Combinatorial design of calcium meta phosphate poly(vinyl alcohol) bone-like biocomposites

Abstract

The incidence of degenerative diseases and the ageing population have added to the growing demand for bone grafts. Although autologous bone continues to be the gold standard, limited yield and potential morbidity of the donor site pose considerable challenges. Currently, clinically used synthetic grafts based on calcium phosphates are mechanically brittle and not compliant hence composite scaffolds are expected to be provide viable solutions. In this study we report composites of calcium meta phosphate-poly (vinyl alcohol) with tunable mechanical properties, low swelling and excellent biocompatibility. The elastomeric nature of the composites resist brittle fracture and the scaffolds can be easily shaped to the bone defect by the surgeon. Testing on bone plug shaped specimens of the scaffolds, exhibited superior mechanical properties compared to currently commercially available bone plugs with additional advantages being the ability to increase porosity without compromising properties in compression and degree of swelling, which make these composites promising synthetic alternatives for bone grafts and bone tissue engineering.

Dual Network Composites of Poly(vinyl alcohol)-Calcium Metaphosphate/Alginate with Osteogenic Ions for Bone Tissue Engineering in Oral and Maxillofacial Surgery

“…The broad peak centred at 3300 cm −1 arises from -OH stretching vibrations of PVA and alginates, whilst peaks around 2835–2940 cm −1 were attributed to the C-H stretching of PVA alkyl groups [ 20 ], the peak at 1650 cm −1 is due to C=O stretching of PVA acetate group [ 21 ], and the peak at 1310 cm −1 corresponds to -C-H and -OH vibration of PVA [ 21 ]. Overlapping peaks in the fingerprint region were attributed to (i) C-H wagging and twisting of PVA alkyl groups (1100–1250 cm −1 ), (ii) C-O vibrations of PVA hydrogen bonds (1115 cm −1 ) and (iii) P-O vibrations of the CMP phosphate groups (650–1200 cm −1 ) [ 13 ]. The presence of alginate also manifests in: (i) stretching of C-H anomer (2835–2940 cm −1 ); asymmetric and symmetric stretching of COO − (1590–1605 cm −1 and 1410–1420 cm −1 ); bending of C-C-H and O-C-H (1305–1310 cm −1 ); C-O stretching (1120–1150, 1025–1030 and 935–950 cm −1 ); O-C-O ring shoulder (1060–1090 cm −1 ); C-H bending of mannuronate (800–890 cm −1 ) and guluronate (780 cm −1 ) [ 22 ].…”

“…The low EWC of DNCs is favoured as extreme swelling can compromise the scaffold mechanical properties and likely exert pressure to surrounding tissues, which can hinder vascularisation and provoke tissue necrosis [ 13 ]. Despite the higher swelling of DNCs compared to the SNC, which can be attributed to the presence of a second highly hydrophilic network, DNC compressive properties were maintained ( Figure 2 ) due to its denser network.…”

“…CMP was prepared by admixing CPMM and PVA in 4:1 weight ratio and heated in furnace as described earlier [ 13 , 17 ] and ground to particles with an average particle size diameter of ±14 µm. The SNC of PVA-CMP was fabricated as described by Nkhwa et al [ 13 ].…”

“…CMP was prepared by admixing CPMM and PVA in 4:1 weight ratio and heated in furnace as described earlier [ 13 , 17 ] and ground to particles with an average particle size diameter of ±14 µm. The SNC of PVA-CMP was fabricated as described by Nkhwa et al [ 13 ]. In brief, a 10% ( w/v ) PVA solution and a slurry with CMP prepared at a ratio of PVA/CMP = 40/60 and 10% gelatine granules as porogen was subjected to two freeze–thawing cycles (2FT).…”

“…The DN’s were formed using water-soluble polymers of poly(vinyl alcohol) (PVA) and alginate crosslinked via freeze–thawing (FT) of PVA and calcium salt solution chelation without incorporation of toxic solvents, initiators, activators and crosslinking agents. Combining the principle of forming DNs and our previous work on SBS based on single network composites (SNC) of poly(vinyl alcohol) (PVA) and calcium metaphosphate (CMP) [ 13 ], dual network composites (DNC) were designed to enhance clinical viability. The first network of the PVA-alginate DN was formed by FT of PVA solution and subsequently swollen in sodium alginate solution chelated with calcium chloride to form the second network.…”