TNFα siRNA delivery by nanoparticles and photochemical internalization for psoriasis topical therapy

Psoriasis is a chronic inflammatory skin disease that presents increased expression of tumor necrosis factor α (TNFα), a proinflammatory cytokine. The discovery of RNA interference (RNAi), mediated by short interfering RNA (siRNA), made it possible for the expression of some genes to be eliminated. However, for its application, it is necessary to use carriers that can protect siRNA and release it in the target cells. Herein, we developed a delivery system for siRNA based on hybrid polymer-lipid nanoparticles (PLNs) and combined this system with photochemical internalization (PCI), photoactivating the photosensitizer TPPS2a, to optimize the endosomal escape of TNFα siRNA in the cytoplasm, aiming to use the system as a topical formulation to treat psoriasis. The PLNs composed of 2.0% of Compritol® 888 ATO (lipid), 1.5% of poloxamer 188 and 0.1% of the cationic polymer poly(allylamine hydrochloride) showed an average nanoparticle size of 142 nm, a zeta potential of +25 mV, and the ability to efficiently coencapsulate TPPS2a and complexed siRNA. In addition, these materials did not present cellular toxicity and showed high cellular uptake. In vitro delivery studies using porcine skin model revealed that the PLNs delivered siRNA and TPPS2a into the skin. The efficacy was verified using an in vivo psoriasis animal (hairless mouse) model induced by imiquimod (IMQ) cream. The results revealed that PLN-TPPS2a-TNFα siRNA combined with PCI resulted in a decrease in the levels of TNFα, showing the efficiency of the treatment to silence this cytokine in psoriatic lesions, which was accompanied by a reduction in the redness and scaling of the mouse skin. The results showed the potential of the developed PLNs in combined silencing gene therapy and PCI for topical treatment of psoriasis.