**4.3. Medical and diagnostics applications**

Both chip-based and independent porous silicon structures have been utilized for medical and diagnostics applications. Biosensors have been realized to detect proteins, enzymes, and antibodies. For instance, porous silicon has been used to measure the prostate-specific antigen (PSA) in order to diagnose prostate cancer. Brachytherapy, insertion of radioactive implants directly into the target tissue, has also used this material to treat cancer. In this technique a medical radioisotope is placed in a porous silicon capsule and injected into the tissue requiring destruction. Meanwhile, biodegradable porous silicon is under preclinical test for drug delivery. The material's tunable pore size and modifiable surface chemistry make tunable drug load and release possible and therefore put porous silicon forward as a potential candidate for this carrier technology. Finally, porous silicon can be considered for tissue engineering due to its desirable properties. In this regenerative medicine, a temporary biodegradable scaffold is implanted in the body so that the tissue could heal itself around it. Accordingly, the scaffold should be made from a biocompatible material that could be easily synthesized, formed and controllably dissolved.

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