Mohammed Asfer

Synthesis and in vitro localization study of curcumin-loaded SPIONs in a micro capillary for simulating a targeted drug delivery system

Nano-sized curcumin-loaded super-paramagnetic iron oxide nanoparticles (CUR-OA-SPIONs) were synthesized chemically by co-precipitation method using oleic acid as a stabilizer and Myrj 52 as a surfactant. The synthesized nanoparticles were characterized for their shape, size, surface morphology, electrokinetic potential, magnetic properties, crystalinity, chemical interactions and thermal transitions. The synthesized CUR-OA-SPIONs were spherical, mono-dispersed, physically stable and super-paramagnetic in nature. In vitro localization study and aggregation dynamics of CUR-OA-SPIONs were studied with a flow of blood inside a square glass capillary (500×500 μm(2) cross section) in the presence of an externally applied magnetic field (Ms=1200 mT). This research which is first of its kind showed the fluorescent imaging of CUR-OA-SPIONs with respect to time to understand the aggregation dynamics of magnetic nanoparticles in a micro capillary simulating the case of targeted drug delivery system. The size of the aggregation increases with respect to time (t=0(+)s to t=500 s), while no significant change in the size of the aggregate was observed after time t=500 s.

Chondroitin sulfate-capped super-paramagnetic iron oxide nanoparticles as potential carriers of doxorubicin hydrochloride

Chondroitin-4-sulfate (CS), a glycosaminoglycan, was used to prepare CS-capped super-paramagnetic iron oxide nanoparticles, which were further employed for loading a water-soluble chemotherapeutic agent (doxorubicin hydrochloride, DOX). CS-capped SPIONs have potential biomedical application in cancer targeting. The optimized formulation had a hydrodynamic size of 91.2±0.8nm (PDI; 0.228±0.004) and zeta potential of -49.1±1.66mV. DOX was loaded onto the formulation up to 2% (w/w) by physical interaction with CS. TEM showed nano-sized particles having a core-shell structure. XRD confirmed crystal phase of iron oxide. FT-IR conceived the interaction of iron oxide with CS as bidentate chelation and also confirmed DOX loading. Vibration sample magnetometry confirmed super-paramagnetic nature of nanoparticles, with saturation magnetization of 0.238emug(-1). In vitro release profile at pH 7.4 showed that 96.67% of DOX was released within 24h (first order kinetics). MTT assay in MCF7 cells showed significantly higher (p<0.0001) cytotoxicity for DOX in SPIONs than DOX solution (IC50 values 6.294±0.4169 and 11.316±0.1102μgmL(-1), respectively).

Passive Vibration Damping Using Polymer Pads With Microchannel Arrays

Passive vibration control using blocks of viscoelastic materials with macro- and microscopic inclusions has been widely investigated. Significant changes in the vibration response have been observed with such inclusions. We have found that their response changes much more significantly if thin microstructures and channels are carved within these materials and are filled with a high-viscosity fluid. In this paper, we report the passive response of a replicated array of oil-filled microchannels, structured within a block made up of polydimethylsiloxane. Constrained and unconstrained vibration-damping experiments are performed on this block, wherein its vibration suppression ability is detected by applying an excitation signal transversely at the geometric center of the lower face of the block. We observe an increase in the fundamental frequency due to change in stiffness of the block and an increase in damping ratio and loss factor owing to the development of a slip boundary condition between the oil and the microchannel walls causing frictional dissipation of the coupled energy. All vibration experiments have been performed using a single-point laser to ascertain the experimental behavior of the system. We have also modeled the vibration suppression characteristics of such systems both analytically and by using simulation tools.

Visualization and Motion of Curcumin Loaded Iron Oxide Nanoparticles During Magnetic Drug Targeting

Magnetic drug targeting (MDT) involves the localization of drug loaded iron oxide nanoparticles (IONPs) around the malignant tissue using external magnetic field for therapeutic purposes. The present in vitro study reports the visualization and motion of curcumin loaded IONPs (CU-IONPs) around the target site inside a microcapillary (500 × 500 μm2 square cross section), in the presence of an externally applied magnetic field. Application of magnetic field leads to transportation and aggregation of CU-IONPs toward the target site inside the capillary adjacent to the magnet. The localization/aggregation of CU-IONPs at the target site shows strong dependence on the strength of the applied magnetic field and flow rate of ferrofluid through the capillary. Such an in vitro study offers a viable for optimization and design of MDT systems for in vivo applications.

Micro-PIV Study of Flow Inside Micro Channel With Surface Mounted Repeated Transverse Ribs

Microchannels are an integral part of various micro devices i.e. micro chemical reactors, fuel cell and electronic packaging etc. There are two important criteria for design of microchannels. The first criterion is the minimization of pressure drop across the microchannel such that the parasitic power requirement is minimized during the operation of these devices. The second criterion is the mixing enhancement due to stronger wall-normal motion of the near wall fluid particles leading to reduction in velocity, temperature and concentration gradient at the wall. Wall surface roughness can be suitably modified for achieving the above objectives in macro-scale flows. Riblets on the channel surface are effective in reducing the frictional resistance for macro flow situations. Various ribs or turbulator geometries have proved to be effective for near wall mixing in heat exchangers and gas turbine blade cooling ducts. However, no systematic study on mixing enhancement due to flow past repeated micro ribs inside microchannel is available in literature. The present study presents the detailed flow past repeated micro-ribs inside a microchannel from micro-PIV (Particle Image Velocimetry) measurements. The microchannel made of Polydimethylsiloxane (PDMS) has been fabricated by PDMS replica moulding. The channel is 50μm × 120μm cross section. The width and height of ribs are 30μm and 10μm respectively. The pitch between the multiple ribs is equal to 100μm. The presence of flow separation at the edge of the rib with generation of vortex structure is not observed at the flow rate set in the present study contrary to the macro flow situations. However, the shear layer is deflected towards the wall with increase in wall-normal velocity indicating possible effectiveness of micro ribs for mixing enhancement in the microchannels.Copyright