Carbapenem-resistant hypervirulent ST23 Klebsiella pneumoniae with a highly transmissible dual-carbapenemase plasmid in Chile.

BACKGROUND: The convergence of hypervirulence and carbapenem resistance in the bacterial pathogen Klebsiella pneumoniae represents a critical global health concern. Hypervirulent K. pneumoniae (hvKp) strains, frequently from sequence type 23 (ST23) and having a K1 capsule, have been associated with severe community-acquired invasive infections. Although hvKp were initially restricted to Southeast Asia and primarily antibiotic-sensitive, carbapenem-resistant hvKp infections are reported worldwide. Here, within the carbapenemase production Enterobacterales surveillance system headed by the Chilean Public Health Institute, we describe the isolation in Chile of a high-risk ST23 dual-carbapenemase-producing hvKp strain, which carbapenemase genes are encoded in a single conjugative plasmid. RESULTS: Phenotypic and molecular tests of this strain revealed an extensive resistance to at least 15 antibiotic classes and the production of KPC-2 and VIM-1 carbapenemases. Unexpectedly, this isolate lacked hypermucoviscosity, challenging this commonly used hvKp identification criteria. Complete genome sequencing and analysis confirmed the K1 capsular type, the KpVP-1 virulence plasmid, and the GIE492 and ICEKp10 genomic islands carrying virulence factors strongly associated with hvKp. Although this isolate belonged to the globally disseminated hvKp clonal group CG23-I, it is unique, as it formed a clade apart from a previously reported Chilean ST23 hvKp isolate and acquired an IncN KPC-2 plasmid highly disseminated in South America (absent in other hvKp genomes), but now including a class-I integron carrying blaVIM-1 and other resistance genes. Notably, this isolate was able to conjugate the double carbapenemase plasmid to an E. coli recipient, conferring resistance to 1st -5th generation cephalosporins (including combinations with beta-lactamase inhibitors), penicillins, monobactams, and carbapenems. CONCLUSIONS: We reported the isolation in Chile of high-risk carbapenem-resistant hvKp carrying a highly transmissible conjugative plasmid encoding KPC-2 and VIM-1 carbapenemases, conferring resistance to most beta-lactams. Furthermore, the lack of hypermucoviscosity argues against this trait as a reliable hvKp marker. These findings highlight the rapid evolution towards multi-drug resistance of hvKp in Chile and globally, as well as the importance of conjugative plasmids and other mobile genetic elements in this convergence. In this regard, genomic approaches provide valuable support to monitor and obtain essential information on these priority pathogens and mobile elements.

Caracterización fenotípica y molecular de cepas de Klebsiella pneumoniae productores de carbapenemasas tipo OXA-48 circulantes en Chile / Phenotypic and molecular characterization of OXA-48 like producing Klebsiella pneumoniae isolates in Chile

INTRODUCCIÓN: La aparición y diseminación de Enterobacterales resistentes a carbapenémicos ha generado un gran impacto en las infecciones asociadas a la atención de salud en el mundo. Recientemente, en Chile se detectó un brote por Klebsiella pneumoniae productora de carbapenemasas tipo oxacilinasas (OXA) de la subfamilia tipo OXA-48, reportándose los primeros casos en pacientes hospitalizados mayoritariamente en la zona norte del país. OBJETIVO: Determinar los perfiles fenotípicos, genotípicos y de susceptibilidad antimicrobiana de 16 cepas referidas durante mayo del año 2021 desde las regiones de Antofagasta y Metropolitana al Laboratorio de Referencia del Instituto de Salud Pública. METODOLOGÍA: Las cepas provenientes de muestras clínicas fueron analizadas mediante técnicas tradicionales (Kirby-Bauer y epsilometría) y automatizadas, además de técnicas colorimétricas, inmunocromatográficas y moleculares (RPC y PFGE). Resultados: Se detectó la presencia de los genes blaoxa-48 y blaoxa-232 con una resistencia inusual, tanto a carbapenémicos (ertapenem, imipenem y meropenem) como a cefalosporinas (cefepime, cefotaxima y ceftazidima), además de piperacilina/tazobactam y temocilina. Se detectaron dos subtipos por PFGE, siendo predominante el clon CL-Kpn-Spe-329 (93,8%) con dos mecanismos de resistencia identificados: carbapenemasa y β-lactamasa de espectro extendido (BLEE). CONCLUSIÓN: Ante esta alerta epidemiológica es necesario unificar criterios existentes en la red asistencial nacional para la oportuna detección, vigilancia y control de posibles brotes de cepas productores de oxacilinasa tipo OXA-48.

BACKGROUND: The appearance and spread of carbapenems-resistant Enterobacterales have generated a major impact on health care-associated infections worldwide. Recently, a Klebsiella pneumoniae outbreak expressing OXA-48 like-carbapenemases was detected in Chile, the first reported cases corresponded to hospitalized patients mainly from northern Chile. AIM: To characterize the phenotypic and genotypic profiles of antimicrobial susceptibility of 16 clinical isolates referred during May 2021 from Antofagasta and Metropolitan regions to the Reference Laboratory of Instituto de Salud Publica. METHODS: Antimicrobial susceptibility of all strains was analyzed using traditional (Kirby-Bauer and epsilometry) and automated methods, and complemented with colorimetric, immunochromatographic and molecular (PCR and PFGE) techniques. RESULTS: As a result of the genetic characterization, blaoxa-48 and blaoxa-232 genes were detected, showing the isolates an unusual resistance profile to both carbapenems (ertapenem, imipenem, and meropenem) and cephalosporins (cefepime, cefotaxime, and ceftazidine), as well as piperacillin/ tazobactam and temocillin. Two subtypes were detected by PFGE, with a predominant clone CL-Kpn-Spe-329 (93.8%), with two resistance mechanisms identified: carbapenemase and extended-spectrum β-lactamase (ESBL). CONCLUSION: Due to this epidemiological alert, it is essential the establishment of national guidelines for early detection, surveillance, and control of future outbreaks of OXA-48 like carbapenemases isolates.

National Seroprevalence of Coxiella burnetii in Chile, 2016-2017.

Coxiella burnetii is an intracellular bacterium and the cause of the zoonotic infection, Q fever. National surveillance data on C. burnetii seroprevalence is currently not available for any South American country, making efforts of public health to implement strategies to mitigate infections in different at-risk groups within the population extremely challenging. In the current study, we used two commercial anti-C. burnetii immunoassays to screen sera collected from a sample of the Chilean population as part of a 2016-2017 national health survey (n = 5166), nationwide and age-standardized. The seroprevalence for C. burnetii for persons ≥ 15 years was estimated to be 3.0% (95% CI 2.2-4.0), a level similar to national surveys from The Netherlands (2.4%) and USA (3.1%), but lower than Australia (5.6%). A linear increase of C. burnetii seropositivity was associated with an individual's age, with the peak seroprevalence 5.6% (95% CI 3.6-8.6) observed in the ≥65 years' group. C. burnetii seropositivity was significantly higher in the southern macro-zone 6.0% (95% CI 3.3-10.6) compared to metropolitan region 1.8% (95% CI 0.9-3.3), the former region being home to significant livestock industries, particularly dairy farming. These data will be useful to inform targeted strategies for the prevention of Q fever in at-risk populations in Chile.

Evidence of Q Fever and Rickettsial Disease in Chile.

Q fever and rickettsial diseases occur throughout the world and appear to be emergent zoonoses in Chile. The diagnosis of these diseases is currently uncommon in Chile, as their clinical presentations are non-specific and appropriate diagnostic laboratory assays are of limited availability. During a recent outbreak of undiagnosed human atypical pneumonia, we serologically investigated a series of 357 cases from three regions of southern Chile. The aim was to identify those caused by Coxiella burnetii and/or Rickettsia spp. Serological analysis was performed by ELISA and an immunofluorescence assay (IFA) for acute and convalescence sera of patients. Our results, including data from two international reference laboratories, demonstrate that 71 (20%) of the cases were Q fever, and 44 (15%) were a likely rickettsial infection, although the rickettsial species could not be confirmed by serology. This study is the first report of endemic Q fever and rickettsial disease affecting humans in Chile.

Structural characterization of Au nano bipyramids: reshaping under thermal annealing, the capping agent effect and surface decoration with Pt.

Anisotropic gold nanoparticles offer potential applications due to their functionalities and shape-dependent properties. Reshaping noble metal nanoparticles is an interesting field with optical, surface-enhanced Raman spectroscopy, catalytic applications and potential application as a photothermic therapy. This work comprises a structural study on gold nano bipyramids (Au NBPs) and nanodumbbells, and the evolution of Au NBPs capped with cetyltrimethylammonium bromide and dodecanethiol through an in situ and ex situ heating process in high vacuum. Also, we study the reshaping of Au NBPs by the addition of Pt to study the surface modification and the strain generated on a single particle by geometric phase analysis.

Exploring weak intermolecular interactions in thiocyanate-bonded Zn(ii) and Cd(ii) complexes with methylimidazole: crystal structures, Hirshfeld surface analysis and luminescence properties.

Four new thiocyanate-Zn(ii) and -Cd(ii) complexes with 1-methylimidazole (1-MeIm) and 2-methylimidazole (2-MeIm), namely, Zn(1-MeIm)2(SCN)2 (1), Zn(2-MeIm)2(SCN)2 (2), Cd(1-MeIm)4(SCN)2 (3) and polymeric [Cd(2-MeIm)2(SCN)2] n (4), have been synthesized and characterized by IR, Raman and UV-Vis spectroscopy. The thermal behavior for all complexes was evaluated by thermo-gravimetric analysis and differential thermal analysis. The crystal structures of complexes 1-4 were solved by single-crystal X-ray diffraction methods. A study of intermolecular interactions in the solid state compounds revealed that molecules are linked by weak N-H⋯S and C-H⋯S hydrogen bonds and also by C-H⋯π interaction in the case of structures 2-4, which are responsible for the formation and stability of the molecular assemblies. Hirshfeld surfaces and 2D-fingerprint plots allowed us to visualize the intermolecular contacts and their relative contributions to the total surface for each compound. A comparative analysis against similar halogen-bonded complexes was carried out to investigate the tendency of inter-molecular interactions to form contacts in crystals by using the enrichment ratio descriptor. The emission spectra of the free imidazole derivatives and their Zn(ii) and Cd(ii) complexes were recorded in acetonitrile solutions. The emissions observed in the spectra of complexes were ascribed to the intra-ligand transitions and ligand-to-metal charge transfer and we have observed an interesting correlation between the fluorescence intensities and C-H⋯π interactions.

Risk Factors and Outcomes of Patients Requiring a Permanent Pacemaker After Aortic Valve Replacement in the United States.

INTRODUCTION: The need for permanent pacemaker implantation (PCM) following surgical aortic valve replacement (SAVR) is uncommon but can lead to increased hospital resource utilization. Using nationwide data, we sought to (1) identify hospital, patient, and procedure-level risk factors for PCM after SAVR and (2) determine incremental resource utilization. METHODS: We identified 659,692 patients from the Nationwide Inpatient Sample database who underwent SAVR with or without coronary artery bypass grafting (CABG), mitral valvuloplasty (MVr), or mitral valve replacement (MVR) between 1998 and 2009. Patients with pre-existing pacemakers, a concomitant Maze procedure, or endocarditis were excluded. Multivariable regression analysis and propensity matching were used for comparisons of outcomes and costs. RESULTS: Overall prevalence of PCM was 5.1% (n = 34,020; SAVR alone, 4.8%; SAVR + CABG, 4.6%; SAVR + MVr, 7.7%; SAVR + MVR, 10%). Important risk factors for PCM after SAVR were coexisting comorbidities, older age, and addition of mitral valve surgery. Hospital volume and teaching status, location, race, and sex were not associated with PCM. Among matched pairs, patients requiring PCM had lower in-hospital mortality (3.1% vs. 6.4%, p < 0.001) but longer median length of stay (12 vs. 9 days, p < 0.001) and higher hospital costs ($50,000 vs. $37,000, p < 0.001), and they were less likely to be discharged home (33% vs. 36%, p < 0.001). Factors associated with later PCM (postoperative day ≥6) included SAVR + MVR, female sex, fewer comorbidities, northeastern region, and higher hospital volume. Median hospital costs were greater ($57,000 vs. $48,000, p < 0.001) among patients whose pacemakers were implanted later. CONCLUSIONS: PCM following SAVR is associated with lower hospital mortality, but increased cost and length of stay. doi: 10.1111/jocs.12769 (J Card Surg 2016;31:476-485).

It is Time to Ban Rapid Weight Loss from Combat Sports.

Most competitions in combat sports are divided into weight classes, theoretically allowing for fairer and more evenly contested disputes between athletes of similar body size, strength and agility. It has been well documented that most athletes, regardless of the combat sports discipline, reduce significant amounts of body weight in the days prior to competition to qualify for lighter weight classes. Rapid weight loss is characterised by the reduction of a significant amount of body weight (typically 2-10 %, although larger reductions are often seen) in a few days prior to weigh-in (mostly in the last 2-3 days) achieved by a combination of methods that include starvation, severe restriction of fluid intake and intentional sweating. In doing so, athletes try to gain a competitive advantage against lighter, smaller and weaker opponents. Such a drastic and rapid weight reduction is only achievable via a combination of aggressive strategies that lead to hypohydration and starvation. The negative impact of these procedures on health is well described in the literature. Although the impact of rapid weight loss on performance is debated, there remains robust evidence showing that rapid weight loss may not impair performance, and translates into an actual competitive advantage. In addition to the health and performance implications, rapid weight loss clearly breaches fair play and stands against the spirit of the sport because an athlete unwilling to compete having rapidly reduced weight would face unfair contests against opponents who are 'artificially' bigger and stronger. The World Anti-Doping Agency Code states that a prohibited method must meet at least two of the following criteria: (1) enhances performance; (2) endangers an athlete's health; and (3) violates the spirit of the sport. We herein argue that rapid weight loss clearly meets all three criteria and, therefore, should be banned from the sport. To quote the World Anti-Doping Agency Code, this would "protect the athletes' fundamental right to participate in a doping-free sport and thus promote health, fairness and equality".

Mapping the superficial inferior epigastric system and its connection to the deep system: An MRA analysis.

The superficial inferior epigastric vasculature plays a critical role in free abdominal tissue transfer. However, its anatomic variations are incompletely characterized. An investigation was conducted on the preoperative imaging of patients undergoing free-flap breast reconstruction by a single surgeon between 2008 and 2013. This study included patients who underwent abdominal magnetic resonance angiogram (MRA). A coordinate system was used to draw the main trunk and primary branches from each patient's superficial inferior epigastric system. Each hemiabdomen's branching pattern was categorized as simple, complex, or absent. The number of superficial-to-deep inferior epigastric connections and the presence or absence of a superficial system crossing the midline were recorded. Interrater reliability was assessed for two raters. This analysis included 53 patients (106 hemiabdomens). A total of 80 (75%) hemiabdomens were categorized as having simple and 10 (9%) as complex branching patterns. A total of 16 (15%) hemiabdomens had no identifiable vessels. At least one superficial-to-deep connection was found among 89 hemiabdomens (84%). Superficial systems crossing the midline were found in 14 patients (26%). Our findings support the high degree of anatomic variation in the superficial inferior epigastric system, including a significant number of patients lacking superficial-to-deep connections and bilaterally communicating systems. These variations may be identified on preoperative MRA.

Factors contributing to facial asymmetry in identical twins.

BACKGROUND: This study examines the potential contributions of environmental factors to variations in facial symmetry between identical twins. METHODS: Identical male and female twins were recruited from the Twins Days Festival in 2009 and 2010. Subjects independently completed a comprehensive questionnaire on their medical and personal history, and then posed for digital facial photography from several different angles. Eight facial features from these photographs were measured using Adobe Photoshop, and these facial features were then analyzed against survey responses between twins through multivariate regressions. RESULTS: A total of 147 pairs of identical twins were included. Twins who slept primarily prone had greater nasal midline deviation (p = 0.047) and oral commissure asymmetry (p = 0.027). Tooth extractions were significantly associated with canting of the plane of occlusion (p = 0.043), and use of dentures was associated with nasal midline deviation (p = 0.032) and oral commissure asymmetry (p = 0.007). Smoking was associated with canting of the plane of occlusion (p = 0.049) and upper eyelid ptosis (p = 0.023). Lastly, headaches were also associated with nasal midline deviation (p = 0.024). CONCLUSION: Exogenous factors such as prone sleep position, tooth extractions, dentures, and smoking are significant risk factors for facial asymmetry. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, II.

Genipin as a sporicidal agent for the treatment of cortical bone allografts.

INTRODUCTION: Microbial bioburden in bone allografts can be reduced by gamma radiation; however, the radiation compromises collagen and increases the risk of graft failure. Genipin is an agent that may reduce bioburden by chemical crosslinking without causing mechanical detriment or cytotoxicity. METHODS: To evaluate genipin's ability to penetrate cortical bone while maintaining sporicidal activity, Bacillus subtilis spore strips were isolated between slices of bovine femoral cortical bone and immersed in genipin solutions for up to one week; spore viability was assessed with media-based assays. The mechanical effects of genipin treatment were assessed by performing three-point bending tests on genipin-treated cortical beams. Cytotoxicity studies were conducted by evaluating the adhesion and proliferation of murine MC3T3-E1 (P21) preosteoblasts on cortical bone slices which were treated with genipin and rinsed to different extents. RESULTS: Genipin successfully penetrated cortical bone slices and sterilized B. subtilis populations after 48 hours (p>0.05) and one week (p<0.05). Genipin-treated cortical beams demonstrated dose-dependent increases in yield strain (p=0.02) and resilience (p<0.01), whereas other mechanical properties were not affected by genipin treatment. Seeding cells onto inadequately rinsed genipin-treated bones proved cytotoxic. However, with adequate post-treatment rinsing of the residual genipin, cell adhesion and proliferation was comparable to phosphate-buffered saline-treated controls (no genipin). CONCLUSIONS: Genipin solutions can sterilize bacterial spore populations entrapped within the continuum of bone tissue while preserving mechanical properties of bone and allowing cell adhesion and proliferation. Provided that antimicrobial effects seen with bacterial spores extend broadly to all microbial and viral species, genipin holds strong potential for bone allograft sterilization.

A wireless hybrid chemical sensor for detection of environmental volatile organic compounds.

A hybrid sensor for monitoring volatile organic compounds (VOCs) in air is developed. The device combines two orthogonal sensing principles, selective molecular binding with a microfabricated quartz tuning fork detector and separation of analytes with a column. The tuning fork detector is functionalized with molecular imprinted polymers for selective binding to benzene, toluene, ethylbenzene, and xylenes (BTEX), and the separation column provides further discrimination of the analytes for real world complex sample analysis. The device is wireless, portable, battery-powered, and cell-phone operated, and it allows reliable detection in parts per billion (ppb) by volume-levels of BTEX in the presence of complex interferents. The hybrid device is suitable for occupational, environmental health, and epidemiological applications.

Determinants of breast appearance and aging in identical twins.

BACKGROUND: Appearance, aging, and disorders of the breast are multifactorial. There are intrinsic, patient-specific characteristics, such as breast growth during puberty and propensity for breast cancer, which are primarily inherited. There are also environmental factors, which can be potentially controlled. Monozygotic twins provide an excellent research opportunity to examine the role of extrinsic factors in subjects with identical genetic predispositions. OBJECTIVES: The authors investigate the role and significance of various environmental and acquired factors on breast aesthetics. METHODS: Identical female twins were recruited during the Twins Days Festival in Twinsburg, Ohio, in 2009 and 2010. After consent was obtained, enrolled subjects completed a comprehensive survey on their medical and personal history. Standardized digital photographs were taken by medical photographers. Sixteen aesthetic breast features were subjectively rated by 6 plastic surgery residents blinded to the survey results. These ratings were then analyzed against survey data to determine the significance of different exogenous factors on breast appearance. RESULTS: A total of 161 pairs of identical female twins (n = 322) with a mean (SD) age of 47.6 (14.5) years were recruited. Twins who moisturized their skin daily had significantly fewer rhytids (P = .002). Twins who received hormone replacement therapy after menopause had more attractive breast shape, size, projection, areolar shape, and areolar size (P < .03). However, twins who had a higher body mass index, greater number of pregnancies, and larger cup sizes had significantly less attractive breasts (P < .05). Twins who smoked cigarettes and consumed alcohol also had significantly less attractive breasts (P < .05). Twins who breastfed had less attractive areolar size and shape but better skin quality than their counterparts who never breastfed (P < .03). Finally, there was a significantly higher incidence of breast pain in twins who primarily slept on their sides compared with twins who primarily slept on their backs (P < .008). CONCLUSIONS: This study implicates several environmental factors that significantly affect the aesthetic quality of breasts.

Online sample conditioning for portable breath analyzers.

Various innovative chemical sensors have been developed in recent years to sense dangerous substances in air and trace biomarkers in breath. However, in order to solve real world problems, the sensors must be equipped with efficient sample conditioning that can, e.g., control the humidity, which is discussed much less in the literature. To meet the demand, a miniaturized mouthpiece was developed for personal breath analyzers. A key function of the mouthpiece is to condition the humidity in real breath samples without changing the analyte concentrations and introducing substantial backpressure, which is achieved with optimized packing of desiccant particles. Numerical simulations were carried out to determine the performance of the mouthpiece in terms of various controllable parameters, such as the size, density, and geometry of the packing. Mouthpieces with different configurations were built and tested, and the experimental data validated the simulation findings. A mouthpiece with optimized performance reducing relative humidity from 95% (27,000 ppmV) to 29% (8000 ppmV) whereas retaining 92% nitric oxide (50 ppbV to 46 ppbV) was built and integrated into a hand-held exhaled nitric oxide sensor, and the performance of exhaled nitric oxide measurement was in good agreement with the gold standard chemiluminescence technique. Acetone, carbon dioxide, oxygen, and ammonia samples were also measured after passing through the desiccant mouthpiece using commercial sensors to examine wide applicability of this breath conditioning approach.

A New Sensor for the Assessment of Personal Exposure to Volatile Organic Compounds.

To improve our understanding of indoor and outdoor personal exposures to common environmental toxicants released into the environment, new technologies that can monitor and quantify the toxicants anytime anywhere are needed. This paper presents a wearable sensor to provide such capabilities. The sensor can communicate with a common smart phone and provides accurate measurement of volatile organic compound concentration at a personal level in real time, providing environmental toxicants data every three minutes. The sensor has high specificity and sensitivity to aromatic, alkyl, and chlorinated hydrocarbons with a resolution as low as 4 parts per billion (ppb), with a detection range of 4 ppb to 1000 ppm (parts per million). The sensor's performance was validated using Gas Chromatography and Selected Ion Flow Tube - Mass Spectrometry reference methods in a variety of environments and activities with overall accuracy higher than 81% (r(2) > 0.9). Field tests examined personal exposure in various scenarios including: indoor and outdoor environments, traffic exposure in different cities which vary from 0 to 50 ppmC (part-per-million carbon from hydrocarbons), and pollutants near the 2010 Deepwater Horizon's oil spill. These field tests not only validated the performance but also demonstrated unprecedented high temporal and spatial toxicant information provided by the new technology.

Novel monitor paradigm for real-time exposure assessment.

A wearable monitor that can reliably, accurately, and continuously measure personal exposure levels of various toxicants would not only accelerate the current environmental and occupational health and safety studies, but also enable new studies that are not possible with the current monitoring technology. Developing such a monitor has been a difficult challenge, and requires innovative sensing science and creative engineering. We have developed, built, and tested a wearable monitor for real-time detection of toxic hydrocarbons and acids in the environment. The monitor is low-cost, accurate, and user friendly. In addition, it can communicate wirelessly with a cell phone in which the monitoring results can be processed, displayed, stored, and transmitted to a designated computer. We have validated the functions and performance of the monitor, and carried out field tests with workers involving waste management, fire overhaul, and floor-cleaning activities, as well as with first- and second-hand smokers. The averaged exposure levels are in agreement with those determined by the standard NIOSH methods. The monitor provides accurate and real-time exposure assessment for the workers involving different activities. The real-time and continuous monitoring capability makes it possible to correlate the exposure levels with different activities and changes in the microenvironments. The monitor provides unprecedented real-time information that will help advance occupational safety and environmental health studies. It may also be used to better protect workers from occupational overexposure to toxic molecules.

Ultrasensitive detection of nitrogen oxides over a nanoporous membrane.

A nitrogen oxide (NO(x); x = 1, 2) optical sensor with an extremely low detection limit in the range of fractions of ppbV (0.3 ppbV for 20 s sample injection) is presented. Phenylenediamine derivatives are utilized as molecular probes in the solid state on a nanoporous membrane to produce a miniaturized and low cost sensing platform for use as a wearable personal monitor.

Imaging local electrochemical current via surface plasmon resonance.

We demonstrated an electrochemical microscopy technique based on the detection of variations in local electrochemical current from optical signals arising from surface plasmon resonance. It enables local electrochemical measurements (such as voltammetry and amperometry) with high spatial resolution and sensitivity, because the signal varies with current density rather than current. The imaging technique is noninvasive, scanning-free, and fast, and it constitutes a powerful tool for studying heterogeneous surface reactions and for analyzing trace chemicals.

A hybrid nanosensor for TNT vapor detection.

Real-time detection of trace chemicals, such as explosives, in a complex environment containing various interferents has been a difficult challenge. We describe here a hybrid nanosensor based on the electrochemical reduction of TNT and the interaction of the reduction products with conducting polymer nanojunctions in an ionic liquid. The sensor simultaneously measures the electrochemical current from the reduction of TNT and the conductance change of the polymer nanojunction caused from the reduction product. The hybrid detection mechanism, together with the unique selective preconcentration capability of the ionic liquid, provides a selective, fast, and sensitive detection of TNT. The sensor, in its current form, is capable of detecting parts-per-trillion level TNT in the presence of various interferents within a few minutes.