Nanoprecipitation-Enhanced Sensitivity in Enzymatic Nanofluidic Biosensors.

Single nanochannels show unique transport properties due to nanoconfinement. It has been demonstrated that at submillimolar concentrations of divalent cations, a nanoprecipitation reaction can occur in nanochannels. Although several reports have shown, described, and modeled the nanoprecipitation process, no further advantages have been taken from this phenomenon. Here, we show that the nanoprecipitation reaction can be incorporated into enzyme-modified nanochannels to enhance the performance of small-molecule biosensors via in situ amplification reactions. Contrary to the working principle of previous enzymatic nanofluidic biosensors, the nanofluidic biosensor described in this work operates on the basis of concerted functions: pH-shifting enzymatic activity and nanoprecipitation. We show that the simple addition of Ca2+ and Mg2+ ions in the working analyte solution containing urea can lower the detection limit from the nanometer to the subnanometer regime and modulate the dynamic linear range. This approach enables the implementation of more sensitive real-time nanofluidic detection methods without increasing the complexity of the nanofluidic platform or the sensing approach. We envision that the integration of concerted functions in nanofluidic architectures will play a key role in expanding the use of these nanoscale devices for analytical purposes.

Noninvasive and Multiplex Self-Test of Kidney Disease Biomarkers with Graphene-Based Lab-on-a-Chip (G-LOC): Toward Digital Diagnostics in the Hands of Patients.

Chronic kidney disease is one of the major health issues worldwide. However, diagnosis is now highly centralized in large laboratories, resulting in low access to patient monitoring and poor personalized treatments. This work reports the development of a graphene-based lab-on-a-chip (G-LOC) for the digital testing of renal function biomarkers in serum and saliva samples. G-LOC integrates multiple bioelectronic sensors with a microfluidic system that enables multiplex self-testing of urea, potassium, sodium, and chloride. The linearity, limit of detection (LOD), accuracy, and coefficient of variability (CV) were studied. Accuracy values higher than 95.5% and CV lower than 9% were obtained for all of the biomarkers. The analytical performance was compared against three reference lab benchtop analyzers by measuring healthy- and renal-failure-level samples of serum. From receiver operating characteristic (ROC) plots, sensitivities (%) of 99.7, 97.6, 99.1, and 89.0 were obtained for urea, potassium, sodium, and chloride, respectively. Then, the test was evaluated in noninvasive saliva samples and compared against reference methods. Correlation and Bland-Altman plots showed good correlation and agreement of the G-LOC with the reference methods. It is noteworthy that the precision of G-LOC was similar to better than benchtop lab analyzers, with the advantage of being highly portable. Finally, a user testing study was conducted. The analytical performance obtained with untrained volunteers was similar to that obtained with trained chemists. Additionally, based on a user experience survey, G-LOC was found to have very simple usability and would be suitable for at-home diagnostics.

Unified Roadmap for ZIF-8 Nucleation and Growth: Machine Learning Analysis of Synthetic Variables and Their Impact on Particle Size and Morphology.

Metal-organic frameworks (MOFs) have settled in the scientific community over the last decades as versatile materials with several applications. Among those, zeolitic imidazolate framework 8 (ZIF-8) is a well-known MOF that has been applied in various and diverse fields, from drug-delivery platforms to microelectronics. However, the complex role played by the reaction parameters in controlling the size and morphology of ZIF-8 particles is still not fully understood. Even further, many individual reports propose different nucleation and growth mechanisms for ZIF-8, thus creating a fragmented view for the behavior of the system. To provide a unified view, we have generated a comprehensive data set of synthetic conditions and their final outputs and applied machine learning techniques to analyze the data. Our approach has enabled us to identify the nucleation and growth mechanisms operating for ZIF-8 in a given sub-space of synthetic variables space (chemical space) and to reveal their impact on important features such as final particle size and morphology. By doing so, we draw connections and establish a hierarchy for the role of each synthetic variable and provide with rule of thumb for attaining control on the final particle size. Our results provide a unified roadmap for the nucleation and growth mechanisms of ZIF-8 in agreement with mainstream reported trends, which can guide the rational design of ZIF-8 particles which ultimately determine their suitability for any given targeted application. Altogether, our work represents a step forward in seeking control of the properties of MOFs through a deeper understanding of the rationale behind the synthesis procedures employed for their synthesis.

Insight into the transport of ions from salts of moderated solubility through nanochannels: negative incremental resistance assisted by geometry.

In this study, the transport of salt with moderate solubility through bioinspired solid-state nanochannels was comprehensively investigated. For this purpose, bullet-shaped channels were fabricated and exposed to KClO4, a monovalent salt with moderate solubility. These channels displayed the typical rectifying behavior characteristic of asymmetrical channels but with one remarkable difference, the iontronic output exhibited a negative incremental resistance phenomenon of high gating efficiency when the transmembrane voltage in the open state was increased enough, giving rise to an inactivated state characterized by a low and stable ion current. The behavior is attributed to salt precipitation inside the channel and remarkably, it is not observed in other geometries such as cylindrical or cigar-shaped channels. Considering the central role of the surface in precipitation formation, the influence of several parameters such as electrolyte concentration, pH, and channel size was studied. Under optimized conditions, this system can alternate among three different conductance states (closed, open, and inactivated) and exhibits gating ratios higher than 20. Beyond its potential application in fields related to electronics or sensing, this study provides valuable insight into the fundamental principles behind ion rectifying behavior in solid-state channels and highlights the implications of surface phenomena at the nanoscale.

Manipulating Ion Transport Regimes in Nanomembranes via a "Pore-in-Pore" Approach Enabled by the Synergy of Metal-Organic Frameworks and Solid-State Nanochannels.

Solid-state nanochannels (SSNs) have emerged as promising platforms for controlling ionic transport at the nanoscale. SSNs are highly versatile, and this feature can be enhanced through their combination with porous materials such as Metal-Organic Frameworks (MOF). By selection of specific building blocks and experimental conditions, different MOF architectures can be obtained, and this can influence the ionic transport properties through the nanochannel. Herein, we study the effects of confined synthesis of Zr-based UiO-66 MOF on the ion transport properties of single bullet-shaped poly(ethylene terephthalate) (PET) nanochannels. We have found that emerging textural properties from the MOF phase play a determinant role in controlling ionic transport through the nanochannel. We demonstrate that a transition from ion current saturation regimes to diode-like regimes can be obtained by employing different synthetic approaches, namely, counterdiffusion synthesis, where MOF precursors are kept separate and forced to diffuse through the nanochannel, and one-pot synthesis, where both precursors are placed at both ends of the channel. Also, by considering the dependence of the charge state of the UiO-66 MOF on the protonation degree, pH changes offered a mechanism to tune the iontronic output (and selectivity) among different regimes, including anion-driven rectification, cation-driven rectification, ion current saturation, and ohmic behavior. Furthermore, Poisson-Nernst-Planck (PNP) simulations were employed to rationalize the different iontronic outputs observed experimentally for membranes modified by different methods. Our results demonstrate a straightforward tool to synthesize MOF-based SSN membranes with tunable ion transport regimes.

Poly(allylamine)-tripolyphosphate polymeric nanoparticle as an NLRP3-dependent systemic adjuvant for the vaccine development.

Nanotechnology plays a crucial role in vaccine development and provides the opportunity to design functional nanoparticles (Np) of different compositions, sizes, charges and surface properties for biomedical applications. The present study aims to evaluate a complex coacervate-like Np composed of poly(allylamine hydrochloride) (PAH) and tripolyphosphate (Tpp) as a safe vehicle and adjuvant for systemic vaccines. We investigated the activation of different antigen-presenting cells (APCs) with Np-PAH and its adjuvanticity in Balbc/c and different KO mice that were intraperitoneally immunized with Np-OVA. We found that Np-PAH increased the expression of CD86 and MHCII and promoted the production and secretion of interleukin-1ß (IL-1ß) and IL-18 through the inflammasome NLRP3 when macrophages and dendritic cells were co-incubated with LPS and Np-PAH. We evidenced an unconventional IL-1ß release through the autophagosome pathway. The inhibition of autophagy with 3-methyladenine reduced the LPS/Np-PAH-induced IL-1ß secretion. Additionally, our findings showed that the systemic administration of mice with Np-OVA triggered a significant induction of serum OVA-specific IgG and IgG2a, an increased secretion of IFN-γ by spleen cells, and high frequencies of LT CD4 + IFN-γ + and LT CD8 + IFN-γ + . In conclusion, our findings show that PAH-based Np promoted the inflammasome activation of innate cells with Th1-dependent adjuvant properties, making them valuable for formulating of novel preventive or therapeutic vaccines for infectious and non-infectious diseases.