Two-dimensional (2D) materials have been widely explored in different fields since 2004. More in-depth understanding of their interaction with the environment becomes more and more vital in designing and implementing novel biological devices. Knowing how to use them, how to evaluate their safety in the human body, and how to prepare them cheaply are three critical questions in the investigations of biomaterials. In this thesis, to cover these three questions, I will examine two-dimensional materials in oxygen sensing, cytotoxicity evaluation, friction tunability, substrate-controlled growth and protective layers in arbitrary substrates. First, I will give a general review of the structure, synthesis, and characterizations of two-dimensional materials used in this thesis. Second, I will switch to the project of studying the interplay of MoS2 and oxygen molecules to unveil the strong correlation between p-type doping and photoluminescence enhancement due to the presence of oxygen. Next, to guarantee the safety of 2D biosensor, I will reveal the tunable friction behaviors of MoS2 via the chemical interface of self-assembled molecules which will be helpful in designing clogging-free biosensors. Furthermore, the toxicity of MoS2 flakes and microparticles will be evaluated via MTT without contaminations of samples during synthesis. The results demonstrate the low toxicity of 2H type MoS2 to 6 six different kinds of human cells. The interaction of 2D materials with substrates will be the focus of the last part of this thesis, where I will demonstrate that patterned substrate controls the growth of monolayer MoSe2 and the grown ultrathin h-BN on iron substrate protects the covered substrate against strong acid very well. The extensive coverage in different fields in this thesis provides us with some essential knowledge of these exciting 2D materials in future biomedical applications.