Wojciech Prochwicz

Scaffolds with shape memory behavior for the treatment of large bone defects

The aim of the presented study was preparation, analysis of properties, and in vitro characterization of porous shape-memory scaffolds, designed for large bone defects treatment using minimally invasive surgery approach. Biodegradable terpolymers of l-lactide/glycolide/trimethylene carbonate (LA/GL/TMC) and l-lactide/glycolide/ε-caprolactone (LA/GL/Cap) were selected for formulation of these scaffolds. Basic parameters of shape memory behavior (i.e. recovery ratio, recovery time) and changes in morphology (SEM, average porosity) and properties (surface topography, water contact angle, compressive strength) during shape memory cycle were characterized. The scaffolds preserved good mechanical properties (compressive strength about 0.7 to 0.9 MPa) and high porosity (more than 80%) both in initial shape as well as after return from compressed shape. Then the scaffolds in temporary shape were inserted into the model defect of bone tissue at 37°C. After 12 min the defect was filled completely as a result of shape recovery process induced by body temperature. The scaffold obtained from LA/GL/TMC terpolymer was found the most prospective for the planned application thanks to its appropriate recovery time, high recovery ratio (more than 90%), and cytocompatibility in contact with human osteoblasts and chondrocytes.

Local delivery system of doxycycline hyclate based on ϵ-caprolactone copolymers for periodontitis treatment

The aim of the study was to evaluate kinetics of doxycycline hyclate release from polymeric bioresorbable implants and to examine suitability of this system for local treatment of periodontitis. Selected trimethylene carbonate/ϵ-caprolactone (TMC/CL) and glycolide/caprolactone (GL/CL) copolymers were synthesized and used as carriers in the form of small elastic rings with 5 wt% and 10 wt% doxycycline hyclate content, or in the form of flakes obtained through electro-spinning technique. The release of the drug under in vitro conditions has been tested. The study has shown that equimolar TMC/CL copolymer loaded with 10 wt% of doxycycline hyclate appears to be the most suitable copolymer for assumed system. The drug release proceeds mainly by diffusion of medium into the polymeric matrix and then the drug is washed out. Daily validation of doxycycline doses released by the system should ensure accurate course of the therapy.

Influence of Radiation Sterilization on Properties of Biodegradable Lactide/Glycolide/Trimethylene Carbonate and Lactide/Glycolide/ε-caprolactone Porous Scaffolds with Shape Memory Behavior

The aim of the study was the evaluation of gamma irradiation and electron beams for sterilization of porous scaffolds with shape memory behavior obtained from biodegradable terpolymers: poly(l-lactide-co-glycolide-co-trimethylene carbonate) and poly(l-lactide-co-glycolide-co-ɛ-caprolactone). The impact of mentioned sterilization techniques on the structure of the scaffolds before and after the sterilization process using irradiation doses ranged from 10 to 25 kGy has been investigated. Treatment of the samples with gamma irradiation at 15 kGy dose resulted in considerable drop in glass transition temperature (Tg) and number average molecular weight (Mn). For comparison, after irradiation of the samples using an electron beam with the same dose, no significant changes in structure or properties of examined scaffolds have been noticed. Higher doses of irradiation via electron beam caused essential changes of the scaffolds’ pores resulting in partial melting of their surface. Nevertheless, obtained results have revealed that sterilization with electron beam, when compared to gamma irradiation, is a better method because it does not affect significantly the physicochemical properties of the scaffolds. Both used methods of sterilization did not influence the shape memory behavior of the examined materials.

Hydrogen permeation properties of Pd-coated Pd33Ni52Si15 amorphous alloy membrane

Abstract The vast majority of experimental techniques used for the measurements of hydrogen permeability through metallic membranes whose one or both surfaces are covered with a thin Pd film is based on the assumption that a ratio of film-to-membrane thickness is small enough to cause hydrogen flow to be independent of the Pd film thickness. In an attempt to verify this assumption, we have measured the hydrogen flow through the Pd33Ni52Si15 amorphous membrane covered with Pd film of 10, 20, and 30 nm in thickness. Contrary to our expectations, we have found a dramatic decrease in hydrogen flow with the increase in Pd film thickness. Our findings are discussed in terms of potential barrier between the two different phases.

Electrical conductivity of Pd47Ni47Si6 amorphous membrane while hydrogen permeation

Hydrogen diffusion through an amorphous membrane causes local disorders in the structure which can be detected through the measurement of changes of the electrical conductivity. Detecting these changes and comparing them directly with the amount of the permeated hydrogen provides information on the efficiency of separation, which can be used in hydrogen sensor and analyzer technology. This paper presents the results of electrical resistivity measurement of Pd47Ni47Si6 alloy amorphous membrane while hydrogen permeation flux was being changed along with the temperature. It was found that hydrogen changes the nature of the resistivity and the temperature coefficient of resistivity is negative, however, starting from the temperature of 365 K, its value becomes smaller. In order to explain this phenomenon thorough and detailed measurements of phase transitions were made with the use of differential scanning calorimetry and X-ray diffractometry. On the basis of the research an attempt was made to explain the recorded changes of electrical conductivity.