Co-delivery of luteolin and TGF-β1 plasmids with ROS-responsive virus-inspired nanoparticles for microenvironment regulation and chemo-gene therapy of intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is closely related to inflammation and imbalance of synthesis/catabolism of extracellular matrix (ECM) in intervertebral disc (IVD). Considering this, luteolin (LUT), a kind of natural flavonoid with good anti-inflammatory effect and TGF-β1 (a gene that promotes the regeneration of ECM) plasmid was co-loaded and co-delivered to nucleus pulposus cells (NPCs). Reactive oxygen species (ROS) responsive cationic copolymer, poly(β-amino ester)-poly(ε-caprolactone) (PBC), with high plasmid DNA (pDNA) compression affinity was synthesized. It can self-assemble into nano-sized polyplexes (pDNA@PBC) with virus-inspired structure and function through which it can transfect pDNA into NPCs with very high efficiency and negligible cytotoxicity. LUT was encapsulated in the hydrophobic core of pDNA@PBC. The co-delivery system, LUT-pTGF-β1@PBC, could enhance the cellular uptake of NPCs and manifest excellent sustained drug release in IVD. Real time quantitative polymerase chain reaction (RT-qPCR) and Western blot experiments reveal that the co-delivery system could inhibit inflammation in NPCs and restore the balance of anabolism and catabolism in vitro by activating TGF/SMAD3 and inhibiting NF-kB/p65. Moreover, LUT-pTGF-β1@PBC retards IDD in vivo as detected by radiological and histological methods with good biosafety in rats. LUT-pTGF-β1@PBC may be a promising option for the treatment of IDD.