Electrospun Bioresorbable Membrane Eluting Chlorhexidine for Dental Implants

Abstract

To prevent the uncontrolled development of a pathogenic biofilm around a dental implant, an antimicrobial drug-release electrospun membrane, set up between the implant and the gingival tissue, was developed by taking several technical, industrial and regulatory specifications into account. The membrane formulation is made of a blend of poly(l-lactic-co-gycolic acid) (PLGA, 85:15) and poly(l-lactic acide-co-ɛ-caprolactone) (PLC, 70:30) copolymers with chlorhexidine diacetate (CHX) complexed with β-cyclodextrin (CD). The amount of residual solvent, the mechanical properties and the drug release kinetics were tuned by the copolymers' ratio, between 30% and 100% of PLC, and a CHX loading up to 20% w/w. The membranes were sterilized by γ-irradiation without significant property changes. The fiber's diameter was between 600 nm and 3 µm, depending on the membrane composition and the electrospinning parameters. CHX was released in vitro over 10 days and the bacterial inhibitory concentration, 80 µg·mL^-1, was reached within eight days. The optimal membrane, PGLA/PLC/CHX-CD (60%/40%/4%), exhibited a breaking strain of 50%, allowing its safe handling. This membrane and a membrane without CHX-CD were implanted subcutaneous in a rat model. The cell penetration remained low. The next step will be to increase the porosity of the membrane to improve the dynamic cell penetration and tissue remodeling.

Keywords: bioresorbable polymers; dental membrane; drug delivery; electrospinning; peri-implantitis.

Figure 1

Fourier-transform infrared spectroscopy (FTIR) spectrum of the CHX, CD, the complex CHX-CD, the membrane PLGA/PLC: (60:40), the membrane PLGA/PLC/CHX (60:40:4) and the membrane PLGA/PLC/CHX-CD (60:40:4).

Figure 2

Cumulative CHX release (%) through time according to the complexation of CHX with CD and polymers′ concentrations, as measured by UV spectrometry. The formulation used was PLGA:PLC (60/40) with CHX (4%). CHX + CD means CHX and CD were added together during the polymers′ solubilization. The lyophilized CHX-CD complex powder was added during the polymers′ solubilization.

Figure 3

SEM images of fibers according to their formulations. Mean fiber diameter: (A) 1458 ± 174 nm; (B) 2996 ± 189 nm; (C) 655 ± 366 nm; (D) 642 ± 270 nm; (E) 824 ± 362 nm; (F) 746 ± 297 nm. In (A), fibers were electrospun with a 0.4 mm capillary. In (D), the lyophilized CHX-CD complex powder was added into the polymers solution.

Figure 4

DSC curves of the PLGA/PLC/CHX (60:40:4) membranes before and after sterilization with gamma irradiation or EtO treatment. The two graphics show the results after the first heating cycle (top) and the second heating step (bottom).

Figure 5

Cumulative CHX release according to the CHX loading with the formulation PLGA/PLC/CHX-CD (60:40) before and after sterilization by γ-irradiation, measured by UV spectrometry.

Figure 6

Cumulative CHX release according to the PLGA/PLC ratio. CHX-CD loading was 4%, measured by UV spectrometry.

Figure 7

Cumulative CHX release according to the CHX-CD loading with the formulation PLGA/PLC (60:40), measured by UV spectrometry.

Figure 8

Daily CHX concentration, measured by UV spectrometry, released by a membrane (115 mm³) according to the formulation (polymer ratio and CHX loading).

Figure 9

Stress–strain curve according to the ratio between PLGA and PLC copolymers for a CHX loading of 4%.

Figure 10

Strain at break according to the loading of CHX before and after sterilization (p = 0.118) for PLGA/PLC (60:40) membrane.

Figure 11

Semi-quantitative histopathologic analysis table (n = number of membranes analyzed, mean ± SD) after 20 days of sub-cutaneous implantation and photomicrographs of the implanted membranes. Legend: allow arrows: no local tissue integration, bracket: extend of cells tissue ingrowth, black arrows: neovessels, grey arrow: active fibroblasts, M: membrane, FC: Fibrous encapsulation. * One sample was damaged during the technical preparation.