## 4 Discussion
### In-Vitro Biocompatibility Analysis  
Along with an excellent degradation rate and better strength, an implant material should also possess a high level of biocompatibility. The non-toxic behavior of a biomaterial is an essential component to be considered for a standard material for bone therapeutic applications. However, the biodegradation of a material can cause a certain level of toxic effects in the body and inflammatory effects due to bactericidal actions. Maintaining a trade-off between strength, resistance against bacterial attack, and cytotoxicity is an essential factor where many studies seem to fail. The porous Mg-HA composite developed in the present study showed excellent biocompatibility and effective mechanical and surface properties. The addition of aloe vera as an anti-inflammatory and antibiotic solution fashioned the current composite into an antibacterial and cytocompatible biomaterial. Aloe vera has several antiseptic properties, holding components such as salicylic acid, urea nitrogen, sulfur, phenols, and cinnamomic acid. These components show inhibitory effects against fungi, bacteria, and viruses. Moreover, they inhibit the cyclooxygenasegenase pathway and resist arachidonic acid from producing prostaglandin E2 [79]. This property helps develop anti-inflammatory effects for bone therapeutic applications by reducing the inflammatory issues triggered due to implant grafting. The bacterial activity was analyzed against the different concentrations of aloe vera solution initially, i.e., 50% to 100%, to assess the minimum concentration of aloe vera solution required to resist bactericidal activity. It was found that a minimum of 50%, i.e., 50 mg/mL of aloe vera solution, is required to resist bacterial growth. However, these results were effective only against Gram-positive (_B. subtilis_) bacteria but not Gram-negative (_E. coli_) bacteria. Although the solution showed only contact inhibition against _E. coli_, the PLA coating had a higher inhibitory effect. In the case of _B. subtilis_, the solution and when infused in the substrate along with the PLA coated sample, showed similar effects. Various authors have highlighted a similar behavior of plant extracts against bacterial strains in their studies. These studies showed a higher inhibitory effect against Gram-positive bacteria as compared to Gram-negative [80; 81]. This could be due to several factors, including the presence of many components in the aloe vera plant, such as phenols, polysaccharides, etc., and a different secondary metabolite. Moreover, aloe vera consists of certain other components named hydroxylated phenol, also known as pyrocatechol, which is known to have a highly toxic effect against microorganisms. These components are highly effective against Gram-positive bacteria. The Gram-negative bacteria's outer membrane consists of lipopolysaccharidesacharides responsible for creating a barrier against these components. Moreover, the periplasmic space of enzymes in the Gram-negative bacteria tends to break down molecules entering from outside the bacteria wall, reducing their antibacterial effects [82,83]. Hemocompatibility is a crucial factor that validates the implant's toxicity when encountering blood cells. In the current study, the developed material showed impressive hemolytic behavior. To be considered non-hemolytic, a material should possess a percent  
Figure 11: Pictorial representation showing (**a**) Mg–HA based substrate undergoing corrosion mechanism after coating with PLA and (**b**) effect of aloe vera on the bacterial cells and corresponding bone regeneration cells proliferation. age hemolysis rate below 5%; above that, it is considered unsuitable for further biomedical applications [84]. The aloe vera addition to the porous Mg-HA substrate showed an excellent hemolysis rate relative to other samples. Nonetheless, when coated with PLA, this percentage increased by 22% but was entirely below the 5% barrier.