Enhanced Cartilage Regeneration: Chemical, Mechanical, and In Vitro Analysis of Innovative TiO2-Reinforced PVA Implants

Abstract

This study focuses on developing a synthetic, biocompatible graft for treating cartilage lesions. One-dimensional titanium dioxide nanotubes (TNTs) were incorporated into poly(vinyl alcohol) (PVA) hydrogel and processed using freeze-drying without chemical surfactants. Upon optimization of the composition, it was found that the incorporation of TNT altered the biomechanical properties without causing any adverse physiological effects. Annealing treatment further enhanced mechanical strength and energy dissipation, promoting elasticity. The hydrogel with 2 wt % TNT achieved maximum mechanical strength and the storage modulus values indicated elastic dominance, and biotribological tests showed cartilage-like frictional response via hydrodynamic lubrication. Against the microorganisms Escherichia coli, Staphylococcus aureus, and Candida albicans, grafts showed significant antimicrobial activity. In vitro experiments demonstrated that these nanocomposite hydrogels supported adhesion, proliferation, and upregulation of cartilage-specific gene expression in human mesenchymal stem cells hMSCs. This suggests potential for promoting hMSC chondrogenic differentiation and accelerating cartilage regeneration.

Figure 1

illustrates titanium dioxide nanotubes: (a) SEM image and (b) TEM image.

Figure 2

SEM images of hydrogels (a) PVA, (b) PVA/1.5TNT, (c) PVA/2TNT, and (d) PVA/3TNT.

Figure 3

illustrates the FTIR spectrum of TNT, PVA, and the PVA/TNT composite hydrogel.

Figure 4

Schematic representation of electrostatic interaction and hydrogen bond formation between PVA and TNT in the composite hydrogel

Figure 5

illustrates the tensile stress–strain curves of both PVA and its composite hydrogel.

Figure 6

Illustrates the compression stress–strain curve of the composite hydrogel.

Figure 7

Displays the cyclic loading and unloading compression curves for the PVA/2TNT composite hydrogel at strain rates ranging from 10 to 40 mm/min.

Figure 8

Compressive stress–strain curve of the PVA/2TNT composite hydrogel after 1000 loading–unloading cycles.

Figure 9

Illustrates the variation of the storage modulus (G′) and loss modulus (G″) as a function of angular frequency.

Figure 10

illustrates the variation in the friction coefficient of PVA and PVA/TNT hydrogels over time.

Figure 11

Antibiogram of PVA and its composite hydrogel against E. coli, S. aureus bacteria, and C. albicans fungi after 12 h of culture.

Figure 12

hMSCs cell viability on PVA and PVA/2TNT composite hydrogel after 24, 48, and 72 h of culture.

Figure 13

Cell viability assay for PVA/2TNT constructs using live/dead fluorescent staining after 72 h of culture. Live stem cells are stained green, while dead cells are stained red.

Figure 14

(a) Viability of hMSCs on PVA/2TNT hydrogel on day 0, (b) differentiation of hMSCs into mature osteoblasts on day 21, and (c) ALP activity in neat PVA and composite hydrogels.

Figure 15

Inverted microscope images showing chondrocyte differentiation from hMSCs after 21 days of culture.

Figure 16

(a) Viability of chondrocytes on the hydrogel surface after 21 days of hMSC culture and (b) RT-PCR results depicting EXT-2 gene expression following 21 days of cell culture.