Effect of Porous Activated Charcoal Reinforcement on Mechanical and In-Vitro Biological Properties of Polyvinyl Alcohol Composite Scaffolds

doi:10.1016/j.jmst.2016.06.020

Abstract

Abstract:

The present work focused on developing an innovative composite material by reinforcing polymer matrix with highly porous activated charcoal. Polyvinyl alcohol-activated charcoal (PVA-AC) composite scaffolds were developed by varying the AC concentrations (0, 0.5, 1, 1.5, 2 and 2.5 wt%) in PVA matrix by freeze drying method. The developed scaffolds were characterized for their physicochemical, mechanical and in-vitro biological properties. In addition, the effect of AC on the attachment, proliferation and differentiation of osteoblast MG 63 cells was evaluated by scanning electron microscopy (SEM), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, alkaline phosphatase (ALP) activity assay and alizarin red stain-based (ARS) assay. All the PVA-AC composite scaffolds exhibited good bioactivity, hemocompatibility and protein adsorption properties. The scaffolds with high AC concentration (2.5 wt%) showed controlled drug release kinetics that are suitable for long term healing. The mechanical properties of all the PVA-AC composite scaffolds were improved when compared to the pure PVA scaffold. The high porosity, swelling degree and hydrophilicity of PVA-AC composite scaffolds facilitated cell attachment and proliferation. This is due to porous AC present in the sample that supported the osteoblast differentiation and formed mineralized nodules without the addition of any extra agents. From the above studies, it can be concluded that PVA-AC composite scaffolds are promising biomaterials for bone tissue engineering applications.

Key words: Polyvinyl alcohol, Activated charcoal, Porous reinforcement, Bioactivity, Mechanical studies, Osteoblast proliferation and differentiation

Kaur Tejinder, Thirugnanam Arunachalam. Effect of Porous Activated Charcoal Reinforcement on Mechanical and In-Vitro Biological Properties of Polyvinyl Alcohol Composite Scaffolds[J]. J. Mater. Sci. Technol., 2017, 33(7): 734-743.

Figures/Tables 14

Fig. 1. Schematic representation of PVA-AC composite scaffold preparation.

Fig. 2. (a) FESEM micrographs of PVA and various PVA-AC composite scaffolds (arrows show the shrinkage and collapse of the pores in PC 0 sample), (b) high magnification micrographs of PC 2.5 with arrows showing dispersed AC in PVA matrix, (c) average pore size of the scaffolds.

Table 1 Average pore diameter and average pore volume of PVA-AC composites obtained from MIP

Sample	Average pore diameter (μm)	Average pore volume (%)
PC 0	22.4 ± 2.2	66.2 ± 5.2
PC 0.5	34.8 ± 2.4	72.5 ± 3.6
PC 1	43.8 ± 3.7	75.2 ± 8.4
PC 1.5	48.6 ± 6.5	76.9 ± 5.4
PC 2	55.8 ± 4.9	79.5 ± 7.1
PC 2.5	68.6 ± 6.3	80.6 ± 6.3

Fig. 3. (a) XRD pattern and (b) FTIR spectrum of the AC and processed PVA-AC composite scaffolds.

Fig. 4. DSC curves for the processed PVA-AC composite scaffolds.

Table 2 Average contact angles of PVA-AC composites

Sample	Average contact angle (deg.)
PC 0	51.04 ± 2.5
PC 0.5	47.28 ± 1.34
PC 1	45.34 ± 5.27
PC 1.5	45.06 ± 0.56
PC 2	44.8 ± 1.64
PC 2.5	43.56 ± 1.63

Fig. 5. Percentage porosity measurements of PVA-AC composite scaffolds.

Fig. 6. Swelling studies of the processed PVA-AC composite scaffolds in PBS.

Fig. 7. SEM micrographs of (a) PC 0, (b) PC 0.5, (c) PC 1, (d) PC 1.5, (e) PC 2, (f) PC 2.5, and (g) XRD pattern of in-vitro bioactivity studies of PVA-AC composite scaffolds in SBF.

Table 3 Hemolysis (%) of PVA-AC composites

Sample	Hemolysis (%)
+ve control	100
-ve control	0
PC 0	0.26 ± 0.15
PC 0.5	0.14 ± 0.10
PC 1	0.29 ± 0.10
PC 1.5	0.18 ± 0.05
PC 2	0.11 ± 0.05
PC 2.5	0.22 ± 0.10

Fig. 8. Amount of protein adsorbed by PVA-AC composite scaffolds.

Fig. 9. Cumulative percentage of in-vitro drug release of TCH from PVA-AC composite scaffolds.

Table 4 Mechanical properties of PVA-AC composites

Sample	Tensile strength (MPa)	Young's modulus (MPa)	Extension at break (mm)	Percentage elongation (%)	Energy at break (mJ)
PC 0	0.72 ± 0.09	24.85 ± 1.13	4.52 ± 0.20	30.13 ± 1.60	17.31 ± 1.07
PC 0.5	1.00 ± 0.15	29.32 ± 6.10	4.94 ± 0.29	32.93 ± 1.93	24.80 ± 2.00
PC 1	1.39 ± 0.26	42.71 ± 2.12	6.92 ± 0.56	46.13 ± 3.73	50.21 ± 4.76
PC 1.5	1.45 ± 0.11	43.04 ± 6.00	6.09 ± 0.34	40.60 ± 2.99	51.90 ± 5.29
PC 2	1.68 ± 0.19	52.57 ± 10.52	5.96 ± 0.44	39.73 ± 2.81	40.84 ± 2.65
PC 2.5	2.21 ± 0.25	111.57 ± 15.91	3.10 ± 0.10	20.66 ± 0.70	44.64 ± 2.45

Fig. 10. (a) Percentage cell viability, (b) FESEM micrographs, (c) relative ALP activity and (d) relative mineralization of PVA-AC composites cultured with MG 63 cells. Arrows indicate secreted matrix on composite samples by osteoblast cells.

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