Polymer Membranes Sonocoated and Electrosprayed with Nano-Hydroxyapatite for Periodontal Tissues Regeneration

Abstract

Diseases of periodontal tissues are a considerable clinical problem, connected with inflammatory processes and bone loss. The healing process often requires reconstruction of lost bone in the periodontal area. For that purpose, various membranes are used to prevent ingrowth of epithelium in the tissue defect and enhance bone regeneration. Currently-used membranes are mainly non-resorbable or are derived from animal tissues. Thus, there is an urgent need for non-animal-derived bioresorbable membranes with tuned resorption rates and porosity optimized for the circulation of body nutrients. We demonstrate membranes produced by the electrospinning of biodegradable polymers (PDLLA/PLGA) coated with nanohydroxyapatite (nHA). The nHA coating was made using two methods: sonocoating and electrospraying of nHA suspensions. In a simulated degradation study, for electrosprayed membranes, short-term calcium release was observed, followed by hydrolytic degradation. Sonocoating produced a well-adhering nHA layer with full coverage of the fibers. The layer slowed the polymer degradation and increased the membrane wettability. Due to gradual release of calcium ions the degradation-associated acidity of the polymer was neutralized. The sonocoated membranes exhibited good cellular metabolic activity responses against MG-63 and BJ cells. The collected results suggest their potential use in Guided Tissue Regeneration (GTR) and Guided Bone Regeneration (GBR) periodontal procedures.

Keywords: GTR/GBR membranes; electrospinning; electrospraying; periodontal regeneration; sonocoating.

Figure 1

Electrospinning setup combined with electrospraying.

Figure 2

Schematic view of ultrasonic coating setup and ultrasonic cavitation phenomenon occurring near the membrane surface during the process.

Figure 3

SEM images of PLGA, PDLLA and PDLLA/PLGA samples top view (A–C) and fractured in liquid nitrogen cross-sections (D–F). For each material, fiber diameter histograms are given. Scale bar is 50 μm.

Figure 4

SEM images and morphology scheme of PDLLA/PLGA membrane fibers: (A) Pristine PDLLA/PLGA fiber; (B) fiber electrospray covered with nHA beads; (C) fiber sonocoated with GoHAP 3; (D) fiber sonocoated with GoHAP 6; (E) fiber layer-by-layer sonocoated with GoHAP 6 and GoHAP 3, respectively.

Figure 5

FTIR spectra of a: nHA, PDLLA, PDLLA/PLGA, and PDLLA/PLGA coated with nHA.

Figure 6

XPS spectra of GoHAP 3 and 6 powders compared with natural bone apatite.

Figure 7

XPS spectra of unmodified and nHA double-layer sonocoated materials: (A) PDLLA; (B) PDLLA/PLGA; and (C) PLGA.

Figure 8

TG (A) and DTG (B) curves at heating rate b = 10 °C min⁻¹ of a PDLLA/PLGA (1), PDLLA/PLGA/nHA electrosprayed (2), PDLLA/PLGA/nHA sonocoated, and (3) and nHA (4).

Figure 9

SEM images and water contact angle measurement values of materials and composites: (A–C) PLGA; (D–F) PDLLA; (G–I) PDLLA/PLGA.

Figure 10

Graphs of ICP-OES calcium release and pH changes profiles, and SEM images of PDLLA/PLGA/nHA Electrosprayed fibers, (A–H) PDLLA/PLGA/nHA Sonocoated fibers (I–P), after 2,4,8,10 weeks of degradation (from the top down, respectively).

Figure 11

Graph of molecular weight (Mw) changes in the function of degradation time.

Figure 12

(A) Nominal strain-stress curve for coated and non-coated samples. All graphs show mean and standard deviation (shaded areas) from n = 3. SEM images of samples after tensile tests: (B) PDLLA/PLGA; (C) PDLLA/PLGA/nHA electrosprayed, and (D) PDLLA/PLGA/nHA sonocoated. Optical CCD camera images of (E) PDLLA/PLGA and (F) PDLLA/PLGA/nHA sonocoated during tensile properties testing in PBS.

Figure 13

Metabolic activity of BJ (A) and MG-63 (D) cells seeded on PDLLA/PLGA and PDLLA/PLGA/nHA sonocoated materials after 24 h, 72 h, and 7 days. SEM colorized images of MG-63 cells attachment after 24 h on (B,C) PDLLA/PLGA and (E,F) PDLLA/PLGA/nHA sonocoated materials. (B,E): magnification 10kx; (C,F): magnification 25kx. Metabolic activity expressed as a percentage of the control, mean ± SD from three independent experiments. (*denotes statistically significant difference from unexposed control, p < 0.05).

Figure 14

Scheme of particles release mechanism and SEM images of Electrosprayed (top) and Sonocoated (down) PDLLA/PLGA fibers after 10 weeks of degradation.