Nitric Oxide Dependent Degradation of Polyethylene Glycol-Modified Single-Walled Carbon Nanotubes: Implications for Intra-Articular Delivery

Abstract

Polyethylene glycol (PEG)-modified carbon nanotubes have been successfully employed for intra-articular delivery in mice without systemic or local toxicity. However, the fate of the delivery system itself remains to be understood. In this study 2 kDa PEG-modified single-walled carbon nanotubes (PNTs) are synthesized, and trafficking and degradation following intra-articular injection into the knee-joint of healthy mice are studied. Using confocal Raman microspectroscopy, PNTs can be imaged in the knee-joint and are found to either egress from the synovial cavity or undergo biodegradation over a period of 3 weeks. Raman analysis discloses that PNTs are oxidatively degraded mainly in the chondrocyte-rich cartilage and meniscus regions while PNTs can also be detected in the synovial membrane regions, where macrophages can be found. Furthermore, using murine chondrocyte (ATDC-5) and macrophage (RAW264.7) cell lines, biodegradation of PNTs in activated, nitric oxide (NO)-producing chondrocytes, which is blocked upon pharmacological inhibition of inducible nitric oxide synthase (iNOS), can be shown. Biodegradation of PNTs in macrophages is also noted, but after a longer period of incubation. Finally, cell-free degradation of PNTs upon incubation with the peroxynitrite-generating compound, SIN-1 is demonstrated. The present study paves the way for the use of PNTs as delivery systems in the treatment of diseases of the joint.

Polyethylene glycol modified carbon nanotubes (PNTs) are injected intra-articularly into the knee-joint of C57BL/6 mice and their fate is monitored by using Raman spectroscopy–microscopy. Degradation of PNTs is documented mainly in the chondrocyte-rich cartilage region. Subsequent in vitro experiments confirm nitric oxide-dependent degradation of PNTs in activated murine chondrocytes as well as cell-free, peroxynitrite-mediated degradation of PNTs.

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