Monitoring systemic changes in body fluid
The interactions between biodegradable metals with the local tissue induce biological responses, e.g., local cell proliferation and systemic cellular migration to a local implantation site, as illustrated in Fig. 2.3. Cellular differentiation and proliferation was considered by specific biochemical substrates that utilized the specific cells for each body event during cellular communication. The form of biochemical substrates that are used for cell communication include growth factors, hormones, and other specific substrates that are released in the extracellular fluid [96,97]. These substrates could be analyzed and also can be used as biomarkers in order to monitor the progression of degradation.
Body fluids are a potential source of many biomarkers that can be collected from living animals in many ways, both noninvasive (i.e., sweat, saliva, milk, and urine) and invasive (i.e., blood, cerebrospinal fluid). Some biomarkers are currently assessed by using immunoassay-based analysis such as enzyme immunoassay, enzyme-linked immunosorbent assay, and radio immunoassay. Implantation of different types of biomaterials shows a different trend of growth factors that are released from the microenvironment. For example, osteoblast cells release transforming growth factor-p1 (TGF-P1) in higher concentration after in contact with acrylic bone cement compared to bioinert metallic-based biomaterials such as titanium and cobalt chromium [98,99]. This kind of biomarker has the potential to be utilized as a marker for monitoring the degradation of biodegradable metal implants with specific molecular biological responses after insertion in the body.
Off-clinic point-of-care implant monitoring
Point-of-care diagnostics using the microfluidic system have been introduced in order to speed up the diagnosis process on the site of assessment . A microfluidic technology is considered as a simple, compact (integrated system), rapid, specific, sensitive, and low-cost analytical device with the microvolume of samples provided from invasive or noninvasive procedures. In a point-of-care system, patients can monitor their health status using a simple diagnostic tool, such as a portable blood glucose monitoring device. The patients can directly collect their blood samples using a lancet, and the device will measure the glucose level. The same colorimetric-based principle may also be applicable for monitoring metal ions released from a biodegradable metal implant.