Sreeja Balakrishnapillai Suseela

Background: A transdermal drug delivery system has significant benefits over conventional routes; however, its effectiveness is limited by the barrier properties of the stratum corneum. Dissolving microneedles (DMNs) have emerged as a minimally invasive strategy to enhance drug permeation while improving patient compliance. The integration of advanced fabrication techniques such as 3D printing enables precise control over microneedle geometry and reproducibility. Objective: This study aimed to fabricate and characterize pregabalin-loaded PVA/PVP dissolving microneedle arrays using a 3D-printing-assisted mold fabrication approach for efficient transdermal drug delivery. Methods: Microneedle master molds were fabricated using 3D printing, followed by replication using polydimethylsiloxane (PDMS) to obtain negative molds. Pregabalin-loaded bilayer microneedles were prepared using a micromolding technique with PVA/PVP polymers. The formulation was evaluated through rheological analysis, scanning electron microscopy (SEM), mechanical strength testing, insertion studies, swelling behavior, drug loading efficiency, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and in vitro drug release studies. Results: The fabricated microneedles exhibited uniform geometry with sharp tips and no structural defects. Rheological analysis confirmed shear-thinning behavior suitable for mold filling. The microneedles demonstrated adequate mechanical strength (~3.3 N/needle) and efficient insertion into the parafilm model. Drug loading efficiency was high (92.4%), indicating effective encapsulation. FTIR analysis confirmed compatibility between drug and polymers, while DSC and XRD results indicated partial amorphization of pregabalin within the polymer matrix. The formulation showed a biphasic drug release profile with an initial burst followed by sustained release, achieving ~96.8% cumulative release over 24 h. Conclusions: The study successfully demonstrates a robust and reproducible 3D-printing-assisted approach for fabricating pregabalin-loaded dissolving microneedles. The developed system exhibited desirable mechanical, physicochemical, and drug release properties, highlighting its potential as an effective transdermal drug delivery platform.

In this study, we developed electrochemical sensors for detecting blood glucose levels in interstitial fluid over a wide range (0–30 mM) by using a nonenzymatic approach with the nanomaterial MWCNT–chitosan as the glucose-sensing material and incorporating a microneedle for a minimally invasive method. In this method, the sensing principle includes a three-electrode system. The sensor was designed to resemble a screen-printed electrode with a novel microneedle incorporated onto the surface of the electrode. The fabrication process includes a 3-D printing technique followed by the formulation of graphite conductive ink and working-electrode modification with the glucose-sensing material MWCNT–chitosan. Electrochemical characterization studies, such as cyclic voltammetry (CV) and linear sweep voltammetry (LSV), were performed for the MWCNT-chitosan-modified working electrode against Ag/AgCl used as the reference electrode. The measured sensitivity values were 52.44 and 4.224 μA mM⁻¹ cm⁻², limit of detection calculated to be 0.2187 mM and 0.2705 mM using CV and LSV, respectively. To determine the high selectivity toward glucose, an in vitro interference test was performed using common interferents.

The novel design, prototyping, and characterization of an omnidirectional to directional radiation pattern switching planar antenna system are presented. The incorporation of the Yagi‐Uda antenna with an Alford loop antenna is proposed. The antenna is formed by a dipole, driver, reflector, and two directors. In a DC bias switching circuit with a combination of eight SMD PIN diodes and two parasitic elements, the antenna's radiation patterns can be shaped to concentrate energy in an omnidirectional radiation pattern. The introduction of switches using an SMD PIN diode at the arms of the driver element produces two switchable frequencies at 915 MHz and 2.45 GHz. Switches at the directors and reflector control the radiation pattern and can be configured to omnidirectional pattern to directional radiation pattern at those resonance frequencies. The radiation patterns as well as the simulated and measured reflection coefficients (S₁₁) are illustrated and analyzed. Return loss (S₁₁) is observed to be −36.36 dB at resonance frequency of 2.45 GHz (2.35–2.69 GHz) with bandwidth 340 MHz and impedance bandwidth 21.1%, and −24.45 dB at resonance frequency of 915 MHz (854–1006 MHz) with bandwidth 152 MHz and impedance bandwidth 16.61%. When compared with the omnidirectional pattern while maintaining the horizontal polarization, the gain of the antenna increases from 4.6 dBi with 90.02% efficiency to 5.1 dB with 87.77% efficiency in a directional pattern. The developed antenna system's final dimensions are 2.45 λ × 1.80 λ × 0.01 λ. The antenna system is tested in a nuclear reactor containment building equipped with a wireless sensor node. The signal transmission indicates the zero (0) invalid frames with 100 dBm received signal strength indication (RSSI). The printable nature of the antenna architecture and successful transmission of signals across the nuclear reactor containment building make the antenna a good candidate for the wireless sensor node (WSN) in the nuclear reactor.