Advent of additive manufacturing in biomedical field has nurtured fabrication of complex, customizable and reproducible orthopaedic implants. Layer-by-layer deposition of biodegradable polymer employed in development of porous orthopaedic screws promises gradual dissolution and complete metabolic resorption thereby overcoming the limitations of conventional metallic screws. In the present study, screws with different pore sizes (916 × 918 μm to 254 × 146 μm) were 3D printed at 200 μm layer height by varying printing parameters such as print speed, fill density and travel speed to augment the bone ingrowth. Micro-CT analysis and scanning electron micrographs of screws with 45% fill density confirmed porous interconnections (40.1%) and optimal pore size (259 × 207 × 200 μm) without compromising the mechanical strength (24.58 ± 1.36 MPa). Due to the open pore structure, the 3D printed screws showed increased weight gain due to the deposition of calcium when incubated in simulated body fluid. Osteoblast-like cells attached on screw and infiltrated into the pores over 14 days of in vitro culture. Further, the screws also supported greater human mesenchymal stem cell adhesion, proliferation and mineralized matrix synthesis over a period of 21 days in vitro culture as compared to non-porous screws. These porous screws showed significantly increased vascularization in a rat subcutaneous implantation as compared to control screws. Porous screws produced by additive manufacturing may promote better osteointegration due to enhanced mineralization and vascularization.

Damage to intervertebral discs (IVD) can lead to chronic pain and disability, and no current treatments can fully restore their function. Some non-surgical treatments have shown promise; however, these approaches are generally limited by burst release and poor localization of diverse molecules. In this proof-of-concept study, we developed a nanoparticle (NP) delivery system to efficiently deliver high- and low-solubility drug molecules. Nanoparticles of cellulose acetate and polycaprolactone-polyethylene glycol conjugated with 1-oxo-1H-pyrido [2,1-b][1,3]benzoxazole-3-carboxylic acid (PBC), a novel fluorescent dye, were prepared by the oil-in-water emulsion. Two drugs, a water insoluble indomethacin (IND) and a water soluble 4-aminopyridine (4-AP), were used to study their release patterns. Electron microscopy confirmed the spherical nature and rough surface of nanoparticles. The particle size analysis revealed a hydrodynamic radius ranging ~150–162 nm based on dynamic light scattering. Zeta potential increased with PBC conjugation implying their enhanced stability. IND encapsulation efficiency was almost 3-fold higher than 4-AP, with release lasting up to 4 days, signifying enhanced solubility, while the release of 4-AP continued for up to 7 days. Nanoparticles and their drug formulations did not show any apparent cytotoxicity and were taken up by human IVD nucleus pulposus cells. When injected into coccygeal mouse IVDs in vivo, the nanoparticles remained within the nucleus pulposus cells and the injection site of the nucleus pulposus and annulus fibrosus of the IVD. These fluorescent nano-formulations may serve as a platform technology to deliver therapeutic agents to IVDs and other tissues that require localized drug injections.