Jan Chłopek

Carbon composite material and polysulfone modified by nano-hydroxyapatite

Abstract This paper reports on mechanical and biological properties of carboncarbon1 composites and polysulfone modified by hydroxyapatite (HAP), both natural (nano-particles) and synthetic (micro-particles) minerals. Results show that carbon-HAP composites have mechanical properties similar to carbon-carbon composites, while addition of HAP to polysulfone causes advantageous growth of Young’s modulus and limitation of creep, and disadvantageous decrease of tensile strength. Tests performed in simulated body fluid for carbon-HAP and polysulfone- HAP composites prove that the process of hydroxyapatite build-up becomes most intensive in the case of composites with nano-particles originating from natural hydroxyapatite.

Polylactide/polycaprolactone asymmetric membranes for guided bone regeneration

Abstract The aim of this work was to develop bioresorbable, asymmetric membranes for guided bone regeneration (GBR). Two resorbable polymers – polylactide (PLA) and polycaprolactone (PCL) were used in fabrication process. Two different manufacturing methods were applied: electrospinning in the case of PLA and freeze-drying of PCL. Mechanical properties, stability in a water environment and biocompatibility of fabricated membranes were evaluated. Microstructure [scanning electron microscopy (SEM)] of the membranes was assessed in terms of level of porosity, as well as size and shape of the pores. Study showed that combination of electrospinning and freeze-drying methods allows biocompatible PLA/PCL bi-phasic materials of appropriate mechanical properties and diverse microstructure to be produced, that should on the one hand prevent soft tissue growth, and on the other hand be a suitable scaffold for the growth of bone cells.

Magnesium alloy wires as reinforcement in composite intramedullary nails

A promising group of biomaterials assigned for the production of intramedullary nails are composites with a polylactide (PLA) matrix, reinforced with wires made of magnesium alloys and carbon fibres. The paper describes the effect of the composition of magnesium alloy wires, their number and orientation in the composite, as well as their connection with differently directed long carbon fibres, on the mechanical properties and the degradation rate of the obtained intramedullary nails. Among the tested implant prototypes, the best mechanical characteristics and a gradual and uniform course of magnesium alloy wires were exhibited by the PLA+CF1D+MgI composite nails (with a unidirectional orientation of carbon fibres and an axially oriented single Mg alloy wire). The strength of these nails became gradually decreased with the incubation time, which should allow for a gradual loading of the bone. In the case of the PLA with only magnesium alloy wires (without carbon fibres), the increase of the number of wires, on the one hand, stimulates the improvement of the nails strength, yet on the other hand, a higher content of magnesium alloys in the PLA matrix affects the nails faster resorption.

Mechanical properties and dynamics of degradation of polylactide matrix composites with calcium and sodium alginate fibers

In the present article, new polylactide/alginate fibers composites were investigated. Composite pre-pregs were made by solution casting method. The aim of the study was to define physico-mechanical properties of developed materials. The scope of the studies included: examining the static mechanical properties, properties of the surface and their changes during degradation. Moreover, intensity of the release of degradation products to the environment and a change of the mass of examined samples were analyzed. Obtained results were evaluated taking into account possibility to use prepared composited as materials for vascular implants.

Chitosan-Based Hydrogels: Preparation, Properties, and Applications

Chitosan is a hydrophilic polysaccharide obtained by partial deacetylation of chitin, which is one of the most popular biopolymers. Chitosan is well known for its favorable properties including biocompatibility, biodegradability, antibacterial, and biological activity, as well as its renewable character. Thanks to those features chitosan’s popularity in various applications ranging from food industry to tissue engineering is constantly growing. The following chapter will more closely consider fabrication, properties, and specific applications of chitosan-based hydrogel networks. Methods for chitosan preparation will be summarized, followed by detailed characterization of chitosan properties. Strategies for their improvement and fabrication of chitosan derivatives will be discussed as well. Next, attention will be drawn to preparation of chitosanbased hydrogels via chitosan crosslinking. Both chemical and physical crosslinking methods will be considered with special emphasis on comparison between the two crosslinking methods and recent advancements in application of novel biocompatible crosslinkers. This chapter will also take a closer look at formation of stimuli-responsive (especially pHand temperature-sensitive systems) and injectable hydrogels. Utilization of chitosan hydrogels in tissue engineering will be highlighted together with different techniques for fabrication and construction of three-dimensional scaffolds. Finally, other applications of chitosan-based hydrogels and their composites will be summarized.

The influence of bioactive additives on polylactide accelerated degradation

Abstract The aim of the research was to study the influence of the bioactive modifiers such as 7 wt.% of micrometric tricalcium phosphate (TCP) and 0.3 wt.% of nanometric hydroxyapatite (HAP) on the accelerated degradation process of composite resorbable implants based on poly(L-lactide) (PLA) matrix. The degradation was assessed on the basis of microstructural, structural and mechanical alterations. The measure of the PLA degradation progress was the gradual decrease in its molecular weight and mechanical strength. As the degradation proceeded, the plastic properties of materials decreased. In the case of composites such changes took place faster, which implies the accelerating influence of modifiers on the degradation process. Moreover, modifiers act as crystallization seeds, accelerating and stimulating the matrix organization and appearance of crystalline areas. The properties of the two composites differ. Adding TCP alone influenced the structural changes in the polymer more significantly than the addition of TCP/HAP, thus affecting the faster degradation.