Nanocarbons (NCs) are used as biomaterials for preparing drug delivery systems (DDSs), regenerative medicine, and cancer therapy. Nevertheless, the clinical application of NCs remains unclear due to their safety concerns.
Study: Future Prospects for Clinical Applications of Nanocarbons Focusing on Carbon Nanotubes. Image Credit: Vybi/Shutterstock.com
The fundamental techniques became more advanced over the years, facilitating the facile assessment of the NC’s biosafety. Consequently, the optimal controls were established, nanocarbon dispersal techniques were refined, biokinetic evaluation methods were increased, and examinations of carcinogenicity were implemented under stringent conditions.
The present review published in the journal Advanced Science summarizes the contributions made to date on NCs biosafety and applications. This review discussed the latest achievements in evaluation techniques and clarified the scope of carbon nanomaterials in clinical applications.
Nanomaterials in Clinical Applications
For the past 15 years, NCs have been used to create biomaterials. However, NC-based biomaterials for clinical applications remain unavailable due to biosafety concerns. Hence, applying NC biomaterials in clinical settings with current technologies may allow biosafety assessments.
Nanobiomaterials’ biocompatibility and biodegradability are critical for their development. While biocompatibility is an essential characteristic, biodegradability is highly desirable in a few cases. Previous reports discussed non-biodegradable nanomaterials such as nano-sized hydroxyapatite/gold particles, and nanomagnetic compounds. Compared to other nanomaterials, NCs have high biocompatibility and low biodegradability.
For pre-existing bulk biomaterial complexes and local implantation, NCs are incorporated into the bulk materials to improve therapeutic efficiency in existing biomaterials. For example, combining polyethylene with NCs reinforced the polymer to reduce wear. Similarly, complexing the collagen with NCs enhanced bone restoration, as reported previously.
Incorporating multi-walled carbon nanotubes (MWCNTs) into collagen promotes in vitro osteoblast proliferation. The MWCNTs reinforced collagen composite was intramuscularly implanted as collagen composite for recombinant human bone morphogenetic protein-2 (rhBMP-2) in lab animals, where MWCNTs served as a DDS and were bound to the bone tissue and incorporated into the bone.
Previous reports mentioned that MWCNT-based collagen composites had no inflammation in the muscle, causing little biological responses to the external substance. MWCNT-reinforced collagen promoted greater bone formation than collagen alone and prevented adverse effects like osteolysis due to good bone tissue affinity.
The induction of tumors in different organs is the most critical issue in confirming the biosafety of NCs. The previous reports confirmed that administering NCs into the circulatory system did not induce tumor formation in laboratory animals. However, the inhalation of NCs caused carcinogenicity. Moreover, CNTs were previously reported to induce tumors on intraperitoneal administration in laboratory animals.
CNTs in Clinical Applications
Ultrahigh molecular weight polyethylene (UHMWPE) wears quickly when used alone in artificial joint sliding elements. Moreover, crosslinked UHMWPE used in total hip arthroplasty (THA) has low impact resistance and breaks easily. Thus, using crosslinked UHMWPE is not recommended for total knee arthroplasty (TKA).
To this end, UHMWPE complexed with MWCNTs were evaluated for their safety in artificial joints. The results revealed that the wear resistance of MWCNT/UHMWPE composites was like that of crosslinked UHMWPE and the impact resistance showed a similar trend as in non-crosslinked UHMWPE. The MWCNT/UHMWPE composites met all the required criteria for their application in an implantable medical device, per the international organization for standardization (ISO) 10993 series.
Considering the possibility of MWCNT presence in wear debris, it was injected into the knee joint of a rat, followed by monitoring the progress for 26 weeks. The results revealed a very mild inflammation in the joint which quickly became passive. Furthermore, no migration of MWCNTs was observed to any other organ. Thus, MWCNT/UHMWPE composites were confirmed to be new biomaterial with clinical safety, high wear resistance, and impact resilience for their application in treating both THA and TKA.
Conclusion and Scope
The clinical potential of NCs was summarized in the present article. Currently, the interests of researchers lie in identifying the optimal control, evaluating the dispersal techniques of NC, selecting the biokinetic evaluation methods, and testing carcinogenicity under extreme conditions. Since the basic techniques for NC’s biosafety assessment have become sophisticated, there is a need for new preparations for their clinical applications.
NCs-based pre-existing bulk biomaterials are of first preference for clinical applications, followed by NC particles for local treatment of lethal diseases like cancer. Although these materials could reap incredible benefits, their application may need some encouragement from patient candidates.
Additionally, the social perception of NCs has changed favorably, and indisputable evidence has proved their tolerance and safety. Although the consequence of administering NCs into the circulatory system remains unclear at present, consistent advancements in research could overcome this impediment. Thus, the cumulative research contribution toward NC biomaterial research and development could bring a paradigm shift and advancements in global medicine and clinical applications.
Saito, N., Haniu, H., Aoki, K., Nishimura, N., Uemura, T (2022) Future Prospects for Clinical Applications of Nanocarbons Focusing on Carbon Nanotubes. Advanced Science. https://doi.org/10.1002/advs.202201214
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