Poly(lactide-co-glycolide)-bilayered scaffolds with the same porosity or different ones on the two layers were fabricated,and the porosity effect on in vivo repairing of the osteochondral defect was examined in a comparative way for the first time.The constructs of scaffolds and bone marrow-derived mesenchymal stem cells were implanted into pre-created osteochondral defects in the femoral condyle of New Zealand white rabbits.After 12 weeks,all experimental groups exhibited good cartilage repairing according to macroscopic appearance,cross-section view,haematoxylin and eosin staining,toluidine blue staining,immunohistochemical staining and real-time polymerase chain reaction of characteristic genes.The group of 92%porosity in the cartilage layer and 77%porosity in the bone layer resulted in the best efficacy,which was understood by more biomechanical mimicking of the natural cartilage and subchondral bone.This study illustrates unambiguously that cartilage tissue engineering allows for a wide range of scaffold porosity,yet some porosity group is optimal.It is also revealed that the biomechanical matching with the natural composite tissue should be taken into consideration in the design of practical biomaterials,which is especially important for porosities of a multi-compartment scaffold concerning connected tissues.
Poly(lactic acid) (PLA) and other aliphatic polyesters containing the unit of lactic acid are very popular biodegradable materials. While the degradation products, lactic acids, have been worried to bring with negative influence on biocompatibility, the focused experimental studies are less reported. This study is aimed at an in vitro examination of cytotoxicity of both L-lactic acid and D,L-lactic acid. Mesenchymal stem cells (MSCs) derived from rat bone marrow are employed to test the cytotoxicity of the lactic acids. Considering that the addition of lactic acids not only introduces lactate groups but also alters medium pH and ion strength, these three candidate effects are examined in a decoupled way by setting different comparison groups. The results confirm that the change of medium pH is the predominant factor. It has also been found that D-lactate is more cytotoxic than L-lactate at high concentrations. Yet, either L-or D,L-lactic acids seem acceptable in most of medical applications, because the cytotoxicity is significant only when the concentrations are as high as 20 mmol/L for both of them.
Based on the noncovalent functionalization of ferrocene-grafted polyethylenimine （PEI-Fc） and carbon nanotubes （CNTs）, CNT bundles are exfoliated by PEI-Fc solution and thus form stable compounds PEI-Fc@CNTs, which is used to construct the PEI-Fc@CNTs/DNA multilayers through layer-by-layer assembly. The multilayers show a highly uniform and homogeneous characteristic, which significantly improve the electrical property of the multilayers. Upon the oxidation electrical potential, the ferrocene groups are switched from reduction state （[Fe（C5H5）2]） to oxidation state （[Fe（C5H5）2]^＋）, leading to change of microenvironments＇ charge density, resulting in swelling of the multilayers and a final degree of swelling of 37 % and the decrease of multilayer stiffness. We maintain that electrochemical control over the swelling behavior of multilayers could have important implications for responsive coatings of nanoscale devices, including mechanically tunable surfaces which are used to modulate cellular activities and control drug delivery.
The emergence of nanoparticles(NPs)has attracted tremendous interest of the scientific community for decades due to their unique properties and potential applications in diverse areas,including drug delivery and therapy.Many novel NPs have been synthesized and used to reduce drug toxicity,improve bio-availability,prolong circulation time,control drug release,and actively target to desired cells or tissues.However,clinical translation of NPs with the goal of treating particularly challenging diseases,such as cancer,will require a thorough understanding of how the NP properties influence their fate in biological systems,especially in vivo.Many efforts have been paid to studying the interactions and mechanisms of NPs and cells.Unless deliberately designed,the NPs in contact with biological fluids are rapidly covered by a selected group of biomolecules especially proteins to form a corona that interacts with biological systems.In this view,the recent development of NPs in drug delivery and the interactions of NPs with cells and proteins are summarized.By understanding the protein-NP interactions,some guidelines for safety design of NPs,challenges and future perspectives are discussed.
