Magnesium and its alloys are being paid much attention recently as temporary implants,such as orthopedic implants and cardiovascular stents.However,the rapid degradation of them in physiological environment is a major obstacle preventing their wide applications to date,which will result in rapid mechanical integrity loss or even collapse of magnesium-based implants before injured tissues heal.Moreover,rapid degradation of the magnesium-based implants will also cause some adverse effects to their surrounding environment,such as local gas cavity around the implant,local alkalization and magnesium ion enrichment,which will reduce the integration between implant and tissue.So,in order to obtain better performance of magnesium-based implants in clinical trials,special alloy designs and surface modifications are prerequisite.Actually,when a magnesium-based implant is inserted in vivo,corrosion firstly happens at the implant-tissue interface and the biological response to implant is also determined by the interaction at this interface.So the surface properties,such as corrosion resistance,hemocompatibility and cytocompatibility of the implant,are critical for their in vivo performance.Compared with alloy designs,surface modification is less costly,flexible to construct multi-functional surface and can prevent addition of toxic alloying elements.In this review,we would like to summarize the current investigations of surface modifications of magnesium and its alloys for biomedical application.The advantages/disadvantages of different surface modification methods are also discussed as a suggestion for their utilization.
There are several limitations to the application of nanoparticles in the treatment of cancer,including their low drug loading,poor colloidal stability,insufficient tumor penetration,and uncontrolled release of the drug.Herein,gelatin/laponite(LP)/doxorubicin(GLD)nanoparticles are developed by crosslinking LP with gelatin for doxorubicin delivery.GLD shows high doxorubicin encapsulation efficacy(99%)and strong colloidal stability,as seen from the unchanged size over the past 21 days and reduced protein absorption by 48-fold compared with unmodified laponite/doxorubicin nanoparticles.When gelatin from 115 nm GLD reaches the tumor site,matrix metallopeptidase-2(MMP-2)from the tumor environment breaks it down to release smaller 40 nm LP nanoparticles for effective tumor cell endocytosis.As demonstrated by superior penetration in both in vitro three-dimensional(3D)tumor spheroids(138-fold increase compared to the free drug)and in vivo tumor models.The intracellular low pH and MMP-2 further cause doxorubicin release after endocytosis by tumor cells,leading to a higher inhibitory potential against cancer cells.The improved anticancer effectiveness and strong in vivo biocompatibility of GLD have been confirmed using a mouse tumor-bearing model.MMP-2/pH sequentially triggered anticancer drug delivery is made possible by the logical design of tumor-penetrating GLD,offering a useful method for anticancer therapy.
The well-densified Ni3Al-0.5B-5Cr alloy was fabricated by self-propagation high-temperature synthesis and extrusion technique. Microstructure examination shows that the synthesized alloy has fine microstructure and contains Ni3Al, Al2O3, Ni3B and Cr3Ni2 phases. Moreover, the self-propagation high-temperature synthesis and extrusion lead to great deformation and recrystallization in the alloy, which helps to refine the microstructure and weaken the misorientation. In addition, the subsequent extrusion procedure redistributes the Al2O3 particles and eliminates the γ-Ni phase. Compared with the alloy synthesized without extrusion, the Ni3Al-0.5B-5Cr alloy fabricated by self-propagation high-temperature synthesis and extrusion has better room temperature mechanical properties, which should be ascribed to the microstructure evolution.
We present P(TMC-co-DLLA)copolymer with the molar ratio of TMC:DLLA紏15:85 was used to systematic study of in vivo and in vitro degradation behaviors.Dense homogeneous copolymer specimens were prepared by compression molding method.The in vitro and in vivo degradation were,respectively,performed at simulative body condition and implanted into rat’s subcutaneous condition.Investigations were followed via physicochemical and histological analysis such as SEM,GPC,DSC,FTIR and H&E stain.The results demonstrate that copolymeric material can degrade in phosphate buffer solution(PBS)and in rat’s body,and the in vivo degradation rate is faster.Obvious decline of molecule weight and mass loss has been observed,which led to the attenuation of mechanical strength.Furthermore,apart from the hydrolysis,macrophagocytes took part in the phagocytosis in vivo,indicating that degradation rate could be regulated by the combinational mechanism.It is concluded that P(TMC-co-DLLA)copolymer is a promising candidate for tissue repair.
