Micro and Nanosystems - Volume 9, Issue 1, 2017

Background: Biosensor detects the binding event of biologically relevant molecules, which are analyte and ligand. Showing improved sensitivity is the key and primary characteristic of a high-performance biosensor, which displays lower abundance of an analyte. Here, we preferred the silicon substrate on impedance sensor to demonstrate the improvement in the sensitivity with different band-gaps. Methods: we have fabricated two band-gaps on the sensing substrate with the sizes of micrometer and nanometer. These gaps were measured to be 85.5 ± 5 μm and 125 ± 3 nm, respectively. Squamous cell carcinoma (SCC) antibody and antigen interaction for the cancer detection was demonstrated on these gaps. Results: It was found that nano-gap is having higher sensitivity than micro-gap. Further, gold nanoparticle conjugated SCC antigen was found to show the improvement with the micro-gap. Conclusion: This research has evidenced that lesser band-gap (nano) exhibits a good sensitivity for the detection of SCC antigen rather than micro-gap. Gold nanoparticle conjugation with antigen is suitable for microgaps, whereas no significant improvement with nano-gaps was observed.

Background: Drug loaded microparticles are widely used to improve the therapeutic value of various water soluble/insoluble drugs and provides sustained drug release for longer duration of time. Objective: To develop Diclofenac sodium (DS) loaded - ethylcellulose microparticles. Method: Diclofenac sodium (DS) loaded ethylcellulose microparticles were prepared by oil-in-water solvent evaporation method using design of experiments. The effect of three formulation variables (independent variables) like amount of DS, ethylcellulose (EC) and polyvinyl alcohol (PVA) was investigated using 23 experimental design to enhance the encapsulation efficiency (E.E.) (dependent variable) of microparticles. Results: The microparticles were evaluated for surface morphology, E.E., and in vitro drug release. The physicochemical characteristics of the microparticles were assessed using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometry (XRPD), and Field emission scanning electron microscopy. The E.E. of the microparticles was ranged from 37.21 ± 0.87% to 72.20 ± 1.32%. An optimum combination of formulation variables are predicted as 1000 mg DS, 1000 mg EC and 0.1% w/v of PVA, which corresponds to E.E. of 73.71 ± 3.5 % and suitably sustained the DS delivery. Conclusion: The microparticles were found discrete and spherical. The absence of drug polymer interaction was confirmed by FTIR spectroscopy. The XRPD revealed the distribution of drug within the microparticles formulation. In vitro drug release from microparticles showed a sustained drug release pattern over a period of 16 h with initial burst effect.

Objective: A Kenaf composite was prepared by using hand lay-up process. The effect of weather on mechanical, morphology and thermal properties of kenaf composite was studied. Method: Tensile strength of kenaf composite was found to be 60 MPa. Unfortunately, tensile strength of the composite started decreasing after the first weathering month which continued throughout the weathering periods with constant reduction of tensile, reducing almost 85% of the composite mechanical behaviour at the end of the weathering period. Result: The resulting mechanical properties obtained clearly showed that natural fiber and its composites are not able to stand environmental condition because they have poor wettability, incompatibility with some polymeric matrices and high moisture absorption. Due to the high moisture absorption properties, there are formations of void in the composites which can reduce the mechanical properties of composite such as flexural strength or flexural modulus clearly supported by SEM results. Conclusion: It was found that the degree of moisture absorption increased as the exposure time increased. The tensile and flexural properties of kenaf fiber were found decreasing due to moisture induced degradation and the degradation was significant after 2 months. Fortunately, some modifications can be done for improving the mechanical properties, thus, integration of zinc nano particle is proposed; the water repellent capability is good enough to achieve the high performance of the composite with proper system formulation during the modification process and the result of Zinc nano particle reinforced kenaf fiber was shown to have prevented the degradation of the composite.

Objecive: The Response Surface Methodology (RSM) is applied to optimize a passive micromixing unit according to three different targets. Method: To that end several numerical simulations of the low Reynolds number flow in a micromixer, comprising a T-channel and a mixing unit in the main channel, have been conducted. The mixing is enhanced by means of two bars at known angles inside the mixing unit. The input parameter of the optimization process is the distance between bars and, depending on the desired target, different optimal separations are proposed. It has also been assessed how different mixing parameters change when multiple repetitions of the mixing unit, up to 10, are used in the microchannel. Conclusion: This has allowed us to identify the use of 10 units as the best configuration to get the highest efficiency, but the use of 1 unit as the cheapest one, from a mixing cost point of view. Additionally, some configurations have also been assessed as potential chemical microreactors, and it will be shown that they perform better as microreactor than as micromixer.

Background: In the current investigation, oral multiple-unit microparticulate dosage form is produced with the aim of masking the salty (or bitter) taste of etoricoxib (ETX) by incorporating it into hydrophilic polymers (chitosan and polyethylene glycol (PEG))-based microparticles. Objective: The influence of drug loading on ETX liberation from microparticles, the in vitro antiinflammatory activity of ETX either in pure powder form or after its incorporation into microparticles and the ETX taste masking by drug-loaded microparticles were studied. Method: A temperature controlled dispersion technique was used to produce ETX-loaded chitosan-and PEG-based microparticles. Microparticles were characterized in solid state for particle size analysis, drug content, drug liberation, infrared spectroscopy, thin-layer chromatography and scanning electron microscopy. The in vitro anti-inflammatory activity of free and encapsulated ETX was assessed via the protein denaturation bioassay study and taste masking check up was performed in human volunteers. Results: Over the tested dissolution time period of 90 min in 0.01 N HCl (pH 2.0), the increase in initial drug loadings (30-90 mg) decreased the ETX liberation (36 ± 2% for 30 mg ETX vs. 19 ± 1% for 90 mg ETX) from microparticles. No detectible interaction between drug and polymer was noticed but the drug was present in an amorphous or a disordered-crystalline state within the polymer network. Furthermore, the microencapsulation of ETX in hydrophilic polymer matrices did not alter its antiinflammatory activity [50% inhibition (IC50) values of 21 μg/ml and 23 μg/ml were observed respectively for ETX-loaded microparticles and ETX solution after mixing with egg albumin]. Conclusion: The usefulness of this oral microparticulate system in restraining the brain/neuro plasticity associated chronic (or residual) pain occurring at rheumatoid arthritis condition deserves further studies.

Aims: A double-layer dielectric microdisk resonator is proposed. Its refractive index (RI), sensing characteristics, temperature, compensation are studied. Method: By using 3D-finite element method (3D-FEM), the modes and transmission response of the double-layer dielectric microdisk resonator are investigated. Observations: According to the transmission response, there is a critical coupling status when the coupling gap is ~50 nm. With the increasing of the thickness ratio of the polydimethylsiloxane (PDMS) to that of the Si layers, the waveguide sensitivity of RI and temperature decrease sharply, and then changes slowly when the thickness ratio is more than 0.5. Result: The RI sensitivity and detection limit (DL) are ~25 nm/RIU and ~1.1×10-3 RIU, respectively. Conclusion: Compared to traditional microdisk resonator, the double-layer dielectric microdisk resonator achieves temperature compensation due to the upper PDMS layer.

Background: In a conventional approach, development of nanoformulation necessitate significant amount of time, effort and cost. Objective: The current investigation was aimed at studying the impact of statistical central composite face centered (CCF) design on method and process optimization of metformin HCl (MH) loaded poly (D,L-lactide-co-glycolide) (PLGA) nanoformulation. Method: MH loaded PLGA nanoformulations were prepared by solvent evaporation method (SEV) and nanoprecipitation method (NPT) within a validated design space of 2-factor, 3–level CCF design. The effect of independent variables, PLGA and Poloxamer-188 on response variables such as particle size, zetapotential, entrapment efficiency and drug release were evaluated. Desirability approach, contour plots, surface response plots, perturbation plots and sweet spot analysis of graphical optimization technique were employed in nanoformulation. Results: Comparative study of optimized nanoformulations of SEV, NPT methods by CCF design reveal that both methods produce spherical shape particles of nanosize, with homogenous distribution and good drug entrapment efficiency. Nanoprecipitation method is proven as the best optimized method, composed of nanoformulation of 1.0%, w/v PLGA and 0.680%, w/v Poloxamer exhibited mean particle size of 110.8 nm, entrapment efficiency of 71.62% and drug release 88.85% at 12hrs, in comparison to solvent evaporation method. Conclusion: These research findings not only emphasize the understanding of CCF design as a promising optimization tool for method and formulation process development of MH loaded PLGA nanoformulations, but are also a worthwhile option time and efforts involved in complex and complicated formulation development process of nanoformulations for successful commercialization.

Background: The most popular photorefractive material is BaTiO3 due to its large electrooptic coefficients (EO) as well as its dielectric properties at room temperature. Objective: The doping of this crystal with rhodium (BaTiO3: Rh) has as a main goal to investigate possibility of working near infrared domaine (I.R). Method: In this paper, we propose an experiment of the evolution of the electro-optical coefficient (EO) r33 and dielectric constant ε33 as function of temperature from 20°C to 50°C for a new crystal BaTiO3: Rh. Result: We show that electro-optic and dielectric properties are the same behavior versus temperature variation.