Research paper Investigation of preparation parameters of nanosuspension by top-down media milling to improve the dissolution of poorly water-soluble glyburide Sachin Kumar Singh a,e,⇑ , K.K. Srinivasan b , K. Gowthamarajan c , Dhananjay S. Singare d , Dev Prakash a , Narayan Babulal Gaikwad a a Department of Pharmacy, Karpagam University, Coimbatore, India b Department of Pharmaceutical Chemistry, Manipal University, Manipal, India c Department of Pharmaceutics, JSS College of Pharmacy, Ooty, India d Custom Pharmaceutical Services-Formulations, Dr. Reddys Laboratories Ltd., Hyderabad, India e Department of Pharmaceutical Analysis, Bharathi College of Pharmacy, Bharathinagara, India article info Article history: Received 24 January 2011 Accepted in revised form 16 March 2011 Available online 23 March 2011 Keywords: Bead mill Zeta potential Nanosuspension Mean particle size d(90) X-ray powder diffraction Unmilled drug abstract The objective of this study was to identify and optimize formulation and process variables affecting char- acteristic and scale-up of nanosuspension manufacturing process on bead mill considering industrial per- spective. Formulation factors evaluated were ratio of polymer to drug and ratio of surfactant to drug, whereas process parameters were milling time and milling speed. Responses measured in this study include zeta potential and mean particle size d(90). The test revealed that ratio of polymer to drug and milling speed have significant effect on zeta potential whereas milling time and milling speed have sig- nificant effect on the particle size distribution of nanosuspension. The X-ray powder diffraction pattern of drug milled at high and low speed reveals no form conversion when compared with unmilled drug. The formulated nanosuspension has shown a faster dissolution profile (98.97% in 10 min), relative to that of raw glyburide (18.17% in 10 min), mainly due to the formation of nanosized particles. The ANOVA test revealed that there was no significant difference in the dissolution profiles of fresh and aged nanosuspen- sion. These results indicate the suitability of formulation procedure for preparation of nanosized poorly water-soluble drug with significantly improved in vitro dissolution rate and thus possibly enhance fast onset of therapeutic drug effect. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Nanosuspensions are liquid dispersion consisting of solid drug nanoparticles, which are stabilized by polymer and/or surfactant. Nanosizing has been proven to be an effective tool for an active moiety considered as ‘‘brick dust candidate’’. There are two main approaches for formulating a nanosuspension i.e., top-down and bottom up technology. The bottom up technology involves dissolv- ing drug in a solvent, to which a nonsolvent is then added to precipitate the crystals .The top-down approach relies on mechan- ical attrition to render large crystalline particles into nanoparticles. The ‘Top-Down Technologies’ include media milling (Nanocrys- tals Ò ), high-pressure homogenization in water (Dissocubes Ò ), high-pressure homogenization in nonaqueous media (Nanopure Ò ) and combination of precipitation and high-pressure homogeniza- tion (Nanoedege Ò ). Table 1 lists some of the FDA approved prod- ucts relying on nanotechnology. Nanosuspensions for oral route are mainly characterized by mean particle size d(90), zeta poten- tial, crystalline status, dissolution velocity, and saturation solubil- ity. A particle of less than 400 nm is considered to be acceptable for a nanosuspension to be administered intravenously [1]. For a physically stable nanosuspension solely stabilized by electrostatic repulsion, a zeta potential of ±30 mV is required as a minimum. In the case of a combined electrostatic and steric stabilization, a rough guide line of ±20 mV is sufficient [2]. The crystalline struc- ture of nanosuspension is important for drugs existing in different polymorphic forms. This is mainly confirmed by DSC, X-RD, or wide angle X-ray analysis (WAXS). Dissolution velocity and satura- tion solubility are generally performed using official pharmacopoe- ial methods. The stability and robustness of a nanosuspension are mainly governed by various formulation and process variables. Selection of proper steric and electrostatic stabilizer and its opti- mum quantity plays a major role in formulating a nanosuspension. Commonly used steric stabilizer includes hydroxypropylmethyl cellulose (HPMC), hydroxypropyl cellulose (HPC), povidone (PVP K-30), and pluronics (F68 and F127) whereas electrostatic 0939-6411/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ejpb.2011.03.014 ⇑ Corresponding author. Department of Pharmaceutical Analysis, Bharathi Col- lege of Pharmacy, Bharathinagara 571422, Maddur Tq., Mandya Dist., Karnataka, India. Tel.: +91 725965393. E-mail addresses: sachin_pharma06@yahoo.co.in, singhsachin23@gmail.com (S.K. Singh). European Journal of Pharmaceutics and Biopharmaceutics 78 (2011) 441–446 Contents lists available at ScienceDirect European Journal of Pharmaceutics and Biopharmaceutics journal homepage: www.elsevier.com/locate/ejpb