Platelet Use in Reducing Rejection Rates
Platelets are cell fragments surrounded by membranes, and their main function is to act with fibrin to stop blood flow in wounds. These fragments also carry special proteins that render them invisible to the immune system. Taking advantage of this, Chinese researchers developed a method to apply these membranes to implant devices, such as vascular stents.1 Their goal is to prevent the immune system from recognizing implanted devices as foreign bodies.
Current uses for this technology include protecting proteins and nucleic acids, disguising nanoparticles employed for drug delivery, and extending drug circulation time.2 Reporting in Matter, the Chinese team discovered that platelet membranes also spread easily over superhydrophilic surfaces.1 But metallic structures do not have the negative charge needed to make platelets adhere, so the investigators covered test surfaces with a solution of dopamine and sodium periodate. This allowed application of a negative charge so platelets could completely cover the device.
Once sufficient coverage was achieved, they tested the coating on the types of stents placed into clogged arteries by cardiovascular surgeons to keep the blood vessels patent. Currently available stents often stimulate an immune response, which can cause scarring. In some cases, this scar tissue breaks loose and can result in stroke or pulmonary embolism. To assess the efficacy of the coating, researchers placed the platelet-covered stents into the abdominal aortas of rabbits. Stents with no coating or with only a polydopamine coating served as controls.
One group of stents was removed after eight hours and evaluated for a buildup of inflammatory cells. Others were left in place for 30 days before sacrifice and evaluation. The eight-hour control stents were already covered with cells stimulated by an immune response, while the coated test stents were clean. In the specimens evaluated at 30 days, the control stents showed cell covering that indicated scarring, while the test stents had no adhering cells.
Although potential applications for this technology are promising, these results were in non-humans and the stents remained in place for only short periods. A great deal of study is needed before longevity and application to humans can be ascertained. But, if successful, this technology would have widespread applications in medicine.
For example, the use of this (or similar) technology in dental implants is certainly appealing; however, the environments in which these two devices exist are radically different. Cardiovascular stents are used in a closed environment, whereas dental implants are constantly bathed in the bacterial soup of the oral cavity. Despite these challenges, it is hoped this new coating technology might make dental implants more resistant to bacterial attack and corrosion, thus improving long-term implant success.
Thomas G. Wilson Jr., DDS
Editor in Chief
- Zhou Z, Luo R, Chen L, et al. Dressing blood-contacting devices with platelet membrane enables large-scale multifunctional biointerfacing. Matter. 2022;5:2334–2351.
- Han H, Bártolo R, Li J, Ali Shahbazi M, Santos HA. Biomimetic platelet membrane-coated nanoparticles for targeted therapy. Eur J Pharm Biopharm. 2022;172:1–15.
From Decisions in Dentistry. September 2022;8(9)4.