BioElectronics (United States)

Objective.Neuroprosthetic devices require multichannel stimulator systems with an increasing number of channels. However, there are inherent power losses in typical multichannel stimulation circuits caused by mismatches between the power supply voltage and the voltage required at each electrode to successfully stimulate tissue. This imposes a bottleneck towards high-channel-count devices, which is particularly severe in wirelessly-powered devices. Hence, advances in the power efficiency of stimulation systems are critical. To support these advances, this paper presents a methodology to identify and quantify power losses associated with different power supply scaling strategies in multichannel stimulation systems.Approach.The methodology uses distributions of stimulation amplitudes and electrode impedances to calculate power losses in multichannel systems. Experimental data from prior studies spanning various stimulation applications were analyzed to evaluate the performance of fixed, global, and stepped supply scaling methods, focusing on their impact on power dissipation and efficiency.Main Results.Variability in output conditions results in low power efficiency in multichannel stimulation systems across all applications. Stepped voltage scaling demonstrates substantial efficiency improvements, achieving an increase of 43% to 100%, particularly in high-channel-count applications with significant variability in tissue impedance. In contrast, global scaling proved effective only in systems with fewer channels and minimal inter-channel variation.Significance.The findings highlight the importance of tailoring power management strategies to specific applications to optimize efficiency while minimizing system complexity. The proposed methodology provides a framework for evaluating trade-offs between efficiency and system complexity, facilitating the design of more scalable and power-efficient neurostimulation systems.

ABSTRACT Biomaterials for bone regeneration, additionally to providing structural support and delivering of key biological signals, must promote the recruitment and growth of local progenitor cells. While synthetic biomaterials are tailorable regarding stability and bioactivity, their mesh size often requires proteolytic remodeling for cells to infiltrate and thereby can significantly restrict the progress of regeneration. Here, to improve the recruitment of osteogenic cells, microporous biomaterials with various degrees of stiffness are formed by the confinement of transglutaminase crosslinked polyethylene glycol (TG‐PEG) microgels. Confined microgels are found to be suitable substrates for human bone marrow stromal cells (hBM‐MSCs), that with increasing stiffness reveal improved spreading, Yes‐associated protein (YAP) activation, and heightened recruitment of cells mediated by platelet‐derived growth factor (PDGF)‐BB. Furthermore, upon stimulation with bone morphogenetic protein (BMP)‐2, osteogenic differentiation of hBM‐MSCs is found to be superior when cultured on stiff microgels as compared to encapsulation in bulk hydrogels. Even more compelling, TG‐PEG microgels enable a stiffness‐dependent recruitment of cells from bone defects in vitro. The combination of tunable stiffness and microscale pore structures in microgels provides new perspectives on the design of advanced scaffolds for bone healing, with the potential to improve clinical outcomes in regenerative medicine.

The dispersion coefficient of the constant phase element (CPE) is typically treated as an empirical fitting parameter in the analysis of impedance spectroscopy data, with no clear physical meaning. Here, we present an energy-based interpretation for this coefficient by linking it to the ratio of the dissipated or stored energy in the CPE relative to that supplied by the input source. Using the RC network equivalency of a CPE, we decompose the total input energy into a contribution stored in the capacitive modes and another dissipated in the resistive modes. Analytical expressions of these energy quantities are derived for three test examples: (i) a constant voltage, (ii) a voltage ramp, and (iii) a quadratic input of the form v(t) = λt2. In all cases, we found that the ratios of any two of these energy quantities reduce to pure functions of the dispersion coefficient of the CPE, independent of excitation amplitude or material parameters. This result provides a new perspective on the CPE’s dispersion coefficient from a thermodynamic/energetic basis, with direct implications for supercapacitor characterization, battery modeling, as well as for the analysis of other electrochemical devices and systems exhibiting the CPE behavior.

This work presents the design and analysis of a 2.4 GHz Low Noise Amplifier (LNA) using the CMOS 180nm technique optimized for high gain, low noise figure, and improved linearity. The proposed LNA is implemented using cascode and folded cascode topologies with inductive source degeneration to enhance impedance matching and noise performance. Additionally, Modified Derivative Superposition (MDS) is employed to improve linearity by suppressing third-order intermodulation distortion (IMD3). The design achieves a noise figure below 0.6 dB, open-loop gain exceeding 30 dB, and ensures stability across operating conditions. This combination of performance metrics offers a superior gain-noise trade-off compared to other recent works, making it highly suitable for demanding applications in the congested 2.4 GHz band. Performance metrics like IIP3, OIP3, and P1dB are analyzed to validate linearity, while S-parameters are examined to evaluate impedance matching, gain, and stability across the operating frequency. The simulation results demonstrate significant improvements in gain, noise performance, and power efficiency, making the proposed LNA a promising solution for modern wireless communication systems systems such as high-performance IoT nodes, Wi-Fi 6/7, and Bluetooth receivers, where sensitivity and resilience to interference are critical.

Conceptual frameworks that describe the electronic structure of molecules are an integral part of understanding chemical structures and reaction mechanisms and designing organic compounds. Here we develop a preliminary set of design guidelines for controlling the electronic structure of DNA. Recent work indicates that charge delocalization occurs over several bases and results in coherence lengths greater than a single base pair. To examine the interactions between bases and their effects on delocalization, this study investigates the influence of nearest-neighbour base pair interactions on the charge transport properties of DNA duplexes that are predominantly composed of guanine-cytosine base pairs. Results show that, by manipulating the sequence, the conductance can be substantially modified without altering the molecular composition. The electronic density of states are then analysed to deduce a set of design guidelines aimed at maintaining high conductance values in long duplexes. Utilizing these rules, we demonstrate that 20-base-pair DNA sequences can exhibit conductance values surpassing 1 × 10-3G0.

ABSTRACT The rise in pancreatic diseases, resulting from improved living quality and lifestyle habits changes, has imposed a serious social burden. To better understand the pancreatic functions during disease progression, constructing a bionic pancreas is vital yet challenging in tissue engineering. Herein, inspired by the physiological anatomy of the pancreas, we introduce core‐shell microfibers with pancreatic stellate cells (PSCs) in the shell and pancreatic β‐cells in the core. Compared to traditional plate culture, the β‐cells encapsulated in the microfiber exhibit enhanced glucose‐stimulated insulin secretion. Such microfibers also serve as a platform to study the progression of diabetes of the exocrine pancreas, where the PSCs are activated under conditions of pancreatic exocrine diseases such as chronic pancreatitis. The activated PSCs impede insulin synthesis and increase apoptosis in β‐cells, resulting in elevated blood glucose. This high‐glucose microenvironment further exacerbates the activation of PSCs, causing a vicious cycle of diabetes. Additionally, the bio‐inspired pancreas also demonstrates its potential in drug screening, as evidenced by testing the glucagon‐like peptide 1 receptor agonist, Exendin‐4. Building upon such features, it is convincing that these multi‐component microfibers hold promise for exploring the pancreatic exocrine and endocrine interactions, and showing potential in disease modeling, drug screening, and regenerative medicine.

Abstract Self‐assembling DNA crystals have emerged over the last two decades as an efficient and effective means of organizing matter at the nanoscale, but functionalization of these lattices has proved challenging as physiological buffer conditions are required to maintain structural integrity. In this manuscript, we demonstrate the silicification of mesoporous DNA crystals using sol–gel chemistry. We identify reaction conditions that produce the minimum coating thickness to confer environmental protection, and we subsequently measure this protective ability to various stressors, including heat, low ionic strength solution, organic solvents, and unprotected freezing. By soaking metal ions and dyes into the lattice after silica coating, we demonstrate that the crystals maintain their pores and that the major groove of the DNA can still be used as a sequence‐specific template for chemical reactions. We image a library of different crystal motifs by electron microscopy, and we perform X‐ray diffraction on these crystals, both with and without cryoprotection, to determine the structure of the DNA frame, underscoring the conserved molecular order after coating. We anticipate these mesoporous silica composites will find use in applications involving extreme, nonphysiological conditions and in experiments which utilize the DNA glass described here as a template for chemical reactions on the internal surface of architected materials.

In the design of ultra-low-noise biosensing analog front-ends, input stage noise optimization remains a critical challenge. This paper presents a reconfigurable capacitive transimpedance amplifier designed for broadband biosensing applications with optimized noise performance. The proposed architecture employs a digitally controlled biasing scheme that adaptively configures the geometry and bias current of the input stage according to the sensor capacitance and target bandwidth. Post-layout simulations in a 40 nm CMOS process demonstrate a consistent transimpedance gain of $154.5 \mathrm{~dB} \Omega$ across all configurations, with bandwidth scalable from 3 MHz to 82.3 MHz. Input-referred noise is minimized over a sensor capacitance range of 0.4 pF to 6 pF. For a sensor capacitance of 4 pF, the simulation result shows 29.7 pA and 7.3 nA input-referred RMS noise at 500 kHz and 80 MHz bandwidth, respectively. The proposed front-end achieves improved noise efficiency with increasing bandwidth, making it suitable for measurements of ion channels, nanopores, and other biosensing applications.