Effective Therapy Of Pimecrolimus Polymeric Micelles And Thermoresponsive Nano-hydrogel In A Mouse Model Of Keratoconjunctivitis Sicca

This paper provided two novel formulations of pimecrolimus including polymeric micelles and thermosensitive hydrogel to treat Keratoconjunctivitis sicca (KCS). KCS is triggered by tear deficiency or excessive tear evaporation, accompanying by eye discomfort and ocular tissue lesions. Its main pathological features are abnormally amplified of corneal epithelial cells, increased inflammatory cell density and levels of inflammatory cytokines, rare conjunctival goblet cell and others. Inflammation mediated by T-cell lymphocytes are considered as the key effectors of KCS in recent studies. Conventional treatment of KCS composes primarily of preservative-free artificial eye drops and anti-inflammatory agents ointments. However, many patients are unresponsive to those treatment, which only offer temporary relief in KCS patients. In addition, more than 90% drug in conventional preparation will be lost when eye blinking. Furthermore, there are multiple barriers hinder drug entry into eye including nasolacrimal drainage, permeability barriers and clearance from the conjunctival vasculature, which bring about only 5% or less bioavailability. Therefore, prolonging drug precorneal residence time, improving permeability and enhancing drug solubility are major concern for eye preparation to treat KCS. Thereby, it is desirable to explore novel preparation loading effective agent to conquer the above problem.Pimecrolimus is a derivative of ascomycin macrolactam and immunosuppressive drug. Pimecrolimus can play anti-inflammatory effective at nanomolar concentrations. It can bind with FK506-binding protein (Macrophilin-12) as the specific binding complexes. The complexes can restrain calcineurin activity in the cytoplasm, thereby inhibiting multiple inflammatory cytokines mRNA transcription expression. However, hydrophobicity of pimecrolimus hindered its clinical translation. Higher corneal permeability and longer residence time are difficult for pimecrolimus, which result into lower bioavailability. Polymeric micelles with nanosize range can provide ophthalmic drug higher corneal permeability and lower corneal stimulation. Polymeric micelle has been regarded as a promising delivery system for the stabilization and solubilization of hydrophobic drugs. The drugs can be physically entraped into the hydrophobic cores of polymeric micelles. This paper prepared pimecrolimus nano-micelle (PNM) using methoxy poly(ethylene glycol)-block-poly (s-caprolactone) (MPEG-PCL) through solid dispersion technique. PNM with the mean particle size of 10-50 nm, which perfectly meet the demand of permeating cornea. To extend the retention time of drugs, we also prepared pimecrolimus micelles in thermosensitive hydrogel system (PTH). PTH has a lower sol-gel transition at around physiological temperature, which makes a pharmaceutical formulation to be easily mixed in the sol state at low temperature. PTH form a gel when applied at the target site, to work as a sustained delivery depot of the drug.PNM was prepared by a solid dispersion method. The in vitro characterizations of PNM and PTH were determined. PNM were investigated by high performance liquid chromatography (HPLC), transmission electron microscopy (TEM), malvern laser particle size and X-ray diffraction (XRD). PNM was homogeneous sphere with particle size of 37.85±1.21 nm and polydisperse index of 0.181±0.023. The drug loading and encapsulation efficiency can reach to 7.57±0.10% and 97.9%±1.02%, respectively. Pimecrolimus can be entrapped in the polymer perfectly. The test tube-inverting method was applied to record the sol-gel-sol phase transition diagram of the aqueous PCEC copolymers solution. As a drug depot, PNH was a free-flowing sol at ambient temperature, and converted into a non-flowing gel at body temperature. In vitro drug release profile showed that PNM and PPH released pimecrolimus for an extent period.Furthermore, KCS mice model were established and induced by benzalkonium chloride to evaluate their in vivo therapeutic effects. PNM, PTH, free pimecrolimus in caster oil (FPO) and commercially available artificial tears were applied to KCS model.The mice aqueous tear production, fluorescein staining score and histopathologic examinations of the cornea at each designed time point were assessed. The results were inspiring, which indicated that PNM can be served as potent ophthalmologic agents for KCS.