Electrospun nanofibers have been widely used in various application due to its high surface-to-volume ratio and high porosity and the interconnectivity of electrospun supports. Especially, Polystyrene-based nanofibers have been developed as a nanostructured support for immobilization of biomolecules because of clear moderately strong polymer, biological inertness, and good dimensional stability. In this thesis, I have studied two kinds of researches using Polystyrene-based nanofibers. One is used for enzyme immobilization in forms of enzyme coatings. Enzyme coatings (EC), one of nanobiocatalysis approach, prepared via covalent attachment of seed enzyme molecules and follow-up enzyme crosslinking, resulted in highly stable nanobiocatalytic systems. Trypsin was immobilized in forms of enzyme coatings on electrospun nanofibers. Trypsin-coated nanofibers showed higher stability than the covalently-attached TR as well as free trypsin, at high temperatures, in the presence of co-solvents, and under various pH conditions. Highly-stable trypsin coating was successfully employed for the repeated protein digestions at an elevated temperature. The concentration of maleic anhydride group of Polystyrene-based nanofibers could be adjusted by the amount of poly(styrene-co-maleic anhydride) (PSMA) in the mixture of polymer solution for electrospinning. Trypsin coatings on polymer nanofibers at various blending ratio of polystyrene and poly(styrene-co-maleic anhydride) were effective in preventing the leaching, denaturation, and autolysis of trypsin, which stabilized the activity of trypsin coatings irrespective of the added PSMA amounts. Polystyrene-based nanofibers could be dispersed in aqueous solutions via simple alcohol treatment. In a comparative study with the trypsin coatings on as-spun and dispersed nanofibers, it has been observed that a simple step of alcohol dispersion improved not only the enzyme loading but also the performance of protein digestion. By applying the alcohol dispersion of polymer nanofibers, the bypass of samples was reduced by filling up the column with well-dispersed nanofibers, and In-column digestion of enolase was successfully performed in less than twenty minutes. The other is used for application of cell capture. Ethanol treatment of Polystyrene-based nanofibers, employed for the purpose of sterilization, significantly increased their inter-fiber space for both antibody conjugation and subsequent cell separation. For the selective isolation of CD4+ T cells from heterogeneous mixtures of mouse lymph nodes, capture efficiencies of up to 100% could be achieved while maintaining cellular integrity and viability.These platform based electrospun polystyrene nanofibers will provide new opportunities for both conventional and newly emerging areas of enzyme applications and apply in in vivo targeted cell expansion and sustained cell delivery systems as an innovative protocol of immune cell therapies.