In vivo degradability and biocompatibility of a rheo-formed Mg–Zn–Sr alloy for ureteral implantation

The introduction of biodegradable implant materials has significantly improved the postoperative subjective feelings of patients within the past few decades,among which magnesium alloy is widely considered a favorable choice as its appropriate biodegradability and evident antibacterial activity.Here,we reveal a semisolid rheo-formed Mg–Zn–Sr alloy ureteral implant that displayed suitable degradability and biocompatibility in a pig model.Refined non-dendritic microstructure was observed in the rheo-formed alloy,which led to ca.47%increase in ultimate tensile strength(from 195.0 MPa to 288.1 MPa)and more homogeneous degradation process compared with the untreated alloy.No post-interventional inflammation or pathological changes of the test animals were observed during the implantation period,and the corrosion rate(0.22±0.04 mm·y^(-1))perfectly fitted the clinical ureteral stent indwelling time.The urine bacteria numbers decreased from 88±13 CFU·mL^(-1)at 7 weeks post operation to 59±8 CFU·mL^(-1)at 14 weeks post operation,which confirmed the evident antibacterial activity of the alloy.Our study demonstrates that the Mg–Zn–Sr alloy is clinically safe for urinary system,enabling its efficacious use as ureteral implant materials.

In vivo urinary compatibility of Mg-Sr-Ag alloy in swine model

A biodegradable metallic ureteral stent with suitable mechanical properties and antibacterial activity remains a challenge.Here we reveal the scientific significance of a biodegradable Mg-Sr-Ag alloy with a favorable combination of balanced mechanical properties,adjustable indwelling time in urinary tract and evident antibacterial activity via in vivo experiments in a swine model.Attributed to the rheo-solidification process,equiaxial microstructure and significantly refined grains(average grain size:27.1μm)were achieved.Mg17Sr2 and Mg4Ag were found as the primary precipitates in the matrix,due to which the alloy obtained ca.111%increase in ultimate tensile strength in comparison to pure magnesium.Both the in vitro and in vivo results demonstrated the satisfactory biocompatibility of the alloy.Histological evaluation and bioindicators analysis suggested that there was no tissue damage,inflammation and lesions in the urinary system caused by the degradation process.The stent also improved the post-operative bladder functions viewed from the urodynamic results.Our findings highlight the potential of this alloy as antibacterial biodegradable urinary implant material.