Mechanical manipulation of bone and cartilage cells with 'optical tweezers'

The single beam optical gradient trap (optical tweezers) uses a single beam of laser light to non-invasively manipulate microscopic particles. Optical tweezers exerting a force of approximately 7 pN were applied to single bone and cartilage derived cells in culture and changes in intracellular calcium levels were observed using Fluo-3 labelling. Human derived osteoblasts responded to optical tweezers with an immediate increase in [Ca2+](i) that was inhibited by the addition of a calcium channel blocker nifedipine, Force applied to different regions of cells resulted in a variable response. [Ca2+](i) elevation in response to load was lower in rat femur derived osteoblasts, and not apparent in primary chondrocytes and the osteocytic cell line (MLO Y4). (C) 1999 Federation of European Biochemical Societies.