Effect of Cu- and Zn-Doped Bioactive Glasses on the In Vitro Bioactivity, Mechanical and Degradation Behavior of Biodegradable PDLLA Scaffolds

Abstract

Biodegradable polymer scaffolds filled with bioactive glass particles doped with therapeutic metal ions are a novel and promising strategy to repair critical-sized bone defects. In this study, scaffolds based on a poly (D, L-lactide acid) (PDLLA) matrix filled with un-doped and Cu-, Zn- and CuZn-doped bioactive glass particles were produced by freeze-drying and a salt-leaching method. The effects of the doping and content of the glass particles (10 and 30 wt.%) on the morphology, compression properties, apatite formation, and degradation behavior of the scaffolds were evaluated. The scaffolds presented high porosity (~93%) with pores ranged from 100 to 400 μm interconnected by smaller pores and this porosity was kept after the glass particles incorporation. The glass particles reinforced the polymer scaffolds with improvements as high as 130% in elastic moduli, and further promoted the apatite formation on the scaffold surface, both properties depending on the amount and type of filler. The bioactive glass particles boosted the scaffold degradation with the PDLLA/un-doped glass scaffold showing the highest rate, but still retaining structural and dimensional integrity. Our findings show that the incorporation of un-doped and metal-doped bioactive glasses increases the mechanical strength, promotes the bioactivity and modifies the degradation profile of the resulting polymer/glass scaffolds, making them better candidates for bone repair.

Three-dimensionally printed polycaprolactone/multicomponent bioactive glass scaffolds for potential application in bone tissue engineering

“…The pH of the solution increased during the incubation time, especially within the first day of soaking. The increase in pH values is related to the partial dissolution of the glass during the stages of the bioactivity process associated with the formation of a HAp layer on the surface of the 3D printed scaffolds, which in line with previous studies [46][47][48].…”

Recent progress on polymer scaffolds production: Methods, main results, advantages and disadvantages

“…The ability to maintain the porous structure and mechanical properties during the generation of the cellular matrix and mineralization process is desirable. In this way, degradation studies in phosphate buffer solution (PBS) showed that the scaffolds lost almost 10% of their initial weights after 120 days of immersion [17]. In vitro tests performed in a previous study [21] showed cytocompatibility of the scaffolds against bone marrow stromal cells (ST-2), and its good angiogenic and osteogenic properties.…”

“…The pore diameter can be controlled by the size of the salt crystals, allowing pore interconnection and resulting in a very reproducible technique. However, this method has some disadvantages; for example, some degradation may occur when the material is exposed to water, and it is difficult to guarantee the complete removal of salt from samples [5,17]. Another shortcoming of this method is that it only allows the production of samples up to 3 mm thick [18]; besides that, sizes, dimensions, and shapes are limited by the mold in which the system polymer salt was poured.…”

“…However, complex shapes are not indicated, once the evaporation of the solvent and complete removal of soluble particles inside the scaffold will be harmed. The most common leachable slat porogen is sodium chloride (NaCl) [5,17] due to its high solubility in water. However, other salts have been studied, such as copper sulfate (Cu 2 SO 4 ) [4] and ammonium carbonate ((NH 4 ) 2 CO 3 ) [19] or organic particles such as sucrose.…”

“…The salt leaching method has been used exclusively or combined with other techniques (e.g. 3D printing and solvent casting) to cartilage [20] and bone tissue engineering [5,17]. Figure 1a shows the simplified scheme of a typical salt leaching process.…”