Solid lipid nanoparticles are at the forefront of the rapidly developing field of nanotechnology with several potential applications in drug delivery, clinical medicine and research, as well as in other varied sciences. Due to their unique size-dependent properties, lipid nanoparticles offer the possibility to develop new therapeutics. The ability to incorporate drugs into nanocarriers offers a new prototype in drug delivery that could be used for secondary and tertiary levels of drug targeting. Hence, solid lipid nanoparticles hold great promise for reaching the goal of controlled and site specific drug delivery and hence have attracted wide attention of researchers. This review presents a broad treatment of solid lipid nanoparticles discussing their advantages, limitations and their possible remedies. The different types of nanocarriers which were based on solid lipid like solid lipid nanoparticles, nanostructured lipid carriers, lipid drug conjugates are discussed with their structural differences. Different production methods which are suitable for large scale production and applications of solid lipid nanoparticles are described. Appropriate analytical techniques for characterization of solid lipid nanoparticles like photon correlation spectroscopy, scanning electron microscopy, differential scanning calorimetry are highlighted. Aspects of solid lipid nanoparticles route of administration and their biodistribution are also incorporated. If appropriately investigated, solid lipid nanoparticles may open new vistas in therapy of complex diseases.

The authors’ research work into fully developed pulsating and oscillating laminar pipe and channel flows raised questions regarding the development length of the corresponding steady flow. For this development length, i.e., the distance from the entrance of the pipe to the axial position where the flow reaches the parabolic velocity profile of the Hagen-Poiseuille flow, a wide range of contradictory data exists. This is shown through a short review of the existing literature. Superimposed diffusion and convection, together with order of magnitude considerations, suggest that the normalized development length can be expressed as L∕D=C0+C1Re and for Re→0 one obtains C0=0.619, whereas for Re→∞ one obtains C1=0.0567. This relationship is given only once in the literature and it is presumed to be valid for all Reynolds numbers. Numerical studies show that it is only valid for Re→0 and Re→∞. The development length of laminar, plane channel flow was also investigated. The authors obtained similar results to those for the pipe flow: L∕D=C0′+C1′; Re, where C0′=0.631 and C1′=0.044. Finally, correlations are given to express L∕D analytically for the entire Re range for both laminar pipe and channel flows.

Celecoxib (4-[5-(4-methylphenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-benzenesulfonamide, is a specific cyclooxygenase-2 (COX-2) inhibitor with no inhibition of cyclooxygenase-1 at therapeutic doses. It is being used successfully for the treatment of rheumatoid arthritis, osteoarthritis, acute pain, familial adenomatous polyposis and primary dysmenorrhea. 1,2) Celecoxib also demonstrated significant chemopreventive activity in colon carcinogenesis, ultraviolet B radiation (UVB) induced skin cancer and breast cancer. [3][4][5] Celecoxib is weakly acidic (pK a is 11.1) and hydrophobic (Log P is 3.5) and its low aqueous solubility (3-7 mg/ml) contributes to high variability in absorption after oral administration. 6)The molecule exists in three polymorphic forms and its solid-state interconversion between the forms at ordinary temperatures has not been observed. It is isolated as agglomerates of long needle-shaped crystals, which exhibit cohesiveness, low bulk density and compressibility, and poor flow properties that impart complications in it's processing into solid dosage forms.7) According to biopharmaceutical classification system, celecoxib is classified as a low solubility and high permeability drug. 6) Therefore, the particle size of celecoxib influences the content uniformity, dissolution and bioavailability of the product. The t max of celecoxib is about three hours after oral administration. Rapid onset of action is necessary to provide fast pain relief in the treatment of acute pain. Therefore, it is necessary to enhance the aqueous solubility and dissolution rate of celecoxib to obtain faster onset of action, to minimize the variability in absorption and improve its overall oral bioavailability. This can be achieved by formulating the drug in lipid-based systems.Among the lipid-based systems, self-microemulsifying drug delivery system (SMEDDS) is a promising technology to improve the rate and extent of the absorption of poorly water-soluble drugs. [8][9][10][11][12][13][14][15] The clinical usefulness of the SMEDDS is evident from the commercially available formulations containing cyclosporin A, ritonavir and Saquinavir. 16,17) SMEDDS are comprised of mixture of drug, oil, surfactant(s) and/or co-solvents which form fine oil in water and/or water in oil microemulsions upon dilution with aqueous medium or in vivo administration. SMEDDS enhances the bioavailability of poorly water-soluble drugs through solubilization in the excipient matrix or interface and dispersion in the gastrointestinal tract. Relatively small size of the dispersed oil droplets in nanometer range and very high surface area to volume ratio are advantages of the microemulsion. These characteristics result in faster drug release from microemulsion in a reproducible manner, which can be designed further to make the release characteristics independent of the gastro intestinal physiology and the fed/fasted state of the patient. 8,[18][19][20] In this study, we have developed an optimized formulation using a self-microemulsifying system in...

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