Beneficial effect of hydrophilized porous polymer scaffolds in tissue‐engineered cartilage formation

Abstract

Three dimensional (3D) porous poly(L-lactic acid) (PLLA) scaffolds were fabricated using a modified gas foaming method whose effervescent porogens were a mixture of sodium bicarbonate and citric acid. To improve chondrocyte adhesion, the scaffolds were then hydrophilized through oxygen plasma treatment and in situ graft polymerization of acrylic acid (AA). When the physical properties of AA-grafted scaffolds were examined, the porosity and pore size were 87 approximately 93% and 100 approximately 300 microm, respectively. The pore sizes were highly dependent on the varying ratios (w/w) between porogen and polymer solution. Influenced by their pore sizes, the compressive moduli of scaffolds significantly decreased with increasing pore size. The altered surface characteristics were clearly reflected in the reduced water contact angles that meant a significant hydrophilization with the modified polymer surface. Electron spectroscopy for chemical analysis (ESCA) and time-of-flight secondary ion mass spectrometer (ToF-SIMS) also confirmed the altered surface chemistry. When chondrocytes were seeded onto the AA-grafted PLLA scaffolds, cell adhesion and proliferation were substantially improved as compared to the unmodified scaffolds. The benefit of the modified scaffolds was clear in the gene expressions of collagen type II that was significantly upregulated after 4-week culture. Safranin-O staining also identified greater glycosaminoglycan (GAG) deposition in the modified scaffold. The AA-grafted porous polymer scaffolds were effective for cell adhesion and differentiation, making them a suitable platform for tissue-engineered cartilage.

Chitosan-based scaffolds for bone tissue engineering

“…70 Gas bubbles form by either (1) mixing a foaming or blowing agent, such as sodium bicarbonate, with a pre-polymer where gas is generated upon chemical decomposition 76, 77 or (2) saturating a polymer with subcritical or supercritical gas at high pressure where depressurization results in thermodynamic instability leading to nucleation, growth and coalescence of gas bubbles as illustrated in Figure 3c. 78, 79 Gas foaming does not necessitate the use of organic solvents, but pore formation and porosity depend on rate of nucleation and gas diffusion, which can be difficult to control.…”

Plasma Surface Modification of Biodegradable Polymers: A Review

“…However, the authors did not examine the effect of these plasma‐polymerized heptylamine coatings on cell adhesion and proliferation. Besides allylamine and heptylamine, also acrylic acid has been plasma‐polymerized on the surface of biodegradable polyesters 154–156. This plasma polymerization method creates hydrophilic surfaces containing a high amount of COOH groups, which can significantly enhance cell attachment and proliferation 154, 155…”

Scaffold structure and fabrication method affect proinflammatory milieu in three‐dimensional‐cultured chondrocytes

“…Such mechanical property could be related to the water‐uptake ability or swelling ratio of the scaffolds, which is indicative of hydrophilicity . The previous studies have shown that hydrophilic scaffolds supported better cartilage formation through enhanced collagen type II expression and cell redifferentiation in chondrocytes . It is possible that higher hydrophilicity allows for optimal function of the ECM, and thus higher levels of matrix production.…”