All-fiber surface-enhanced Raman scattering detection system combining an integrated microfluidic chip and micro-lensed fiber.

It is a challenge to perform simple and rapid detection of substances due to their complex structure. Biochemical molecules play a vital role in human health and environmental testing. Surface-enhanced Raman scattering (SERS) detection has the characteristics of strong specificity and real-time performance. At present, most SERS systems are expensive and not portable. Here, we demonstrate a SERS detection system with all-fiber connection, combined with a microfluidic chip and micro-lenses. Compared with the conventional SERS system that uses the spatial optical path, the devices in our system are connected by optical fibers, making the system more stable and operable. Besides, the microfluidic chips are introduced to further improve the system integration and stability. Owing to the micro-lensed fiber probe, the detected Raman signal intensity is increased by 2-3 times. We anticipate that the presented work will lead toward a rapid and portable SERS system and corresponding detection system. It also lays the foundation for real-time recognition in various complex environments in the design of a future optical fiber system.

Multivision demodulation of the FBG based on a thermal-induced chirp and a shallow neural network.

We present a high-precision, low-cost demodulation method for the fiber Bragg grating (FBG) using a thermal-induced chirp and a shallow neural network. The thermal-induced chirp of a semiconductor laser generates the different wavelength components in a single pulse, which will form an exponential function echo signal after being reflected by the FBG. By learning the shape of the reflected light, the back-propagation neural network can simultaneously demodulate the sensing temperature and laser power. The whole detection system has only a few basic detection devices, which makes it low cost. The experimental results show that the multivision demodulation (MVD) method can reach a high demodulation precision of 0.35°C. We believe these results indicate the MVD method is an outstanding scheme in the field of FBG interrogation.

Hybrid plasmonic grating slot waveguide with high field enhancement for an on-chip surface-enhanced Raman scattering sensor.

We design and theoretically investigate a surface-enhanced Raman scattering (SERS) sensor based on the hybrid plasmonic grating slot waveguide. The sensor is formed by combining a dielectric deep slot waveguide and a metallic grating slot waveguide. The proposed sensor exhibits a high field enhancement with a maximum enhancement factor of 7580.9 at the wavelength of 785 nm, revealing that the electric field in such hybrid plasmonic grating slot waveguide can be extremely strengthened. To better characterize the performance of the sensor in the SERS application, the total normalized volumetric enhancement factor (TNVEF) is proposed, which is determined by both the |E|4-approximation-based volumetric field enhancement and Raman scattered light collection efficiency. The TNVEF is utilized to characterize the influences of the structural parameters on the sensor and further optimize the sensing structure. Such on-chip SERS sensor can be integrated with a micro-laser and a micro-multiplexer on a photonic platform to realize an all-integrated on-chip SERS detection system.

Strain-specific differences in two large Mycobacterium tuberculosis genotype clusters in isolates collected from homeless patients in New York City from 2001 to 2004.

We studied two large Mycobacterium tuberculosis genotype clusters associated with recent outbreaks in homeless persons to determine factors associated with these tuberculosis (TB) strains. Isolates from all culture-positive TB cases diagnosed from 1 January 2001 to 31 December 2004 were genotyped. Patients whose isolates had identical restriction fragment length polymorphism patterns and spoligotypes were considered clustered. Health department records were reviewed and reinterviews attempted for clustered cases. Patients with the Cs30 and BEs75 strains were compared to other genotypically clustered cases and to each other. The two largest genotype clusters among homeless persons were the Cs30 strain (n = 105) and the BEs75 strain (n = 47). Fifty-one (49%) patients with the Cs30 strain and 28 (60%) with the BEs75 strain were homeless. Compared to patients with the BEs75 strain, patients with the Cs30 strain were less likely to be respiratory acid-fast bacillus smear positive (51% versus 72%). Furthermore, patients with the BEs75 strain were more likely to be HIV infected (74% versus 42%), which suggests that most patients with this strain advanced to disease after recent infection. Cases in clusters of strains that have been circulating in the community over a long time period, such as the Cs30 strain, require additional investigation to determine whether clustering is a result of recent transmission or reactivation of remote infection.

Which patients' factors predict the rate of growth of Mycobacterium tuberculosis clusters in an urban community?

Factors influencing tuberculosis cluster growth are poorly understood. The authors examined clusters of two or more culture-confirmed Mycobacterium tuberculosis cases between January 1, 2001, and December 31, 2003, that had insertion sequence 6110 (IS6110) restriction fragment length polymorphism and spoligotype patterns identical to those of another study case. Genotypes first seen in New York, New York, before or during 1993 were considered historical; recent strains were those first seen after 1993. The authors examined the effect of the combined characteristics of infectiousness of the first two cases in a cluster on the rate of cluster growth. Genotyping was performed for 2,408 (91.8%) of the 2,623 tuberculosis cases diagnosed; 873 cases were in 212 clusters. Thirty-one clusters had historical strains, 153 were recent, and 28 were of unknown period. Patients' infectiousness was not associated with the rate of cluster growth among historical strain clusters. Among recent strain clusters, infectiousness of both of the initial cases was associated with a higher rate of cluster growth compared with clusters in which neither initial case was infectious, upon adjustment for male sex (rate ratio = 2.62, 95% confidence interval: 1.19, 5.78). The rate of genotype cluster growth should be monitored regardless of how long the strain has been present in the community. However, infectiousness in the first two cases may be useful to prioritize genotype cluster investigations.

Universal genotyping in tuberculosis control program, New York City, 2001-2003.

In 2001, New York City implemented genotyping to its tuberculosis (TB) control activities by using IS6110 restriction fragment length polymorphism (RFLP) and spoligotyping to type isolates from culture-positive TB patients. Results are used to identify previously unknown links among genotypically clustered patients, unidentified sites of transmission, and potential false-positive cultures. From 2001 to 2003, spoligotype and IS6110-based RFLP results were obtained for 90.7% of eligible and 93.7% of submitted isolates. Fifty-nine (2.4%) of 2,437 patient isolates had false-positive culture results, and 205 genotype clusters were identified, with 2-81 cases per cluster. Cluster investigations yielded 57 additional links and 17 additional sites of transmission. Four additional TB cases were identified as a result of case finding initiated through cluster investigations. Length of unnecessary treatment decreased among patients with false-positive cultures.

Recombinant gamma interferon stimulates signal transduction and gene expression in alveolar macrophages in vitro and in tuberculosis patients.

Tuberculosis is the seventh leading cause of morbidity and mortality in the world, with eight million cases per year. Animal and human studies demonstrate an enrichment of CD4 cells at sites of disease, with a more favorable clinical course when there is a Th1 response with the presence of gamma interferon (IFN-gamma). We previously treated patients who had multidrug-resistant tuberculosis with recombinant IFN-gamma (rIFN-gamma) in aerosol form and were able to convert smear-positive cases to smear negative with 12 treatments over 1 month. We hypothesized that rIFN-gamma would induce signal transducer and activator of transcription (STAT) and interferon regulatory factor (IRF) binding activity in alveolar macrophages (AM). AM treated in vitro showed clear upregulation of STAT-1 and IRF-1 by rIFN-gamma. STAT-1 was not activated and IRF-1 was only weakly induced after 1 day of infection by Mycobacterium tuberculosis TN913. In bronchoalveolar lavage (BAL) cells obtained from 10 of 10 tuberculosis patients 10 +/- 2 days post-antituberculosis treatment, there was no detectable STAT-1 or IRF-1 DNA-binding activity. After 4 weeks of treatment with rIFN-gamma aerosol in addition to the antituberculosis drugs, 10 of 10 patients had increased STAT-1, IRF-1, and/or IRF-9 DNA-binding activity in BAL cells from lung segments shown radiographically to be involved and in those shown to be uninvolved. Symptoms and chest radiographs improved, and amounts of macrophage inflammatory cytokines and human immunodeficiency virus type 1 (HIV-1) viral loads (in five of five HIV-1-coinfected patients) declined in the second BAL specimens. rIFN-gamma aerosol induces signal transduction and gene expression in BAL cells and should be evaluated for efficacy in a randomized, controlled clinical trial.