Porous calcium phosphate glass microspheres for orthobiologic applications

Orthobiologics is a rapidly advancing field utilising cell-based therapies and biomaterials to enable the body to repair and regenerate musculoskeletal tissues. This paper reports on a cost-effective flame spheroidisation process for production of novel porous glass microspheres from calcium phosphate-based glasses to encapsulate and deliver stem cells. Careful selection of the glass and pore-forming agent, along with a manufacturing method with the required processing window enabled the production of porous glass microspheres via a single-stage manufacturing process. The morphological and physical characterisation revealed porous microspheres with tailored surface and interconnected porosity (up to 76 ± 5%) with average pore size of 55 ± 8 µm and surface areas ranging from 0.34 to 0.9 m² g^-1. Furthermore, simple alteration of the processing parameters produced microspheres with alternate unique morphologies, such as with solid cores and surface porosity only. The tuneable porosity enabled control over their surface area, degradation profiles and hence ion release rates. Furthermore, cytocompatibility of the microspheres was assessed using human mesenchymal stem cells via direct cell culture experiments and analysis confirmed that they had migrated to within the centre of the microspheres. The novel microspheres developed have huge potential for tissue engineering and regenerative medicine applications.

STATEMENT OF SIGNIFICANCE

This manuscript highlights a simple cost-effective one-step process for manufacturing porous calcium phosphate-based glass microspheres with varying control over surface pores and fully interconnected porosity via a flame spheroidisation process. Moreover, a simple alteration of the processing parameters can produce microspheres which have a solid core with surface pores only. The tuneable porosity enabled control over their surface area, degradation profiles and hence ion release rates. The paper also shows that stem cells not only attach and proliferate but more importantly migrate to within the core of the porous microspheres, highlighting applications for bone tissue engineering and regenerative medicine.

Analysis of the in vitro degradation and the in vivo tissue response to bi-layered 3D-printed scaffolds combining PLA and biphasic PLA/bioglass components - Guidance of the inflammatory response as basis for osteochondral regeneration

The aim of the present study was the in vitro and in vivo analysis of a bi-layered 3D-printed scaffold combining a PLA layer and a biphasic PLA/bioglass G5 layer for regeneration of osteochondral defects in vivo Focus of the in vitro analysis was on the (molecular) weight loss and the morphological and mechanical variations after immersion in SBF. The in vivo study focused on analysis of the tissue reactions and differences in the implant bed vascularization using an established subcutaneous implantation model in CD-1 mice and established histological and histomorphometrical methods. Both scaffold parts kept their structural integrity, while changes in morphology were observed, especially for the PLA/G5 scaffold. Mechanical properties decreased with progressive degradation, while the PLA/G5 scaffolds presented higher compressive modulus than PLA scaffolds. The tissue reaction to PLA included low numbers of BMGCs and minimal vascularization of its implant beds, while the addition of G5 lead to higher numbers of BMGCs and a higher implant bed vascularization. Analysis revealed that the use of a bi-layered scaffold shows the ability to observe distinct in vivo response despite the physical proximity of PLA and PLA/G5 layers. Altogether, the results showed that the addition of G5 enables to reduce scaffold weight loss and to increase mechanical strength. Furthermore, the addition of G5 lead to a higher vascularization of the implant bed required as basis for bone tissue regeneration mediated by higher numbers of BMGCs, while within the PLA parts a significantly lower vascularization was found optimally for chondral regeneration. Thus, this data show that the analyzed bi-layered scaffold may serve as an ideal basis for the regeneration of osteochondral tissue defects. Additionally, the results show that it might be able to reduce the number of experimental animals required as it may be possible to analyze the tissue response to more than one implant in one experimental animal.