Surfactant excipients preferentially coat surfaces and proteins from unfolding at the interfaces. It can prevent protein aggregation by competing with proteins for adsorption at the air-water interfaces. Other distinct mechanisms of surfactant improve the protein stability by directly interacting with the target protein. Several mechanisms for surfactant stabilization have been proposed in the literature. Nonionic surfactants like polysorbates 80 and their hydrophobic segments can target the hydrophobic region of unfolded protein, thereby decreasing intermolecular interactions and helping protect them from self-association. Studies have also shown that an optimal composition of trehalose and polysorbates 80 can protect the lysozyme and retain more than 92% of the activity compared to the native enzyme. The exposed hydrophobic regions of the unfolded proteins can be protected via polysorbate 80 adsorption. With the presence of surfactant, local interaction and surface tension can be altered to modulate the adsorption loss and enable protein disaggregation and refolding by coating the interface and involved in proteinsurfactant associations as stated by Furthermore, Surfactant can also increase the free energy of protein and potential serve as a chemical chaperone which provides sterically hindering in intermolecular interaction leading to aggregation and supporting folded protein. Warne et al. reviewed recent high-concentration biologics solutions and lyophilized formulations and found 16 of the 21 antibody formulations contain either polysorbate-20 or polysorbate-80. Learning from the commercial examples, the inclusion of surfactant in the protein formulation is highly recommended and the amount of surfactant to include in the products to protect from interfacial stress is the critical parameter to optimize. Concentration selection of polysorbate 80 in protein formulations can mitigate the stability issue on protein thermal and photostability demonstrated by Agarkhed et al. Besides the benefits of using surfactants to provide additional stabilization for protein stabilization, there have been concerns regarding the residual amounts of peroxide which might induce oxidation risk which can lead to the loss of protein potency and stability during storage. 5.3 Physicochemical attributes in frozen solution: Buffer, Sugar, and Protein Phase and Dynamics