Nanodiamond-chitosan functionalized hernia mesh for biocompatibility and antimicrobial activity

Abdominal wall hernia is the result of abdominal wall muscle or connective tissue weakness that allows visceral organs to herniate through. Several prosthetic biomaterial-based devices for hernia repair are available, while more innovative and clinically efficient ones are under investigation. Among them, polypropylene meshes have been accepted for a long time as a standard element for abdominal hernia repair. These meshes are pliable, well incorporable into adjacent tissues and capable of giving robust mechanical support. However, poor flexibility, adhesion to visceral organs and inflammatory risks are problems connected with the utilization of these materials. Besides, the mesh is inert and hydrophobic, with poor cell attachment and proliferation. Ideally, the implantable mesh should trigger a minimum immune response and exhibit excellent biocompatibility to accelerate the healing process for proper integration into the body. This is why decorating the polypropylene mesh with bio-friendly materials to enhance its biocompatibility is highly desired.

Since the use of metal nanoparticles in biological settings is limited, an alternative to decorate the implantable mesh is the use of copolymers and composites. Unfortunately, the process is cumbersome, and the materials developed are structurally complex. Another alternative is the use of bioactive materials. One example of these materials is chitosan, which exhibits excellent biocompatibility, biodegradability, nontoxicity, and antimicrobial properties.

Various crosslinkers, including formaldehyde, glyoxal and citric acid, are used to enhance the attachment of chitosan to the surface of polypropylene mesh. However, some of these crosslinkers are toxic and exhibit poor interaction with cells. Therefore, oxygen plasma treatment has been fronted as a suitable option to activate the polypropylene mesh surface to improve chitosan attachment.

Since chitosan’s antifungal and antimicrobial properties depend on various factors such as pH, molecular weight, and the microorganism cell wall properties, its sole use might be insufficient. Incorporating an active substance to improve its microbial activity is still needed. Detonation nanodiamond is an excellent example of carbon-based nanoparticles with low toxicity and multiple functional groups allowing further surface functionalization in several applications.

The application of nanodiamond and chitosan has been reported in the literature. However, the application of chitosan and hydroxylated nanodiamond composites on polypropylene mesh hasn’t been investigated for microbial and cellular activities.

Given this, Australian researchers from RMIT University: Tanushree Saha, Dr. Shadi Houshyar, Dr Satya Ranjan Sarker, Dr. Suneela Pyreddy, Dr. Chaitali Dekiwadia, Dr. Zeyad Nasa, Professor Rajiv Padhye, and Dr. Xin Wang developed a new innovative method for the designing of an antimicrobial and biocompatible polypropylene mesh via modification with bioactive chitosan and functionalized nanodiamond to accelerate the healing process after surgery and inhibit infection. Their research work has been published in the Journal of Biomedical Materials Research.

The research team used an oxygen plasma-treated polypropylene mesh and attached chitosan to its fibers. Subsequently, they loaded functionalized nanodiamonds into the chitosan-modified polypropylene fiber to provide the much-needed antibacterial properties. The authors characterized the meshes with various advanced analytical tools such as optical microscopy, XRD, water angel contact, FTIR, and SEM.

Coated-cured polypropylene mesh led to optimal chitosan attachment to the polypropylene mesh surface and a longer time in vitro. When the authors treated the chitosan-coated polypropylene mesh with a low concentration (0.3%) of functionalized nanodiamond, the cell attachment was significantly enhanced (i.e., 134%).

The authors observed that the modified polypropylene mesh with chitosan and functionalized nanodiamond exhibited superb resistance to E. coli bacteria besides having excellent fibroblast cell proliferation ability and biocompatibility. Moreover, the researchers recorded a negative effect on cell attachment in vitro when they used citric acid as a crosslinker to improve chitosan attachment to the plasma-treated polypropylene surface. From the surface characterization results of this novel polypropylene mesh modified with chitosan and functionalized nanodiamond, the authors concluded that it’s possible to adopt this new strategy to develop an efficient interactive PP hernia mesh.

The excellent performance of the newly developed by RMIT scientists of functionalized nanodiamond-treated polypropylene mesh opens new avenues for further drug loading by functionalized nanodiamonds in resolving long-standing post-operational complications and therapy.