Implantable microdevices often have static components rather than moving parts, and exhibit limited biocompatibility. This paper demonstrates a fast manufacturing method which can produce features in biocompatible materials down to tens of microns in scale, with intricate and composite patterns in each layer. By exploiting unique mechanical properties of hydrogels, we developed a “locking mechanism” for precise actuation and movement of freely moving parts, which can provide functions such as valves, manifolds, rotors, pumps, and delivery of payloads. Hydrogel components could be tuned within a wide range of mechanical and diffusive properties, and can be controlled after implantation without a sustained power supply. In a mouse model of osteosarcoma, triggering of release of doxorubicin from the device over ten days showed high treatment efficacy and low toxicity, at one-tenth of a standard systemic chemotherapy dose. Overall, this platform, called “iMEMS”, enables development of biocompatible implantable microdevices with a wide range of intricate moving components that can be wirelessly controlled on demand, in a manner that solves issues of device powering and biocompatibility.
This letter demonstrates a microfluidic platform for enumerating CD4+ T-lymphocytes from whole blood using chemiluminescence as a detection method. We microfabricated traps in a chamber and coated them with anti-CD4 antibody to isolate CD4+ T-cells. Based on cell surface-bound CD3 antibodies conjugated with horseradish peroxidase, incubation with chemiluminescent substrate produced a current in the photodetector that was proportional to the number of captured CD4+ T-cells. Analyzing 3 microL of whole blood, the platform exhibited high cell-capture efficiency and produced cell counts with high correlation to results obtained from flow cytometry. Compared to other lab-on-a-chip methods for CD4 counting, this method uses an instrument that requires no external light source and no image processing to produce a digitally displayed result only seconds after running the test.
BACKGROUND:Collection of epidemiological data and care of patients are hampered by lack of access to laboratory diagnostic equipment and patients' health records in resource-limited settings. We engineered a low-cost mobile device that combines cell-phone and satellite communication technologies with fluid miniaturization techniques for performing all essential ELISA functions.
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