Optimizing fabrication parameters via Taguchi method for production of high yield hydroxyapatite microsphere scaffolds using Drop-on-Demand inkjet method

Phosphoramide Hydrogels as Biodegradable Matrices for Inkjet Printing and Their Nano-Hydroxyapatite Composites

Inkjet printing is a leading technology in the biofabrication of three-dimensional biomaterials, offering digital, noncontact deposition with micron-level precision. Among these materials, hydroxyapatite is widely recognized for its use in bone tissue engineering. However, most hydroxyapatite-laden inks are unsuitable for inkjet printing. To address this, we developed photocurable and biodegradable phosphoramide-based hydrogels containing thiol-functionalized polyethylene glycol via click chemistry. These hydrogels degrade into phosphates, the natural component of bone. The rheological properties of the inks are finely tuned through chemical design to meet the requirements of nanohydroxyapatite composite inks for piezoelectric inkjet printing. We demonstrated their printability using simple geometric patterns, showcasing a versatile and efficient solution for the precise inkjet printing of biomaterial composites.

Characterization and in-vitro assessment of silicon-based apatite microspheres for bone tissue engineering applications

In the field of bone tissue engineering, silicon (Si) has been found as an essential element for bone growth. However, the use of silicon in bioceramics microspheres remains limited. In this work, different weight percentages (0.8, 1.6, and 2.4 wt %) of silicon was incorporated into hydroxyapatite and fabricated into microspheres. 2.4 wt % of Si incorporated into HAp microspheres (2.4 SiHAp) were found to enhance functional properties of the microspheres which resulted in improved cell viability of human mesenchymal stem cells (hMSCs), demonstrating rapid cell proliferation rates resulting in high cell density accumulated on the surface of the microspheres which in turn permitted better hMSCs differentiation into osteoblasts when validated by bone marker assays (Type I collagen, alkaline phosphatase, osteocalcin, and osteopontin) compared to apatite microspheres of lower wt % of Si incorporated and non-substituted HAp (2.4 SiHAp >1.6 SiHAp >0.8 SiHAp > HAp). SEM images displayed the densest cell population on 2.4 SiHAp surfaces with the greatest degree of cell stretching and bridging between neighboring microspheres. Incorporation of silicon into apatite microspheres was found to accelerate the rate and number of apatite nucleation sites formed when subjected to physiological conditions improving the interface between the microsphere scaffolds and bone forming cells, facilitating better adhesion and proliferation.