A device for the spatio-regional delivery of a photocurable drug formulation

We devised a new transtissue drug-delivery system, based on a multiple-needle-arrayed injector that has 36 long and short needles on the needle head, to administer the drug into local points of the target tissue at a well-controlled depth and pitch. A preliminary in vitro study, focusing the time-dependent depth profiling of protein injected in agarose gel as a model tissue using confocal laser scanning microscope, was conducted to evaluate the performance of the multiple-needle-arrayed injector coupled with photoreactive gelatin (styrenated gelatin: St-gelatin) as the sustained-release vehicle. Rhodamine-conjugated albumin, which was mixed with the St-gelatin buffer solution, was the model drug of the in vitro study, and the mixture was injected into agarose gel using the multiple-needle-arrayed injector by single injection, followed by visible-light irradiation to photocure the gelatin solution. Time-dependent distribution from the injected material into the surrounding agarose gel was observed using a confocal laser scanning microscope up to seven days. Injection of the drug material and concomitant withdrawal of the syringe (termed multirod method) enabled the long- and short-rod-like injections into the agarose gel at the same locations of the injected sites. The model drug gradually diffused throughout the agarose gel. In an in vivo study, the comparison of the efficacy of the angiogenic protein (bFGF: 10μg for each) with placebo was performed using the non-ischemic hind limb model of rabbits. Four weeks after injection, a significant increase in the number of angiogenic capillaries was observed in the mixed St-gelatin/bFGF group compared with that of placebo. The multiple-needle-arrayed injector coupled with a sustained-release vehicle may be an effective drug delivery system for realizing the spatio-regional distribution of angiogenic protein.