Cell secretion dynamics plays a central role in physiological and disease processes. Due to its various temporal profiles, it is essential to implement a precise detection scheme for continuous monitoring of secretion in real time. The current fluorescent and colorimetric approaches hinder such applications due to their multiple time-consuming steps, molecular labeling, and especially the 'snapshot' endpoint readouts. Here, we develop a nanoplasmonic biosensor for real-time monitoring of live cell cytokine secretion in a label-free configuration. Our nanoplasmonic biosensor is composed of gold nanohole arrays supporting extraordinary optical transmission (EOT), which enables sensitive and high-throughput analysis of biomolecules. The nanobiosensor is integrated with an adjustable microfluidic cell module for the analysis of live cells under well-controlled culture conditions. We achieved an outstanding sensitivity for the detection of vascular endothelial growth factor (VEGF) directly in complex cell media. Significantly, the secretion dynamics from live cancer cells were monitored and quantified for 10 hours while preserving good cell viability. This novel approach of probing cytokine secretion activity is compatible with conventional inverted microscopes found in a common biology laboratory. With its simple optical set-up and label-free detection configuration, we anticipate our nanoplasmonic biosensor to be a powerful tool as a lab-on-chip device to analyze cellular activities for fundamental cell research and biotechnologies.

HIV has become one of the most devastating pathogens in human history. Despite fast progress in HIV-related basic research, antiretroviral therapy (ART) remains the most effective method to save AIDS patients' lives. Unfortunately, ART cannot be universally accessed, especially in developing countries, due to the lack of effective treatment monitoring diagnostics. Here, we present an inexpensive, rapid and portable micro-a-fluidic platform, which can streamline the process of an enzyme-linked immunosorbent assay (ELISA) in a fully automated manner for CD4 cell count. The micro-a-fluidic CD4 cell count is achieved by eliminating operational fluid flow via “moving the substrate”, as opposed to “flowing liquid” in traditional ELISA or microfluidic methods. This is the first demonstration of capturing and detecting cells from unprocessed whole blood using the enzyme-linked immunosorbent assay (ELISA) in a microfluidic channel. Combined with cell phone imaging, the presented micro-a-fluidic ELISA platform holds great promise for offering rapid CD4 cell count to scale up much needed ART in resource-constrained settings. The developed system can be extended to multiple areas for ELISA-related assays.

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We demonstrate monolithically integrated n-GaAs/p-Si depletion-type optical phase shifters fabricated on a 300 mm wafer-scale Si photonics platform. We measured the phase shifter performance using Mach–Zehnder modulators with the GaAs/Si optical phase shifters in both arms. A modulation efficiency of V π L as low as 0.3 V·cm has been achieved, which is much lower compared to a carrier-depletion type Si optical phase shifter with pn junction. While propagation loss is relatively high at ∼ 6.5    dB / mm , the modulator length can be reduced by the factor of ∼ 4.2 for the same optical modulation amplitude of a Si reference Mach–Zehnder modulator, owing to the high modulation efficiency of the shifters.

We report p-i-n InGaAs/GaAs multi-quantum well nano-ridge waveguide photodetectors monolithically integrated on a 300-mm Si wafer. The devices exhibit low dark currents of 0.3 pA (1.36x10 -7 A/cm 2 ) at -1V bias and internal responsivities of 0.65A/W at 1020nm wavelength.

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