Table 2.

Biomaterials in recent use for non-viral delivery systems and their benefits.

Biomaterial(s) for Matrix	Delivery System/Model	Key Features	Advantages	References
Chitosan, Col1agen	Peptide derived BMP-9 (pBMP-9)	Derived from recombinant BMP-9 (rhBMP-9). Higher concentrations (400 ng/ml) inhibits murine preosteoblasts cell proliferation. Low concentration (less than 100 ng/ml) highlighted the promising results in comparison to rhBMP-9 and rhBMP-2. Chitosan as a carrier for pBMP-9 is more effective over type I collagen constructs in terms of release kinetics of pBMP-9 and ectopic bone formation. Lipid -nucleic acid nanoparticles (LNPs) may be loaded with pBMP-9 for stabilizing bone remodeling during osteoporosis.	Viable cost-effective alternative to rhBMP-9. Resistance to noggin inhibition mimicked by pBMP-9 while driving Smad 1/5/8 phosphorylation. ALP activity reached a steady-state of around 77% after day 1 at around 100 ng/ml. More sustained release of pBMP-9 over rhBMP-9. LNP model of pBMP-9 delivery offers intravenous administration due to its low hemolytic potential.	[124, 126, 127, 147]
Collagen	Nano-hydroxyapatite (nHA)/collagen I (Col type I)/multi-walled carbon nanotube (MWCNT) composite scaffold loaded with rhBMP-9 nHA and MWCNT are nanofillers that facilitate scaffold mechanical properties along with enhancement of bioactivity.	Interconnected porous three-dimensional structure for the scaffold; pore size reduced with an increase in MWCNT amount. Increased MWCNT amount reduced water absorption and scaffold swelling but increased the mechanical strength of the scaffold. Composite structure of the scaffold is a crucial parameter for tuning cellular interaction and subsequent bone regeneration.	Adequate porosity with a uniform pore structure facilitates proper nutrient transport and reduces cell losses. Osteoblast differentiation and subsequent new bone formation were enhanced with a BMP-9 loaded composite scaffold. Enhanced cellular anchorage and cytoskeletal extension in the case of BMP-9 loaded composite scaffolds.	[129]
	Collagen Membrane	Osteoblast behavior is enhanced by the collagen membrane; scaffold biomaterial has significantly more effect on cell attachment and proliferation over the use of BMPs.	Osteopromotive potential increased by coupling porcine collagen membrane with BMP-9, in comparison to BMP-2. A low dosage of BMP-9 (10 ng/ml) also displays promising osteogenic potential.	[141]
	nHA/Col/gelatin microsphere (GM) encapsulated with BMP-9. nHA acts as a nanofiller for enhanced bioactivity.	Interconnected porous structure with nanofiller (nHA) deposition on a collagen matrix. The freeze-drying technique is beneficial in rendering a porous structure to the scaffold. Bone marrow mesenchymal stem cells (BMMSCs) displayed enhanced proliferation in the presence of scaffolds. Increased ALP activity in the scaffold groups from day 4. No pathological changes along with any pyrogenic reactions were observed with the application of the porous scaffold.	Initial cell adhesion (3 h) was enhanced with the presence of scaffold, irrespective of the presence of BMP-9. Scaffold porosity facilitated enhanced cell attachment; cells grew with an elongated morphology. Porous scaffold provided adequate housing for the microsphere encapsulated BMP-9 with an effective release to activate BMMSCs. Biocompatible scaffold with adequate biodegradation with time.	[130]
Methyl Cellulose and Alginate	Methylcellulose/Alginate loaded with Chitosan microparticles coated with BMP-9.	Methylcellulose is thermosensitive and becomes gel at close to physiological temperature. VEGF was added to the gel scaffold to enhance angiogenesis. The presence of BMP-9 in a normal medium in 2D culture displayed enhanced ALP activity.	The blend of methylcellulose (with calcium chloride) with alginate provides adequate crosslinking and mechanical strength to the hydrogel scaffold. Hydrogel scaffold facilitates a much more sustained release profile for microparticle coated BMP-9. BMP-9 in an osteogenic medium enhances ALP activity the most; Alizarin red shows denser and more uniform biomineralization with BMP-9 loaded scaffold. Injectable scaffold.	[139]
Biphasic calcium phosphate	Biphasic calcium phosphate (BCP) particles with BMP-9 adsorption	Micro and macroporous surface of BCP particles. Rough surface of BCP with observed nano topography.	Adequate adsorption of BMP-9 on the biomaterial with sustained release up to day 10. Enhanced osteogenic differentiation with rhBMP-9 loaded BCP scaffold, marked by PCR analysis and Alizarin red staining.	[140]
Fibrinogen and Thrombin	Fibrin Sealant (Brand Name: TISSEEL)	Adequate housing for holding BMPs with a sustained release profile over days 10. Local release of growth factors at the defect site or at the target for bone deposition.	Fibrin sealant is biocompatible, biodegradable with low immunogenicity; safe for in vivo applications. Enhanced osteogenic potential of fibrin sealant with the addition of rhBMP-9, as compared to using fibrin sealant alone.	[142]
Hyaluronic acid (HA)	HA crosslinked with butanediol diglycidyl ether.	HA is an inert biocompatible material. Crosslinked HA revealed a wavy structure with grooves and pits on its surface. 70% of rhBMP-9 could be loaded on to the scaffold with a slow-release profile over 10 days.	Cell growth in a three-dimensional scaffold with HA. HA alone enhances osteocalcin expression on day 14; with the addition of rhBMP-9, the increase in osteogenic differentiation becomes two-fold. Biomineralization, using alizarin red, display a similar trend that highlights the benefit of using HA.	[143]