Topical delivery of TRPsiRNA-loaded solid lipid nanoparticles confer reduced pain sensation via TRPV1 silencing, in rats

Abstract

Present work describes a novel composition for encapsulating TRPsiRNA (TRPV1-targeting siRNA) within lipid-matrix (4:1::glyceryl behnate:stearic acid) of SLNs, using suitably modified cold high-pressure homogenisation technique. Optimisation of the method and composition conducted using calf-thymus DNA (ctDNA), to avoid cost of TRPsiRNA molecules, resulted in small size (d₅₀ = 50–100 nm) and high entrapment (77.22–98.5%). Complete masking of extreme negative charge of both ctDNA (−34.50 mV) and TRPsiRNA (−23.98 mV) upon encapsulation in SLNs without employing cationic components is reported herein for the first time. Diffusion-controlled release (90.17% at 72 h) from a rigid matrix shifted to porous matrix (at 24 h) due to solubilisation of stearic acid at 37 °C. Efficient in vitro (HEK293 T cells) and in vivo transfection and expression established the proof-of-concept. PEG600 as supporting-surfactant and vitrifying agent promoted small size, effective transfection and rupture of endosomal membrane to affect endosomal escape. Physiological efficacy in terms of significant increase (p < .0001) in paw-withdrawal-latency, following topical and intradermal application of TRPsiRNA-loaded SLNs, in rats, exposed to thermal hyperalgesia (145 and 182%, respectively) and capsaicin-induced pain (155 and 182%, respectively) indicate effective silencing of skin TRPV1. Significant decrease in intensity and duration (one-fifth) of capsaicin-induced nocifensive behaviour was also observed. Naked TRPsiRNA, however, did not show any effect.

Keywords:

• RNA interference
• skin keratinocytes
• transient receptor potential vanilloid-1
• cold high-pressure homogenisation
• nociception
• intradermal
• neuropathic pain
• analgesia

Disclosure statement

All the authors declare that they have no conflict of interest.

Animals ethical clearance

All applicable institutional guidelines for the care and use of animals were followed and the study was approved by Institutional Animal Ethics Committee of Panjab University, Chandigarh, India vide letter number PU/IAEC/5/14/75.

Additional information

Funding

Funding provided by Indian Council of Medical Research, New Delhi (vide letter number: 45/17/2010/NAN-BMS), for this research work is highly acknowledged.