Formulation of GOFA nanocrystals suspension.

Purpose. To prepare and characterize nanocrystals of GOFA [3-(4’-geranyloxy-3’-methoxyphenyl)-2-trans propenoic acid], a natural anti-inflammatory agent, in order to improve its solubility and delivery. Methods. GOFA was produced by one-pot, two-step synthesis. Briefly, the methyl ester of ferulic acid was treated, first, with geranyl bromide and K2CO3 and then with a basic medium to obtain the final product. GOFA crystals were produced using the solvent injection method. Briefly, 30 mg of GOFA were dissolved in 5 ml of acetone and injected using a syringe in distilled water (60°C) containing 1% (w/v) of Pluronic® F68 after stirring. After complete acetone evaporation, the suspension was processed by high speed stirring (5 min, 8000rpm, Ultra-turrax, IKA) and then homogenized using a high pressure homogenizer (30 cycles, 150000 psi; Emulsiflex-C5, Avestin, Canada). Crystal dimensions were determined by photon correlation spectroscopy every 5 homogenization cycles. The nanocrystal suspension was then lyophilized using different cryoprotectors (e.g., mannitol; trehalose; PEG, 10KDa; PVA, 15 KDa; CMC) and the crystal size was analyzed after resuspension. Results. GOFA was obtained with a overall yield of 98%. The solvent injection produced micrometric needle-like crystals with a strong birefringence. The first five homogenization cycles drastically reduced the crystal size down to ≈500 nm, while the following 20 cycles gradually reduced the mean dimensions to ≈420 nm. No further reductions were observed with the next five cycles. Nanocrystals prepared by 20 homogenization cycles (≈440 nm) were lyophilized in presence of various cryoprotectors. After re-suspension nanocrystals maintained the original size only when PVA was used as cryoprotector while, in the case of trehalose and mannitol, the crystal sizes increased of 100 and 250 nm, respectively. The other cryoprotectors investigated were not able to prevent crystal aggregation. Conclusion. GOFA was successfully formulated as nanocrystal suspension. The use of an adequate cryoprotector led to the production of a stable dry powder re-dispersible extemporaneously.