Why should test our biomaterial and how to test?
Firstly, we have to introduce a concept called biocompatibility: before introducing a new material to contact with cells (implantation), it is important that to choose the suitable, non-toxic/ non-harmful and no-immune reactions one, as a sum saying, which must be biocompatible, in order to ensure our biomaterials will finish the honour risks belong to them and will not cause any adverse influences for patients, therefore, we can easily understand why should we test their prior before.
By Lotfi et al., (2013) in 1987, Williams D.F suggested the following definition «biocompatibility is the ability of a material to be used with an appropriate and suitable reaction of the host for a specific application».
In our example, magnesium is so suitable significantly because its light weight, great mechanical properties and compatibility with human physiology. (Staiger et al., 2006)
Biocompatibility testing have both in vivo and in vitro test.
In vitro test, mainly for cytotoxicity because essentially the biomaterials are reacting with cells.
According to Kamiloglu et al. (2020), cell viability assays be broadly classified as:
1. Dye exclusion assays by trypan blue, eosin, congo red and erythrosine B.
2. Colorimetric assays, including MTT assay, MTS assay, XTT assay, WST-1 assay, WST-8 assay, LDH assay, SRB assay, NRU assay and CVS assay.
3. Fluorometric assays mainly by resazurin (alamar blue) assay.
4. Luminometric assays by real-time viability assay and ATP assay.
5. Flow cytometric assays have membrane permeability and asymmetry assays. (BUT just pass by is fine)
MTT assay and LDH assay are be widely used. MTT assay is an easy way to determine cell metabolism and survival colorimetry. The principle is that metabolically active cells convert MTT to purple methylene dye product, and quantitatively measured at 570nm by spectrophotometer but must be eluted by isopropanol before. The intensity is proportional to the account of viable cells.
Lactate dehydrogenase (LDH) assay is a rapid sensitive method for detect toxicity. LDH is a stable cytoplasmic enzyme and will be oxidizes reduced to nicotinamide adenine dinucleotide (NADH), generating to NAD+, finally get pyruvate (Figure 9). In the process NADH makes series of item into a water-soluble red formazan dye, and the amount of formazan is determined considering the absorbance values measured at 490 nm, which represents the total LDH activity in the culture and it is directly proportional to the number of damaged cells (Kumar, Nagarajan, & Uchil, 2018).
The purpose of implantation experiments (in vivo) is to explore the local effects of biomaterials at the implantation site and to evaluate the pathological effects of biomaterials in vivo, anatomical, pathological, physiological and biochemical features also be considered, which is very important. Mice, rats, guinea pigs and rabbits are commonly used animals for short-term normally within 12 weeks, testing of subcutaneous tissues, muscles and bones long-term tests, usually select like dogs, sheep, goats, pigs and so on. Generally saying, selecting sheep for testing substitute heart, and for ventricular assist devices and total artificial hearts, calves are usually choice. (Shajkumar, 2015)