Evidence for Contamination of Silica Microparticles in Advanced Platelet-Rich Fibrin Matrices Prepared Using Silica-Coated Plastic Tubes

Abstract

Platelet-rich fibrin (PRF) therapy has been widely applied in regenerative dentistry, and PRF preparation has been optimized to efficiently form fibrin clots using plain glass tubes. Currently, a shortage of commercially available glass tubes has forced PRF users to utilize silica-coated plastic tubes. However, most plastic tubes are approved by regulatory authorities only for diagnostic use and remain to be approved for PRF therapy. To clarify this issue, we quantified silica microparticles incorporated into the PRF matrix. Blood samples were collected into three different brands of silica-containing plastic tubes and were immediately centrifuged following the protocol for advanced-PRF (A-PRF). Advanced-PRF-like matrices were examined using a scanning electron microscope (SEM), and silica microparticles were quantified using a spectrophotometer. Each brand used silica microparticles of specific size and appearance. Regardless of tube brands and individual donors, significant, but not accidental, levels of silica microparticles were found to be incorporated into the A-PRF-like matrix, which will be consequently incorporated into the implantation sites. Presently, from the increasing data for cytotoxicity of amorphous silica, we cannot exclude the possibility that such A-PRF-like matrices negatively influence tissue regeneration through induction of inflammation. Further investigation should be performed to clarify such potential risks.

Acute cytotoxic effects of silica microparticles used for coating of plastic blood-collection tubes on human periosteal cells

“…In comparison with the negative control, Cytrans Granules, silica microparticles derived from Neotube and Vacuette significantly reduced cell viability at the dilution of 1:32 and 1:16, respectively. Since Venoject II contains fewer silica microparticles per tube [2], its silica particles exerted growth inhibitory effects at lower dilutions (1:4 and lower). However, when not diluted, all the silica microparticles substantially inhibited growth.…”

“…Based on the previous findings [2], the sizes of silica microparticles in individual tubes are roughly determined. Neotube: several microns to 40 μm, Vacuette: submicrons to 20 μm, Venoject II: submicrons to 6 μm.…”

“…Periosteal cells were seeded at a density of 8 × 10 4 cells in a 35 mm-diameter dish and incubated with silica microparticles diluted 1:8 for 1-3 days, fixed with 2.5% neutralized glutaraldehyde, dehydrated, and freeze-dried as described previously [2,15]. The rim of the dish was removed and examined by SEM) using a TM-1000 microscope (Hitachi, Tokyo, Japan) at an accelerating voltage of 15 kV.…”

“…PRF preparation requires only a plain glass tube to activate the intrinsic coagulation pathway to form a fibrin clot [1]. However, this simple prerequisite has ironically proven problematic in the clinical setting, since the production of plain glass tubes has been discontinued by major medical device manufacturers, restricting a stable supply of the tubes for clinicians [2,3]. Instead, based on information from local distributors and/or other clinicians, they tend to use silica-coated plastic blood collection tubes, as the tubes are produced by major manufacturers and are readily available.…”

“…The use of the tubes for PRF therapy can be questioned. To address this concern, in a previous study [2], we demonstrated using spectrophotometric and microscopic methods that silica microparticles detached from the inner wall are immediately incorporated into the PRF matrix.…”