Posterior scleritis after biweekly aflibercept intravitreal injections.

Purpose: To describe a case of posterior scleritis following anti-vascular endothelial growth factor (VEGF) injection. Observations: A 51-year-old male receiving biweekly anti-VEGF injections for a central retinal vein occlusion complicated with cystoid macular edema presented with new-onset severe pain, photophobia, and tearing. Ophthalmological examination revealed choroidal folds and B-scan ultrasound confirmed significant thickening of the sclera, leading to a diagnosis of posterior scleritis. This resolved under topical and systemic corticosteroids. Conclusions and importance: Intravitreal anti-VEGF injections could be associated with non-infectious posterior scleritis. Clinicians should be particularly aware of this possibility in patients receiving frequent injections.

Real-time monitoring of bead-based DNA hybridization in a microfluidic system: study of amplicon hybridization behavior on solid supports.

DNA hybridization phenomena occurring on solid supports are not understood as clearly as aqueous phase hybridizations and mathematical models cannot predict some empirically obtained results. Ongoing research has identified important parameters but remains incomplete to accurately account for all interactions. It has previously been shown that the length of the overhanging (dangling) end of the target DNA strand following hybridization to the capture probe is correlated to interactions with the complementary strand in solution which can result in unbinding of the target and its release from the surface. We have developed an instrument for real-time monitoring of DNA hybridization on spherical particles functionalized with oligonucleotide capture probes and arranged in the form of a tightly packed monolayer bead bed inside a microfluidic cartridge. The instrument is equipped with a pneumatic module to mediate displacement of fluid on the cartridge. We compared this system to both conventional (passive) and centrifugally-driven (active) microfluidic microarray hybridization on glass slides to establish performance levels for the detection of single nucleotide polymorphisms. The system was also used to study the effect of the dangling end's length in real-time when the immobilized target DNA is exposed to the complementary strand in solution. Our findings indicate that increasing the length of the dangling end leads to desorption of target amplicons from bead-bound capture probes at a rate approaching that of the initial hybridization process. Finally, bead bed hybridization was performed with Streptococcus agalactiae cfb gene amplicons obtained from randomized clinical samples, which allowed for identification of group B streptococci within 5-15 min. The methodology presented here is useful for investigating competitive hybridization mechanisms on solid supports and to rapidly validate the suitability of microarray capture probes.

Reagentless ultrasensitive specific DNA array detection based on responsive polymeric biochips.

Self-assembled molecular structures immobilized on solid substrates and composed of fluorophore-tagged oligonucleotide probes and an optical polymeric transducer were investigated for the trace level detection of DNA target molecules. Rapid and efficient energy transfer between the polymeric transducer and fluorophores within the molecular aggregates leads to a massive intrinsic amplification of the fluorescence signal and to the label-free detection of as little as 300 DNA molecules, with the specificity required for the detection of single-nucleotide mismatches. This capacity for attomolar detection levels while the sensing structures are attached onto solid supports could lead to the development of biochip platforms for fast and simple PCR-free multitarget DNA detection.

PCR-free DNA detection using a magnetic bead-supported polymeric transducer and microelectromagnetic traps.

A fluorescent polymeric hybridization transducer supported on magnetic microbeads was investigated for the rapid, ultrasensitive, and sequence-specific detection of DNA. We show that the polymer derivative can be used to detect target DNA directly on magnetic particles by preparing "target-ready" microbeads grafted with the polymer and suitable DNA probes. A detection limit of approximately 200 target copies in a probed volume of 150 muL (1.4 copies/muL) was obtained for a DNA sequence specific to Candida albicans This detection scheme does not require the release of the hybridized target DNA prior to its detection or the labeling or amplification of the nucleic acids. Furthermore, we show that the fluorescence from these biosensing magnetic beads can be read while magnetically confined in a small volume by a microelectromagnetic trap, which offers the possibility of performing both the preconcentration and detection steps simultaneously on the same support. The combination of the fluorescent polymer biosensor with magnetic particle-assisted DNA preconcentration extends the application of this ultrasensitive biosensor to biological samples with complex matrixes and to integrated lab-on-a-chip platforms, where it could be used for fast multitarget DNA detection in point-of-care diagnostics and field analysis.

Use of sol-gels as solid matrixes for trace analysis by UV laser ablation and laser-enhanced ionization detection.

Zirconium and silicon sol-gels were investigated as solid materials for trace elemental analysis of pelletized solid samples by laser ablation and laser-enhanced ionization. The highly homogeneous dispersion of an internal standard spiked in the solid material obtained with the sol-gel formation process leads to a significant improvement in signal repeatability and to an increase in the precision of measurements through better correction of variations in the laser ablation rate. Signal repeatability values of 5-8% RSD were obtained for Pb in NIST 1632c Bituminous Coal sample pellets prepared using both sol-gels, as compared to 9-21% for graphite-based sample pellets. Furthermore, the zirconium sol-gel was shown to offer better resilience to signal bias due to preferential ablation and a more accurate correction of ablation rate using the internal standardization method.

Multielemental laser-enhanced ionization spectrometry for the determination of lead at the trace level in pelletized coal using laser ablation and internal standard signal normalization.

Laser ablation laser-enhanced ionization (LA-LEI) was used for the simultaneous measurement of lead and indium in pelletized graphite and coal samples. UV Laser ablation of the solid samples was performed in an ablation cell and the ablated material was carried by a flow of gas to a miniature LEI flame where lead was detected. The influence of parameters such as binder content of the solid pellets and dispersion of the analytes spiked in the sample material, as well as the number of ablation pulses per crater on signal repeatability and on the size and shape of ejected particles was examined. Measurement repeatability values of 2 to 5% of relative standard deviation were obtained using indium as an internal standard to correct for variations in the ablation rate. A limit of detection of 120 nanograms per gram was calculated for the determination of Pb in high-purity graphite. The Pb concentration in the NIST 1632c Bituminous Coal certified reference material was determined to within 1% of its certified value, using graphite as the matrix-matching material and In as the internal standard in pelletized solid samples.

Trace level determination of lead in solid samples by UV laser ablation and laser-enhanced ionization detection.

Laser-enhanced ionization was investigated as a detection technique for trace elemental analysis of solid samples by laser ablation. Laser ablation of aluminum samples was performed in an ablation cell, and the ablated material was carried by a flow of gas to a miniature LEI flame where Pb was detected. This decoupling of ablation cell and detector allowed the independent optimization of vaporization and detection processes. We have investigated the different excitation schemes for Pb and uncovered five new LEI-active transitions in the visible range. We have demonstrated that the use of an argon-oxygen/acetylene flame sheathed with argon resulted in the elimination of background interference from the two-photon ionization of nitric oxide. We have shown that the use of helium as a carrier gas results in a higher ablation yield and lower pulse-to-pulse variations in LEI signal and in better analytical figures of merit. We have characterized the performance of the technique in terms of detection limits and dynamic range, and we have obtained a detection limit of 60 ng/g for the determination of Pb in high purity aluminum.