Effects of Organic Montmorillonite (OMMT) and Pre-Orientation on Property of Poly(l-lactic acid) (PLLA)/Ethylene Propylene Diene Monomer (EPDM) Blends

Bioabsorbable zinc alloys for use in urological surgery

PURPOSE

Non-absorbable clips are widely used in urologic surgery and they may come in contact with an open urinary tract intraoperatively. As a result, stray clips in the urinary tract and associated intractable infections have been reported. We developed a bioabsorbable metal and evaluated whether it would dissolve if it strayed into the urinary tract.

METHODS

We prepared four types of alloys mainly comprising zinc (Zn) with small amounts of magnesium (Mg) and strontium (Sr), and the biological effects, degradability, strength, and ductility were investigated. Each alloy was implanted in the bladder of five rats for 4, 8, and 12 weeks. The alloys were removed and evaluated for degradability, stone adhesion, and tissue changes. The Zn-Mg-Sr alloy had degradability and no stone adhesion in the rat experiments, and it was implanted in the bladders of five pigs for 24 weeks. The Mg and Zn levels in the blood were measured, and staple changes were confirmed by cystoscopy.

RESULTS

Zn-Mg-Sr alloys showed the best degradability of 6.51% at 12 weeks. In pig experiments, the degradation rate was 3.72% at 24 weeks. None of the pigs had changes in the Zn or Mg concentrations in the blood. Overall, the bladder incision was healed and the gross pathology showed wound healing.

CONCLUSIONS

The Zn-Mg-Sr alloys were safely used in animal experiments. Furthermore, the alloys are easy to process and can be formed into various shapes, such as staples, making them useful in robotic surgery.

Preparation and Properties of Poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate)/Polyglycolic Acid (PETG/PGA) Blends

Polyglycolic acid (PGA) is used as a reinforcing component to enhance the mechanical properties of poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG). The tensile performance, micromorphology, crystallinity, heat resistance, and melt mass flow rates (MFRs) of PETG/PGA blends with varying PGA contents were studied. Both the tensile yield strength and tensile modulus of the PETG/PGA blends increased gradually with an increase in the PGA content from 0 to 35 wt%. The tensile yield strength of the PETG/PGA (65/35) blend increased by 8.7% (44.38 to 48.24 MPa), and the tensile modulus increased by 40.2% (1076 to 1509 MPa). However, its tensile ductility decreased drastically, owing to the poor interfacial compatibility of PETG/PGA and the oversized PGA domains. A multiple epoxy chain extender (ADR) was introduced into the PETG/PGA (65/35) blend to improve its interfacial compatibility and rheological properties. The tensile performance, micromorphology, rheological properties, crystallinity, and heat resistance of PETG/PGA (65/35) blends with varying ADR contents were studied. The strong chain extension effect of ADR along with its reactive compatibilization improved the rheological properties and tensile ductility. By carefully controlling the ADR concentration, the performance of PETG/PGA blends can be regulated for different applications.