ABSTRACT
@#【Objective】To form a new PTMAc- PEG- PTMAc triblock（PPP）copolymerhydrogel and to evaluate its sustained released performance and antiproliferative effects as an ocular drug carrier of Pirfenidone（PFD）【Methods】One type triblockcopolymers PPP hydrogel was chosen. The morphology of the material was evaluated by scanning electron microscopy（SEM）. The swelling properties of the PPP hydrogel was analyzed in PBS solution（37 ℃ ，pH 7.4）. The in vitro drug release of the pirfenidone loaded hydrogels were evaluated with non-dialysis method and the curves of drug release were drawed. We evaluated the adhesion，survival of human Tenon′s capsule fibroblasts（HTF）around hydrogels. The cell cytotoxicity of hydrogels and antiproliferative effects were evaluated through CCK-8 assay.【Results】The hydrogel has stable gelation conditions. The swelling rate decreased by increasing hydrogel concentration.The SEM images indicated the fibrous and porous structure. We also observed that the encapsulated pirfenidone were sustained released from hydrogels with an initial burst release at early stage（within 4 d）and then the release rate were declined for all hydrogels during the following 14 d. The PPP hydrogel can inhibit cell adhesion. The cell viability in hydrogels at four time point（24，48，72 and 96 h）were 85.7% ，93.0% ，82.0% ，81.6%. The inhibition rate of drug loaded hydrogel with two drug concentration（1 mg/mL or 2 mg/mL）are 25.8%，21.8%，55.4%，25.6%；44.6%，35.9%，55.5%，31.4%. While that of drug solution are 28.9% ，29.7% ，7.8% ，7.7%. The suppressive effects of the PFD loaded hydrogels on HTF proliferation followed a dose-dependent fashion and time-dependent fashion.【Conclusions】Such biocompatible copolymers hydrogel can be effectively used as an drug sustain released system. It can induce significant inhibition of HTF proliferation. With equal amount of drug，the inhibition effect of drug loaded gel was longer than that of drug solution.
ABSTRACT
This work provides an efficiency analysis of the LightForce space debris collision avoidance scheme in the current debris environment and describes a simulation approach to assess its impact on the long-term evolution of the space debris environment. LightForce aims to provide just-in-time collision avoidance by utilizing photon pressure from ground-based industrial lasers. These ground stations impart minimal accelerations to increase the miss distance for a predicted conjunction between two objects. In the first part of this paper we will present research that investigates the short-term effect of a few systems consisting of 20 kW class lasers directed by 1.5 m diameter telescopes using adaptive optics. The results found such a network of ground stations to mitigate more than 85 percent of conjunctions and could lower the expected number of collisions in Low Earth Orbit (LEO) by an order of magnitude. While these are impressive numbers that indicate LightForce's utility in the short-term, the remaining 15 % of possible collisions contain (among others) conjunctions between two massive objects that would add large amount of debris if they collide. Still, conjunctions between massive objects and smaller objects can be mitigated. Hence, we choose to expand the capabilities of the simulation software to investigate the overall effect of a network of LightForce stations on the long-term debris evolution. In the second part of this paper, we will present the planned simulation approach for that effort. For the efficiency analysis of collision avoidance in the current debris environment, we utilize a simulation approach that uses the entire Two Line Element (TLE) catalog in LEO for a given day as initial input. These objects are propagated for one year and an all-on-all conjunction analysis is performed. For conjunctions that fall below a range threshold, we calculate the probability of collision and record those values. To assess efficiency, we compare a baseline (without collision avoidance) conjunction analysis with an analysis where LightForce is active. Using that approach, we take into account that collision avoidance maneuvers could have effects on third objects. Performing all-on-all conjunction analyses for extended period of time requires significant computer resources; hence we implemented this simulation utilizing a highly parallel approach on the NASA Pleiades supercomputer.
