Micro and Nanosystems - Online First

Photonic crystal fibers (PCFs) are increasingly used for optical sensing due to their tunable structural and dispersion properties. Pressure sensing with PCFs is of interest, but current designs often have nonlinear sensitivity and limitations at high pressures.

This study introduces a novel water-filled PCF design to achieve enhanced pressure sensitivity by utilizing water's compressibility to improve chromatic dispersion responsiveness.

Numerical simulations were conducted to analyze how pressure affects chromatic dispersion and birefringence in both polarization modes of the proposed PCF.

The water-filled PCF demonstrates a linear increase in pressure sensitivity, with the y-polarization mode reaching 100-185 ps/nm-km/bar at 200 bar and the x-polarization mode reaching 115-70 ps/nm-km/bar. This is a significant improvement over conventional air-filled PCFs, which show a nonlinear decrease in sensitivity with increasing pressure (47-30 ps/nm-km/bar for x-polarization and 60-40 ps/nm-km/bar for y-polarization).

The proposed water-filled PCF design offers superior pressure sensitivity, making it a promising candidate for high-precision pressure sensing applications in various fields.

Many drugs come under the category of the biopharmaceutical classification system (BCS) class II. Such drugs are insoluble in water due to their high log P value and when applied topically remain in the stratum corneum of the skin and very few amounts pass through the skin, thus producing under-medication.

The main aim of this study is to prepare a drug-loaded nanoemulsion-based topical gel that shows the sufficient stability and the ability to permeate a sufficient amount of drug through the skin for improving the topical application of the drug. For such purpose, tacrolimus (TL) was used as a drug candidate in this research and it belongs to BCS class II.

After screening of oil, surfactant, and co-surfactant, the outline of pseudo ternary phase was fabricated involving the walnut as the oil phase at three Smix proportions (2:1, 1:1, and 1:2; Tween 80: transcutosol). The different formulations of nano-emulsion were prepared using the various ratios of walnut to Smix ratio (1:1 to 1:6) and water content, and an optimized formulation was used to fabricate the gel. For optimizing the nano-emulgel, the different formulations were prepared using the varying ratio of drug to carbopol 940 ranging from 1:1 to 1:13.5. All the prepared formulations of lacrolimus-loaded nano-emulgel were undergone for their characterization considering certain parameters like; spreadability, extrudability, viscosity, and pH. The optimized nano-emulgel was also further evaluated for their quality checking.

Results indicated that the nano-emulsion area was significant in the Smix ratio of 2:1. Scanning electron microscopy (SEM) exhibited that spherical and non-cumulative oil globules were present in optimized nano-emulsion having a size <200 nm. The poly-dispersity index (PDI) of such nano-emulsion was 0.237 which was the lowest among all prepared formulations. The various formulation of nano-emulgel was prepared using Carbopol-940 as a gelling agent in varied concentrations and optimized nano-emulgel showed an improved diffusion rate in comparison to bulk drug. Results also showed that the bulk drug did not show absolute diffusion during the test period and only 36.4% of the drug was released after 24 hrs. However, the optimized formulation of tacrolimus-loaded nano-emulgel exhibited a significant enhancement in their diffusion rate, since about 11% of the drug was diffused in the first hour and almost 93% of the drug was diffused in the 24-hour test period. The pH of all prepared nanomulgel was in the range of 5.4 to 6.1 which is safe to be used on the skin. Morphological characterization and stability study were also assessed for the optimized nano-emulgel and the result revealed that the optimized formulation stored at 25^oC temperature and 60% relative humidity was stable and no significant changes were observed in their stability parameters up to 3 months.

Results showed that nano-emulgel may be a suitable carrier for the tacrolimus-like BCS class-II drugs that can penetrate a large amount of drug through the skin due to having nano-size globules. Thus, it can be concluded that when tacrolimus like other drugs is required to be applied topically, the prepared nano-emulgel like other formulations may be a significant alternative that has great potential to rectify the permeability issue and ultimately may improve the topical application of the drug.