Optical tweezers (OT) are becoming a popular tool in medicine and biology for the manipulation and the analysis of cells and microorganisms. In recent years an impelling demand has arisen for the development of miniaturized trapping devices that can be easily combined with microfluidic circuits where to study complex phenomena on a micro- or sub-micro scale. We demonstrated novel miniaturized optical tweezers based on optical fibers for manipulation of single cells. The realization is based on the fabrication of micro-prisms on the output facet of a single fiber-bundle by TPL. Such devices represent a considerably improved version, both in terms of easiness of fabrication and of trapping performance, of an earlier realization based on the focused-ion-beam microstructuration of the fiber end-faces. By using these fiber-optic tweezers (FOT) we demonstrate contactless 3D optical trapping and manipulation of both polystyrene beads and human cancer cells. Moreover we demonstrated successful integration of our FOT with a microfluidic chip.