Polymeric Nanohydrogels of Poly(N-Isopropylacrylamide)Combined with Others Functionalized Monomers:Synthesis and Characterization

Nanohydrogels from inverse microemulsion (w/o) polymerization, at 25°C, of N-isopropylacrylamide (NIPA) and functionalized monomers are described. The functionalized monomers were: N-(pyridine-4-ylmethyl) acrylamide (NP4MAM) and tert-butyl 2-acrylamidoethyl carbamate (2AAECM). The polymeric nanohydrogel obtained was characterized by attenuated total reflectance Fourier-transformed infrared spectroscopy (ATR-FTIR) and proton nuclear magnetic resonance spectrometry (1HNMR), while their morphology and particle size was assessed by scanning electron microscopy (SEM) and dynamic light scattering. Their thermal properties were studied by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). As a preliminary measure of biocompatibility, in vitro evaluations of the nanohydrogels were carried out by cellular toxicity (colon carcinoma cells, CT-26) and hemocompatibility tests. These evaluations showed that these nanohydrogels were not toxic in the examined concentration range and exhibited preliminary blood compatibility;therefore they could be used in biomedical applications.

In vitro and in vivo biocompatibility of Mg–Zn–Ca alloy operative clip

At present,titanium(Ti)and its alloys are most commonly use in hemostasis clip clinical applications.However,the Ti Clip cannot be absorbed in human body and produce artifacts on computed tomography(CT),and induce clinically relevant hypersensitivity in patients.In order to overcome the drawbacks of the non-degradable Ti clips,an Mg-Zn-Ca alloy operative clip was fabricated by combining hot extrusion and blanking processing.In vitro and in vivo biocompatibility of Mg-Zn-Ca alloy operative clip were evaluated by L-929 Cells and SD rat model respectively.It was found that Mg-Zn-Ca alloy exhibited non-cytotoxic to L929 cells.In vivo implantation showed that the newly designed Mg-Zn-Ca clip can successfully ligated carotid artery and no blood leakage occurred post-surgery.During the period of the clip degradation,a small amount of H2 gas formation and no tissue inflammation around the clips were observed.The degradation rate of the clip near the heart ligated the arteries faster than that of clip far away the heart due do the effect of arterial blood.Histological analysis and various blood biochemical parameters in rat serum samples collected at different times after clip implantation showed no tissue inflammation around the clips.

Characteristics ofβ-type Ti-41Nb alloy produced by laser powder bed fusion:Microstructure,mechanical properties and in vitro biocompatibility

Aβ-type Ti-41 Nb alloy with high relative density has been successfully fabricated by laser powder bed fusion(L-PBF)using pre-alloyed powders for potential implant application.The homogeneous microstructure can be achieved in L-PBF fabricated(L-PBFed)Ti-41 Nb alloy but slight composition segregation was detected along molten pool boundaries.The L-PBFed alloy was dominated by typical epitaxial columnar grains with strong(001)grain orientation along building direction(BD),and cellular structure was distinguished within the columnar grains.The main reasons for this microstructure can be attributed to effective thermal gradient and epitaxial growth.L-PBFed alloy exhibited higher mechanical strength compared with cold rolling plus annealing(CRA)alloy due to the finer grains,dislocations accumulation and different TRIP behaviors,accompanied by good ductility.It also exhibited much lower thermal conductivity and better hydrophilic feature than those of CP-Ti.Besides,the L-PBFed alloy exhibited slightly better cell spread and cell proliferation rates compared with CP-Ti.Moreover,L-PBFed alloy presented better alkaline phosphatase(ALP)activities and extracellular matrix(ECM)mineralization,which suggests that the L-PBFed alloy can stimulate the osteogenic differentiation of rat bone mesenchymal stem cells.The Ti-41 Nb alloy,fabricated by L-PBF,reveals a good combination of mechanical properties,physicochemical properties and biocompatibility,exhibiting the great potential as the dental implant.

In Vivo and In Vitro Degradation Behavior of Magnesium Alloys as Biomaterials

The corrosion behavior of pure Mg,AZ31,and AZ91D were evaluated in various in vitro and in vivo environments to investigate the potential application of these metals as biodegradable implant materials.DC polarization tests and immersion tests were performed in different simulated body solutions,such as distilled（DI） water,simulated body fluid（SBF） and phosphate buffered solution（PBS）.Mg/Mg alloys were also implanted in different places in a mouse for in vivo weight loss and biocompatibility investigations.The in vivo subcutis bio-corrosion rate was lower than the corrosion rate for all of the in vitro simulated corrosive environments.The Mg/Mg alloys were biocompatible based on histology results for the liver,heart,kidney,skin and lung of the mouse during the two months implantation.Optical microscopy and scanning electron microscopy were carried out to investigate the morphology and topography of Mg/Mg alloys after immersion testing and implantation to understand the corrosion mechanisms.

Current Status and Outlook of Porous Zn-based Scaffolds for Bone Applications: A Review

Over the past 5 years,many works have been performed to reveal the potentials of Zinc(Zn)-based materials as temporary bone scaffolds with the expectation that their emergence could address some of the main concerns associated with magnesium-and iron-based materials.Thanks to the emerging Additive Manufacturing(AM)technology,it facilitates the optimization of the design and production of topological porous Zn-based materials suited for bone scaffolds.Since the studies on the porous Zn-based scaffolds are on the rise,we provide the most current progress in the development of porous Zn-based scaffolds for bone applications.The impacts of recently developed topological design from the AM as well as the advanced dynamic-flow corrosion on their corrosion,mechanical properties,and in vitro biocompatibility are also presented.Plus,we identify a number of research gaps and the challenges encountered in adopting porous Zn-based scaffolds for orthopedic applications and suggest some promising areas for future research.