Mineral-element-chelating activity of food-derived peptides: influencing factors and enhancement strategies.

Mineral elements including calcium, iron, and zinc play crucial roles in human health. Their deficiency causes public health risk globally. Commercial mineral supplements have limitations; therefore, alternatives with better solubility, bioavailability, and safety are needed. Chelates of food-derived peptides and mineral elements exhibit advantages in terms of stability, absorption rate, and safety. However, low binding efficiency limits their application. Extensive studies have focused on understanding and enhancing the chelating activity of food-derived peptides with mineral elements. This includes obtaining peptides with high chelating activity, elucidating interaction mechanisms, optimizing chelation conditions, and developing techniques to enhance the chelating activity. This review provides a comprehensive theoretical basis for the development and utilization of food-derived peptide-mineral element chelates in the food industry. Efforts to address the challenge of low binding rates between peptides and mineral elements have yielded promising results. Optimization of peptide sources, enzymatic hydrolysis processes, and purification schemes have helped in obtaining peptides with high chelating activity. The understanding of interaction mechanisms has been enhanced through advanced separation techniques and molecular simulation calculations. Optimizing chelation process conditions, including pH and temperature, can help in achieving high binding rates. Methods including phosphorylation modification and ultrasonic treatment can enhance the chelating activity.

Stem cell-derived exosomes for chronic wound repair.

Stem cells possess the capability of self-renewal and multipotency, which endows them with great application potential in wound repair fields. Yet, several problems including immune concerns, ethical debates, and oncogenicity impede the broad and deep advance of stem cell-based products. Recently, owing to their abundant resources, excellent biocompatibility, and ease of being engineered, stem cell-derived exosomes were proved to be promising nanomedicine for curing chronic wounds. What is more, stem cell-derived exosomes are almost the mini record of their maternal cells, which even equipped them with the unique characteristics of stem cells. Chronic wound healing efficacy is dominated by several complicated factors, especially the excessive inflammation conditions and impaired vessels. Therefore, this review tries to concentrate on the current advances of stem cell-derived exosomes for reducing inflammation and promoting angiogenesis in chronic wound healing processes. Last but not least, the existing limitations and future perspectives of stem cell-derived exosomes for chronic wound treatment are also outlined.

Electrospun Nanofibrous Conduit Filled with a Collagen-Based Matrix (ColM) for Nerve Regeneration.

Traumatic nerve defects result in dysfunctions of sensory and motor nerves and are usually accompanied by pain. Nerve guidance conduits (NGCs) are widely applied to bridge large-gap nerve defects. However, few NGCs can truly replace autologous nerve grafts to achieve comprehensive neural regeneration and function recovery. Herein, a three-dimensional (3D) sponge-filled nanofibrous NGC (sf@NGC) resembling the structure of native peripheral nerves was developed. The conduit was fabricated by electrospinning a poly(L-lactide-co-glycolide) (PLGA) membrane, whereas the intraluminal filler was obtained by freeze-drying a collagen-based matrix (ColM) resembling the extracellular matrix. The effects of the electrospinning process and of the composition of ColM on the physicochemical performance of sf@NGC were investigated in detail. Furthermore, the biocompatibility of the PLGA sheath and ColM were evaluated. The continuous and homogeneous PLGA nanofiber membrane had high porosity and tensile strength. ColM was shown to exhibit an ECM-like architecture characterized by a multistage pore structure and a high porosity level of over 70%. The PLGA sheath and ColM were shown to possess stagewise degradability and good biocompatibility. In conclusion, sf@NGC may have a favorable potential for the treatment of nerve reconstruction.

Engineering Biosensors with Dual Programmable Dynamic Ranges.

Although extensively used in all fields of chemistry, molecular recognition still suffers from a significant limitation: host-guest binding displays a fixed, hyperbolic dose-response curve, which limits its usefulness in many applications. Here we take advantage of the high programmability of DNA chemistry and propose a universal strategy to engineer biorecognition-based sensors with dual programmable dynamic ranges. Using DNA aptamers as our model recognition element and electrochemistry as our readout signal, we first designed a dual signaling "signal-on" and "signal-off" adenosine triphosphate (ATP) sensor composed of a ferrocene-labeled ATP aptamer in complex to a complementary, electrode-bound, methylene-blue labeled DNA. Using this simple "dimeric" sensor, we show that we can easily (1) tune the dynamic range of this dual-signaling sensor through base mutations on the electrode-bound DNA, (2) extend the dynamic range of this sensor by 2 orders of magnitude by using a combination of electrode-bound strands with varying affinity for the aptamers, (3) create an ultrasensitive dual signaling sensor by employing a sequestration strategy in which a nonsignaling, high affinity "depletant" DNA aptamer is added to the sensor surface, and (4) engineer a sensor that simultaneously provides extended and ultrasensitive readouts. These strategies, applicable to a wide range of biosensors and chemical systems, should broaden the application of molecular recognition in various fields of chemistry.

Integrated Solid-State Nanopore Electrochemistry Array for Sensitive, Specific, and Label-Free Biodetection.

Nanopore ionic current measurement is currently a prevailing readout and offers considerable opportunities for bioassays. Extending conventional electrochemistry to nanoscale space, albeit noteworthy, remains challenging. Here, we report a versatile electrochemistry array established on a nanofluidic platform by controllably depositing gold layers on the two outer sides of anodic aluminum oxide (AAO) nanopores, leading to form an electrochemical microdevice capable of performing amperometry in a label-free manner. Electroactive species ferricyanide ions passing through gold-decorated nanopores act as electrochemical indicator to generate electrolytic current signal. The electroactive species flux that dominates current signal response is closely related to the nanopore permeability. Such well-characteristic electrolytic current-species flux correlation lays a premise for quantitative electrochemical analysis. As a proof-of-concept demonstration, we preliminarily verify the analytical utility by detection of nucleic acid and protein at picomolar concentration levels. Universal surface modification and molecule assembly, specific target recognition and reliable signal output in nanopore enable direct electrochemical detection of biomolecules without the need of cumbersome probe labeling and signal amplification.

Fabrication of "Plug and Play" Channels with Dual Responses by Host-Guest Interactions.

The "Plug and Play" template can be individually or successively grafted by dual-responsive molecules on the α-CD modified channels by host-guest interactions and can be peeled off by UV irradiation. The artificial channels present six kinds of responses cycling among four states responding to three environment stimuli, as light, pH, and temperature.

Centrifugation-induced fibrous orientation in fish-sourced collagen matrices.

Orientation of fibrous collagen structures plays an important role not only in the native function of various biological tissues but also in the development of next-generation tissue engineering scaffolds. However, the controlled assembly of collagen in vitro into an anisotropic structure, avoiding complex technical procedures and specialized apparatus, remains a challenge. Here, an oriented collagen matrix was fabricated at the macroscale by simple centrifugation, and the aligned topographical features of the resulting collagen matrix were revealed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and small angle X-ray scattering. The aligned matrix exhibited a higher ultimate tensile strength and strain than a random matrix. Centrifugation had an impact on the diameter and density of the collagen fibrils, while it had no effect on their native D-periodicity and thermal stability. Additionally, structural anisotropy of the collagen matrix facilitated the proliferation and migration of NIH/3T3 fibroblasts, compared with the random one. This simple and cost-effective method could lead to mass production of aligned collagen matrices and future possibilities for different applications in tissue engineering.

A new electrochemical aptasensor based on a dual-signaling strategy and supersandwich assay.

In this study, we develop a new electrochemical aptasensor by coupling two amplification strategies, including a dual signaling strategy and a supersandwich assay. In order to fabricate this aptasensor, a thiolated capture probe (CP) was first self-assembled on the gold electrode surface by Au-S bonds. After the addition of methylene blue (MB) modified signal probe 1 (SP1) and ferrocene (Fc) labeled signal probe 2 (SP2), supersandwich structure DNA, including multiple units of SP1 and SP2, was grown from the CP on the electrode surface. In the presence of ATP, the strong interaction between ATP and its aptamer (CP, SP1) leads to the disassembly of the supersandwich structure and thereby, the release of SP1 and SP2 from the gold electrode surface, resulting in a decrease of the MB and Fc signals. Taking "Signal gainMB + Signal gainFc" as the response signal, ATP can be detected sensitively; the detection limit is 2.1 nM, which is lower than that using either a single-signaling strategy or a traditional sandwich assay alone. Moreover, the new aptasensor also exhibits excellent specificity, selectivity, reliability and applicability. We believe that this new strategy will be helpful for fabricating sensitive and selective electrochemical aptasensors of other biomolecules and small molecules.

Detection of UVA/UVC-induced damage of p53 fragment by rolling circle amplification with AIEgens.

Absorption of ultraviolet (UV) light by nucleic acid could lead to mutations and skin cancers. Traditional damage detection methods based on fluorescence not only need dye/quencher groups but also display relatively high background interference, causing difficulty in synthesis and purification and thus low specificity of detection. Here, by combining rolling circle amplification (RCA) and aggregation-induced emission molecules (AIE), we made up for the defects of traditional methods to some extent and could also differentiate damaged and undamaged DNA. We also studied radiation damage of the p53 gene fragment both from UVA and UVC, although the mechanism of UVA in mutagenesis remains controversial. To amplify the signal-to-background ratio, we ligated the linear p53 (L p53) gene fragment to be a circular p53 (C p53) gene fragment, which is a key component for RCA. The combination of RCA products and positive TPE-Z (quaternized tetraphenylethene salt) molecules induced the aggregation of AIE molecules, and subsequently resulted in significant fluorescence enhancement (the signal for the undamaged DNA is 598% higher than that of the damaged). Compared with the traditional aggregation-caused quenching (ACQ) based fluorescent method, our assay was more sensitive and more specific.

Regulation of DNA self-assembly and DNA hybridization by chiral molecules with corresponding biosensor applications.

Chirality is one of the fundamental biochemical properties in a living system, and a lot of biological and physiological processes are greatly influenced by the chirality of molecules. Inspired by this phenomenon, we study the covalent assembly of DNA on chiral molecule modified surfaces and further discuss the hybridization of DNA on chiral surfaces with nucleic acids. Take methylene blue (MB) modified DNA as a model molecule, we show that the peak current of the L-NIBC (NIBC, N-isobutyryl-L(D)-cysteine) modified gold surface (L-surface) is larger than the D-surface because of a stronger interaction between short-chain DNA and the L-surface; however, the D-surface has a higher hybridization efficiency than the L-surface. Moreover, we apply this result to actual application by choosing an electrochemical DNA (E-DNA) sensor as a potential platform. Furthermore, we further amplify the difference of hybridization efficiency using the supersandwich assay. More importantly, our findings are successfully employed to program the sensitivity and limit of detection.