes second-order distortion and intermodulation, so some subcarriers appear to be unusable, halving spectral efficiency; this is similar for unipolar and flipped optical OFDM. Thus, a considerable effort has been made to regain spectral efficiency, using layered techniques where the clipping distortion is mostly cancelled at the receiver, from a knowledge of one unpolluted layer, enabling one or more extra 'layers/paths/depths' to be received on the previously unusable subcarriers. Importantly, for a given optical power and high-order modulation, layered methods offer the best spectral efficiencies and need the lowest signal-to-noise ratios, especially if diversity combining is used. Thus, they could be important for high-bandwidth optical fibre systems. Efficient methods of generating all layers simultaneously, using fast Fourier transforms with their partial calculations extracted, are discussed, as are experimental demonstrations in both wireless and short-haul communications links. A musical analogy is also provided, which may point to how orchestral and rock music is deciphered in the brain. This article is part of the theme issue 'Optical wireless communication'.

Specific detection of Trichophyton rubrum and Trichophyton interdigitale based on loop-mediated isothermal amplification (LAMP) from onychomycosis specimens

In diagnosing onychomycosis, diseases with similar features must be excluded by demonstrating the presence of fungal infection and identifying the fungal species. However, fungal culture of onychomycosis-derived samples usually takes many weeks to yield species identification results, and is associated with a low successful culture rate. Loop-mediated isothermal amplification (LAMP) is a highly sensitive and specific molecular biological method that can amplify DNA at a constant temperature, allowing for a simpler testing procedure, shorter detection time and less cost than conventional techniques including quantitative polymerase chain reaction. We have developed a new LAMP method specifically to detect Trichophyton rubrum (T. rubrum) and Trichophyton interdigitale (T. interdigitale), major causative dermatophytes for onychomycosis, and analyzed the correlation between LAMP results and those of the existing fungal culture method for the detection and identification of Trichophyton species from onychomycosis-derived samples. The results showed that all 59 specimens in which T. rubrum or T. interdigitale was identified by fungal culture also tested positive by LAMP, giving a 100% positivity concordance rate between the two methods. Moreover, all 55 and four specimens in which T. rubrum and T. interdigitale were identified by fungal culture, respectively, also tested positive for each species by LAMP, again giving a 100% species-identification concordance rate. The high correlation demonstrated between LAMP and fungal culture results in detection and identification of Trichophyton species from onychomycosis-derived samples suggests high reliability of LAMP as a promising, alternative mycological detection and identification technique which can serve as an alternative to the fungal culture method.

Single Core Genome Sequencing for Detection of both Borrelia burgdorferi Sensu Lato and Relapsing Fever Borrelia Species

Lyme disease, initially described as Lyme arthritis, was reported before nucleic-acid based detection technologies were available. The most widely used diagnostic tests for Lyme disease are based on the serologic detection of antibodies produced against antigens derived from a single strain of Borrelia burgdorferi. The poor diagnostic accuracy of serological tests early in the infection process has been noted most recently in the 2018 Report to Congress issued by the U.S. Department of Health and Human Services Tick-Borne Disease Working Group. Clinical Lyme disease may be caused by a diversity of borreliae, including those classified as relapsing fever species, in the United States and in Europe. It is widely accepted that antibiotic treatment of Lyme disease is most successful during this critical early stage of infection. While genomic sequencing is recognized as an irrefutable direct detection method for laboratory diagnosis of Lyme borreliosis, development of a molecular diagnostic tool for all clinical forms of borreliosis is challenging because a “core genome” shared by all pathogenic borreliae has not yet been identified. After a diligent search of the GenBank database, we identified two highly conserved segments of DNA sequence among the borrelial 16S rRNA genes. We further developed a pair of Borrelia genus-specific PCR primers for amplification of a segment of borrelial 16S rRNA gene as a “core genome” to be used as the template for routine Sanger sequencing-based metagenomic direct detection test. This study presented examples of base-calling DNA sequencing electropherograms routinely generated in a clinical diagnostic laboratory on DNA extracts of human blood specimens and ticks collected from human skin bites and from the environment. Since some of the tick samples tested were collected in Ireland, borrelial species or strains not known to exist in the United States were also detected by analysis of this 16S rRNA “core genome”. We recommend that hospital laboratories located in Lyme disease endemic areas begin to use a “core genome” sequencing test to routinely diagnose spirochetemia caused by various species of borreliae for timely management of patients at the early stage of infection.

Unique Structural Characteristics of Catalytic Palladium/Gold Nanoparticles on Graphene

Adding Au to Pd nanoparticles (NPs) can impart high catalytic activity with respect to hydrogenation of a wide range of substances. These materials are often synthesized by reducing metallic precursors; hence, sonochemical and solvothermal processes are commonly used to anchor these bimetals onto thin supports, including graphene. Although similar NPs have been studied reasonably well, a clear understanding of structural characteristics relative to their synthesis parameters is lacking, due to limitations in characterization techniques, which may prevent optimization of this very promising catalyst. In this report, a strategic approach has been used to identify this structural and material synthesis correlation, starting with controlled sample preparation and followed by detailed characterization. This includes advanced scanning transmission electron microscopy and electron energy loss spectroscopy; the latter using a state-of-the-art instrumentation to map the distribution of Pd and Au, and to identify chemical state of the Pd NPs, which has not been previously reported. Results show that catalytic bimetal NP clusters were made of small zero-valent Pd NPs aggregating to form a shell around an Au core. Not only can the described characterization approach be applied to similar material systems, but the results can guide the optimization of the synthesis procedures.

dCas9-mediated Nanoelectrokinetic Direct Detection of Target Gene for Liquid Biopsy

The-state-of-the-art bio- and nanotechnology have opened up an avenue to noninvasive liquid biopsy for identifying diseases from biomolecules in bloodstream, especially DNA. In this work, we combined sequence-specific-labeling scheme using mutated clustered regularly interspaced short palindromic repeats associated protein 9 without endonuclease activity (CRISPR/dCas9) and ion concentration polarization (ICP) phenomenon as a mechanism to selectively preconcentrate targeted DNA molecules for rapid and direct detection. Theoretical analysis on ICP phenomenon figured out a critical mobility, elucidating two distinguishable concentrating behaviors near a nanojunction, a stacking and a propagating behavior. Through the modulation of the critical mobility to shift those behaviors, the C-C chemokine receptor type 5 ( CCR5) sequences were optically detected without PCR amplification. Conclusively, the proposed dCas9-mediated genetic detection methodology based on ICP would provide rapid and accurate micro/nanofluidic platform of liquid biopsies for disease diagnostics.

Detection of Carbapenemase-Producing Enterobacteriaceae in Positive Blood Culture Using an Immunochromatographic RESIST-4 O.K.N.V. Assay

We evaluated the performance of the RESIST-4 O.K.N.V. assay (Coris) with 98 isolates to detect OXA-48-like and KPC-, NDM-, and VIM-type carbapenemases directly on positive human blood cultures. OXA-48-like and KPC-type isolates were correctly detected, but the detection of NDM- and VIM-type carbapenemases was weak and variable. We show that repeating the test on a 4-h subculture improves the detection of NDM- and VIM-type carbapenemases to 100%.

Environmental Surveillance Reveals Complex Enterovirus Circulation Patterns in Human Populations

Background

Enteroviruses are common human pathogens occasionally associated with severe disease, notoriously paralytic poliomyelitis caused by poliovirus. Other enterovirus serotypes such as enterovirus A71 and D68 have been linked to severe neurological syndromes. New enterovirus serotypes continue to emerge, some believed to be derived from nonhuman primates. However, little is known about the circulation patterns of many enterovirus serotypes and, in particular, the detailed enterovirus composition of sewage samples.

Methods

We used a next-generation sequencing approach analyzing reverse transcriptase polymerase chain reaction products synthesized directly from sewage concentrates.

Results

We determined whole-capsid genome sequences of multiple enterovirus strains from all 4 A to D species present in environmental samples from the United Kingdom, Senegal, and Pakistan.

Conclusions

Our results indicate complex enterovirus circulation patterns in human populations with differences in serotype composition between samples and evidence of sustained and widespread circulation of many enterovirus serotypes. Our analyses revealed known and divergent enterovirus strains, some of public health relevance and genetically linked to clinical isolates. Enteroviruses identified in sewage included vaccine-derived poliovirus and enterovirus D-68 stains, new enterovirus A71 and coxsackievirus A16 genogroups indigenous to Pakistan, and many strains from rarely reported serotypes. We show how this approach can be used for the early detection of emerging pathogens and to improve our understanding of enterovirus circulation in humans.

Detection by Direct Next Generation Sequencing Analysis of Emerging Enterovirus D68 and C109 Strains in an Environmental Sample From Scotland

Background: Human enteroviruses (EVs) have been linked with severe disease and syndromes as varied as acute respiratory illness, myocarditis, and flaccid paralysis. With global polio eradication on sight the focus of clinical investigations has expanded to the identification of other EV serotypes associated with severe neurological conditions such as EV-D68, responsible for large outbreaks in 2014 and 2016 that spread worldwide and were related with severe respiratory disease leading to acute myelitis in some cases. New EV serotypes with epidemic potential continue to emerge such as EV-C104, EV-C105, EV-C109, and EV-C117 identified in respiratory samples in recent years.

Methods: We used a next generation sequencing (NGS) approach to detect multiple EV serotypes directly in a sewage concentrate from Glasgow (Scotland, United Kingdom) generating whole-capsid nucleotide sequences that were compared to sequences of cell culture isolates from this sewage sample and clinical EV isolates from GenBank.

Results: Thirteen different serotypes belonging to all four A, B, C, and D EV species were identified in the sewage concentrate. EV strains closely related to EV-D68 epidemic isolates of B3 lineage reported in the United States and Europe in 2016 and to EV-C109 respiratory isolates found in Denmark and Netherlands in 2015 were identified.

Conclusion: Environmental surveillance (ES) can effectively detect EV circulation in human populations. The use of NGS for ES can help overcoming the limitations of traditional cell culture and sequencing methods, which are selective and biased, and can contribute to the early detection and assessment of spread of emerging EV pathogens.

A Direct Bicarbonate Detection Method Based on a Near-Concentric Cavity-Enhanced Raman Spectroscopy System

Raman spectroscopy has great potential as a tool in a variety of hydrothermal science applications. However, its low sensitivity has limited its use in common sea areas. In this paper, we develop a near-concentric cavity-enhanced Raman spectroscopy system to directly detect bicarbonate in seawater for the first time. With the aid of this near-concentric cavity-enhanced Raman spectroscopy system, a significant enhancement in HCO₃⁻ detection has been achieved. The obtained limit of detection (LOD) is determined to be 0.37 mmol/L—much lower than the typical concentration of HCO₃⁻ in seawater. By introducing a specially developed data processing scheme, the weak HCO₃⁻ signal is extracted from the strong sulfate signal background, hence a quantitative analysis with R² of 0.951 is made possible. Based on the spectra taken from deep sea seawater sampling, the concentration of HCO₃⁻ has been determined to be 1.91 mmol/L, with a relative error of 2.1% from the reported value (1.95 mmol/L) of seawater in the ocean. It is expected that the near-concentric cavity-enhanced Raman spectroscopy system could be developed and used for in-situ ocean observation in the near future.

Direct Detection of Nucleic Acid with Minimizing Background and Improving Sensitivity Based on a Conformation-Discriminating Indicator

As is well-known, the nucleic acid indicator-based strategy is one of the major approaches to monitor the nucleic acid hybridization-mediated recognition events in biochemical analysis, displaying obvious advantages including simplicity, low cost, convenience, and generality. However, conventional indicators either hold strong self-fluorescence or can be lighted by both ssDNA and dsDNA, lacking absolute selectivity for a certain conformation, always with high background interference and low sensitivity in sensing; and additional processing (e.g., nanomaterial-mediated background suppression, and enzyme-catalyzed signal amplification) is generally required to improve the detection performance. In this work, a carbazole derivative, EBCB, has been synthesized and screened as a dsDNA-specific fluorescent indicator. Compared with conventional indicators under the same conditions, EBCB displayed a much higher selective coefficient for dsDNA, with little self-fluorescence and negligible effect from ssDNA. Based on its superior capability in DNA conformation-discrimination, high sensitivity with minimizing background interference was demonstrated for direct detection of nucleic acid, and monitoring nucleic acid-based circuitry with good reversibity, resulting in low detection limit and high capability for discriminating base-mismatching. Thus, we expect that this highly specific DNA conformation-discriminating indicator will hold good potential for application in biochemical sensing and molecular logic switching.

Quantitative multiplexed-tandem PCR for direct detection of bacteraemia in critically ill patients

Culture remains the gold standard for diagnosis of blood stream infections (BSI), but its clinical utility is limited by slow turnaround times. Here we describe a method for rapid quantitative detection of bacterial DNA directly extracted from whole blood using a multiplexed tandem real-time PCR (MT-PCR) assay targeting Staphylococcus, Streptococcus, Pseudomonas, Enterococcus and Enterobacteriaceae 16S rDNA genes. Results were available less than 3.5 hours after blood collection with all five bacterial targets having limits of detection between 10¹ and 10³ CFU/mL. A small-scale clinical evaluation of the assay using blood samples collected from 15 patients admitted to the Intensive Care Unit at our institution demonstrated 93.3% (14/15) concordance between MT-PCR and blood culture when detection of persistent bacterial DNAemia by MT- PCR was considered a true result. Further evaluation with clinical samples is needed; however, this method has potential as an effective rule-in diagnostic tool for bacteraemic sepsis and septic shock.

Occurrence and Diversity of Clinically Important Vibrio Species in the Aquatic Environment of Georgia

Among the more than 70 different Vibrio species inhabiting marine, estuarine, and freshwater ecosystems, 12 are recognized as human pathogens. The warm subtropical climate of the Black Sea coastal area and inland regions of Georgia likely provides a favorable environment for various Vibrio species. From 2006 to 2009, the abundance, ecology, and diversity of clinically important Vibrio species were studied in different locations in Georgia and across seasons. Over a 33-month period, 1,595 presumptive Vibrio isolates were collected from the Black Sea (n = 657) and freshwater lakes around Tbilisi (n = 938). Screening of a subset of 440 concentrated and enriched water samples by PCR-electrospray ionization/mass spectrometry (PCR-ESI/MS) detected the presence of DNA from eight clinically important Vibrio species: V. cholerae, V. parahaemolyticus, V. vulnificus, V. mimicus, V. alginolyticus, V. harveyi, V. metschnikovii, and V. cincinnatiensis. Almost 90% of PCR/ESI-MS samples positive for Vibrio species were collected from June through November. Three important human-pathogenic Vibrio species (V. cholerae, V. parahaemolyticus, and V. vulnificus) were detected in 62.8, 37.8, and 21.4% of samples testing positive for Vibrios, respectively. The results of these activities suggest that natural reservoirs for human-pathogenic Vibrios exist in Georgian aquatic environments. Water temperature at all sampling sites was positively correlated with the abundance of clinically important Vibrio spp. (except V. metschnikovii), and salinity was correlated with species composition at particular Black Sea sites as well as inland reservoirs.

Improved SERS Nanoparticles for Direct Detection of Circulating Tumor Cells in the Blood

The detection of circulating tumor cells (CTCs) in the blood of cancer patients is crucial for early cancer diagnosis, cancer prognosis, evaluation of the treatment effect of chemotherapy drugs, and choice of cancer treatment options. In this study, we propose new surface-enhanced Raman scattering (SERS) nanoparticles for the direct detection of CTCs in the blood. Under the optimized experimental conditions, our SERS nanoparticles exhibit satisfying performances for the direct detection of cancer cells in the rabbit blood. A good linear relationship is obtained between the SERS intensity and the concentration of cancer cells in the range of 5-500 cells/mL (R(2) = 0.9935), which demonstrates that the SERS nanoparticles can be used for the quantitative analysis of cancer cells in the blood and the limit of detection is 5 cells/mL, which is lowest compared with the reported values. The SERS nanoparticles also have an excellent specificity for the detection of cancer cells in the rabbit blood. The above results reinforce that our SERS nanoparticles can be used for the direct detection of CTCs in the blood with excellent specificity and high sensitivity.

Detection of undistorted continuous wave (CW) electron paramagnetic resonance (EPR) spectra with non-adiabatic rapid sweep (NARS) of the magnetic field

A continuous wave (CW) electron paramagnetic resonance (EPR) spectrum is typically displayed as the first harmonic response to the application of 100 kHz magnetic field modulation, which is used to enhance sensitivity by reducing the level of 1/f noise. However, magnetic field modulation of any amplitude causes spectral broadening and sacrifices EPR spectral intensity by at least a factor of two. In the work presented here, a CW rapid-scan spectroscopic technique that avoids these compromises and also provides a means of avoiding 1/f noise is developed. This technique, termed non-adiabatic rapid sweep (NARS) EPR, consists of repetitively sweeping the polarizing magnetic field in a linear manner over a spectral fragment with a small coil at a repetition rate that is sufficiently high that receiver noise, microwave phase noise, and environmental microphonics, each of which has 1/f characteristics, are overcome. Nevertheless, the rate of sweep is sufficiently slow that adiabatic responses are avoided and the spin system is always close to thermal equilibrium. The repetitively acquired spectra from the spectral fragment are averaged. Under these conditions, undistorted pure absorption spectra are obtained without broadening or loss of signal intensity. A digital filter such as a moving average is applied to remove high frequency noise, which is approximately equivalent in bandwidth to use of an integrating time constant in conventional field modulation with lock-in detection. Nitroxide spectra at L- and X-band are presented.

Deconvolution of sinusoidal rapid EPR scans

In rapid scan EPR the magnetic field is scanned through the signal in a time that is short relative to electron spin relaxation times. Previously it was shown that the slow-scan lineshape could be recovered from triangular rapid scans by Fourier deconvolution. In this paper a general Fourier deconvolution method is described and demonstrated to recover the slow-scan lineshape from sinusoidal rapid scans. Since an analytical expression for the Fourier transform of the driving function for a sinusoidal scan was not readily apparent, a numerical method was developed to do the deconvolution. The slow scan EPR lineshapes recovered from rapid triangular and sinusoidal scans are in excellent agreement for lithium phthalocyanine, a trityl radical, and the nitroxyl radical, tempone. The availability of a method to deconvolute sinusoidal rapid scans makes it possible to scan faster than is feasible for triangular scans because of hardware limitations on triangular scans.

Direct detection of the biological toxin in acidic environment by electrochemical impedimetric immunosensor

This study describes the direct detection of the biological toxin (Ricin) in acidic environment without pH adjustment by hydrophobically modified electrochemical impedance immunosensor (EII). The nano-porous aluminum substrate for EII was hydrophobically modified via self-assembled monolayer (SAM) of APTES. Biosensor for the detection of the Ricin was fabricated by the covalent cross-linking of antibody (Ab) with APTES-SAM. The immunoreactions between the immobilized Ab and the biological toxin in several diagnostic solutions were monitored by the electrochemical impedance spectroscopy (EIS) under the polarization of EII versus reference electrode. EII could detect the presence of the biological toxin in acidic foods in 20 mins without pH adjustment. The negatively charged ions including hydroxides would be adsorbed on the hydrophobic body of APTES-SAMs by the polarization during EIS analysis, and offset the effect of acids on the immunological activity of the immobilized Ab. It suggested that the adsorption of negatively charged ions helped to keep the immunological activities of the immobilized Ab on EII in acidic environment. Proposed mechanism of the localized pH adjustment that makes possible immunoreaction occurrence in low pH sample matrix is briefly discussed.

A new strategy for fast radiofrequency CW EPR imaging: direct detection with rapid scan and rotating gradients

Rapid field scan on the order of T/s using high frequency sinusoidal or triangular sweep fields superimposed on the main Zeeman field, was used for direct detection of signals without low-frequency field modulation. Simultaneous application of space-encoding rotating field gradients have been employed to perform fast CW EPR imaging using direct detection that could, in principle, approach the speed of pulsed FT EPR imaging. The method takes advantage of the well-known rapid-scan strategy in CW NMR and EPR that allows arbitrarily fast field sweep and the simultaneous application of spinning gradients that allows fast spatial encoding. This leads to fast functional EPR imaging and, depending on the spin concentration, spectrometer sensitivity and detection band width, can provide improved temporal resolution that is important to interrogate dynamics of spin perfusion, pharmacokinetics, spectral spatial imaging, dynamic oxymetry, etc.

Filter Transmittance Measurements in the Infrared

We have set up a novel direct detection system to measure filter transmittances over an attenuation range of at least 5 decades, with relative combined standard uncertainties as low as 0.5% (1σ) per decade, in the 9 μm to 11 μm spectral region. This system, using an apparatus originally designed for a heterodyne measurement of transmittance, achieves higher accuracy at the expense of a reduced dynamic range. This independent measurement of transmittance allows verification of the heterodyne technique. Our system uses a source modulated at 30 MHz and a specially constructed high dynamic range and high accuracy lock-in amplifier capable of operation at the modulation frequency. The high modulation frequency and narrow bandwidth of the system allow thermal background radiation to be suppressed and high accuracy to be achieved. We correct for the non-ideal natures of the detector and attenuators. In particular, the detector position is scanned to reduce the effect of its spatial nonuniformity and the deflection of the transmitted beam caused by the nonparallel surfaces of the filter. We discuss the sources of systematic errors and the methodology to reduce their contribution.