Preparation, Degradation And Cytocompatability Of Nest-like Patterned Electrospun PLGA And PLGA/β-TCP Scaffolds

Scaffolds fabricated via electrospinning could mimick Extracelluar matrix well and become study hotspots in tissue engineering.In vitro evaluation of degradation properties of electrospun scaffolds is an inevitable procedure before further biodegradations and long-term success in vivo.The preparation,degradation,and cytocompatibility of nest-like patterned electrospun PLGA and PLGA/β-TCP scaffolds were studied in this thesis.Firstly,nest-like patterned electrospun PLGA(75/25) scaffold was fabricated by electrospinning using grid copper wires as collector.The as-electrospun nest-like patterned PLGA scaffolds were composed of numerous nest-like units(400×300μm),which had three typical regions with different topography:ridge-like region,non-woven region and magnetic lines-like region.Fiber diameters in the three regions were almost the same (849±118 nm),but fiber orientation and pore size were significantly different from each other.Secondly,in vitro hydrolytic and enzymatic degradation of nest-like patterned PLGA(75/25) scaffolds were carried out in phosphate buffer solution(PBS,pH 7.4,37℃) and PBS(7.4,37℃)with lysozyme(20000U/ml) in it.Results indicated that the robust framework of nest-like units had prevented the scaffolds from shrinking drastically and contributed to the maintainance of mechanical properties with degradation.Both hydrolytic and enzymatic degradation of PLGA nanofibrous scaffolds could be divided into two stages.In the first stage,the molecular weight of the samples decreased continuously with degradation time,whereas little weight loss occurred at this stage.But in the second stage,the molecular weight decreased to a low value and changed little with time,while the samples experienced significant weight loss.After hydrolysis for 20 weeks,nanofibers with porous inner but intact surface were detected.All these results indicated that an autocatalytic effect still existed in the hydrolysis of PLGA nanofibers(～900 nm).The degradation of PLGA(75:25) nanofibers in the presence of lysozyme was primarily a hydrolysis process and lysozyme had no accelerating effect on the cleavage of ester bond.The third,PLGA/β-TCP(90/10,80/20) composite scaffolds were prepared by electrospinning.Results indicated thatβ-TCP particles were successfully enwrapped in PLGA nanofibers and formed composite scaffolds. The tensile strength and modulus of as-spun PLGA/β-TCP nanofibrous scaffolds reached 5.35MPa and 120MPa respectively and decreased with degradation within 8 weeks.Weight,molecular weight of PLGA,decreased continuously with degradation for the three kinds of scaffolds.However, increased content ofβ-TCP in PLGA/β-TCP composite slowed down the degradation rate of PLGA component,decreased the acidity and increased concentration of Ca²⁺ in degradation medieum.MTT results indicated that cytocompatibility were also improved with increased content ofβ-TCP. Therefore,PLGA/β-TCP composite scaffolds with appropriate mechanical properties,adjustable degradeation rate and preferable cytocompatibility will be potential candidate for tissue engineering.