Transient implants that use optical spectroscopy to diagnose local tissue

Bioresorbable Systems for In Vivo, Spectroscopic Measurements of Physiological Status and Neural Activity
Transient implants that use optical spectroscopy to diagnose local tissue

As technology advances, the seamless integration of living organisms with electronic systems is no longer the stuff of fiction but a feasible goal that, if achieved, could create tremendous opportunities in biomedical research and clinical medicine, many of which may even be beyond imagination. Recent breakthroughs have enabled bio-integrated electronics to adopt mechanics compatible with soft tissue and increase biotic–abiotic communications, biocompatibility, and stability. An emerging direction in implantable bioelectronics involves the development of materials and device structures that are entirely resorbable in living biological systems, thereby providing essential diagnostic function in implants that operate for a set timeframe matched to a transient biological process and then bioresorb, to naturally eliminate device load.  Silicon-based pressure sensor and arrays of bioresorbable electrodes for recording electrophysiological signals represent recent examples, where envisioned applications are in temporary biomedical devices designed to monitor the time evolution of recovery process from traumatic injury or of responses to treatment of neurological disorders. 

Figure 1. Bioresorbable photodetector with a bioresorbable fibre optic probe for spectroscopic characterization of biological tissues. a. the photodetector is based on a doped silicon nanomembrane. b. the photodetector is based on a tri-colour Si photodetector.

In this work, we aim to establish a collection of techniques that qualitatively increases the capabilities of such types of bioresorbable systems.  Specifically, we introduce a set of building block components -- multiwavelength photodetectors (Figure 1), multilayer filters (Figure 2) and fiber optic probes (Figure 1) – that can be assembled into platforms capable of full spectroscopic characterization of targeted tissues inside the body.  In vivo demonstrations of multifunctional bioresorbable devices for full spectral and thermal characterization of biotissues and biofluids, continuously and in real time, in the context of neural activity and metabolic processes, illustrate some of the resulting possibilities (Figure 3). 

Figure 2. Bioresorbable optical filter based on multilayer assemblies of films of SiOx and SiNy. a. Cross-sectional SEM image of the multilayer assemblies of films of SiOx and SiNy. b. image of the filter wrapped onto the edge of a glass slide. c. Transmission spectrum of a filter at a 0° incidence angle.

Future developments will focus on system-level integration in order to enable feedback loops and real-time coupling between diagnostics and therapeutics, both of which are useful for fundamental studies of disease pathology and neuroscience. Moreover, they could prove useful for precision medicine and in guiding surgical and recovery processes for certain types of illness and injury.

Figure 3. Monitoring cerebral temperature (a), oxygenation (b) and neural activity (c) in freely moving animal models via spectroscopic measurements using bioresorbable devices.

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Go to the profile of Holly Li
about 3 years ago

this is a great paper