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.

Nanopore-based DNA-probe sequence-evolution method unveiling characteristics of protein-DNA binding phenomena in a nanoscale confined space.

Almost all of the important functions of DNA are realized by proteins which interact with specific DNA, which actually happens in a limited space. However, most of the studies about the protein-DNA binding are in an unconfined space. Here, we propose a new method, nanopore-based DNA-probe sequence-evolution (NDPSE), which includes up to 6 different DNA-probe systems successively designed in a nanoscale confined space which unveil the more realistic characteristics of protein-DNA binding phenomena. There are several features; for example, first, the edge-hindrance and core-hindrance contribute differently for the binding events, and second, there is an equilibrium between protein-DNA binding and DNA-DNA hybridization.

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.

Ultrahigh pressure field: A friendly pathway for regulating the cellular adhesion and migration capacity of collagen.

Customized control of the biological response between the material matrix and cells is a crucial aspect in the development of the next generation of collagen materials. This study aims to investigate the effects of ultrahigh pressure treatment on the interaction between collagen and cells by subjecting bovine tendon collagen to different intensities of ultrahigh pressure field. The results indicate that ultrahigh pressure treatment alters the spatial folding of collagen, causing distortion of its triple helical conformation and exposing more free amino groups and hydrophobic regions. As a result, collagen's cell adhesion capability and ability to promote cell migration are significantly enhanced. Optimal cell adhesion and migration capabilities are observed in collagen samples treated at 500 MPa for 15 min. However, further increasing the intensity of the ultrahigh pressure treatment leads to severe damage to the triple-helical structure of collagen, along with re-aggregation of free amino groups and hydrophobic moieties, thereby reducing collagen's cell adhesion capability and ability to promote cell migration. Therefore, ultrahigh pressure treatment offers a promising method to effectively regulate collagen-cell adhesion and promote cell migration without the need for external components. This provides a potential means for the customized enhancement of collagen-based material interfaces.

Mesenchymal Stem Cell Derived Extracellular Vesicles: Promising Nanomedicine for Cutaneous Wound Treatment.

A skin wound represents a rupture caused by external damage or the existence of underlying pathological conditions. Sometimes, skin wound healing processes may place a heavy burden on patients, families, and society. Wound healing processes mainly consist of several continuous, dynamic, but overlapping stages, namely, the coagulation stage, inflammation stage, proliferation stage, and remodeling stage. Bacterial infection, excessive inflammation, impaired angiogenesis, and scar formation constitute the four significant factors impeding the recovery efficacy of skin wounds. This encourages scientists to develop multifunctional nanomedicines to meet challenging needs. As we know, mesenchymal stem cells (MSCs) have been widely explored for wound repair owing to their unique capability for self-renewal and multipotency. However, problems including immune concerns and legal restrictions should be properly resolved before MSC-based therapeutics are safely and widely used in clinics. Besides, maintaining the high viability/proliferation capability of MSCs during administration processes and therapy procedures is also one of the biggest technical bottlenecks. Extracellular vesicles (EVs) are cell-derived nanovesicles, that not only possess the basic characteristics and functions of their corresponding maternal cells but also contain several outstanding advantages including abundant sources, excellent biocompatibility, and convenient administration routes. Furthermore, the membrane surface and cavity are easy to flexibly modify to meet versatile application needs. Recently, MSC-derived EVs have emerged as promising therapeutics for skin wound repair. However, current reviews are too broad and rarely focused on the specific roles of EVs in the different stages of wound recovery. Therefore, it is quite necessary to demonstrate the significance of stem cell-derived EVs in promoting wound healing from several specific aspects. Here, this review primarily tries to provide critical comments on current advances in EVs derived from MSCs for wound repair, particularly elaborating on their impressive roles in effectively eliminating infections, inhibiting inflammation, promoting angiogenesis, and reducing scar formation. Last but not least, current limitations and future prospects of EVs derived from MSCs in the areas of wound repair are also objectively analyzed.

Insight into the differences in carbon dots prepared from fish scales using conventional hydrothermal and microwave methods.

The preparation of carbon dots (CDs) from waste fish scales is an attractive and high-value transformation. In this study, fish scales were used as a precursor to prepare CDs, and the effects of hydrothermal and microwave methods on their fluorescence properties and structures were evaluated. The microwave method was more conducive to the self-doping of nitrogen due to rapid and uniform heating. However, the low temperature associated with the microwave method resulted in insufficient dissolution of the organic matter in the fish scales, resulting in incomplete dehydration and condensation and the formation of nanosheet-like CDs, whose emission behavior had no significant correlation with excitation. Although the CDs prepared using the conventional hydrothermal method showed lower nitrogen doping, the relative pyrrolic nitrogen content was higher, which was beneficial in improving their quantum yield. Additionally, the controllable high temperature and sealed environment used in the conventional hydrothermal method promoted dehydration and condensation of the organic matter in the fish scales to form CDs with a higher degree of carbonization, uniform size, and higher C = O/COOH content. CDs prepared using the conventional hydrothermal method exhibited higher quantum yields and excitation wavelength-dependent emission behavior.

Site-specific modification of N-terminal α-amino groups of succinylated collagen.

Polymer based protein engineering provides an attractive strategy to endow novel properties to protein and overcome the inherent limitations of both counterparts. The exquisite control of site and density of attached polymers on the proteins is crucial for the bioactivities and properties of the protein-polymer bioconjugates, but is still a challenge. Collagen is the major structural protein in extracellular matrix of animals. Based on the advancements of polymer-based protein engineering, collagen bioconjugates has been widely fabricated and applied as biomaterials. However, the site-specific synthesis of well-defined collagen-polymer bioconjugates is still not achieved. Herein, a versatile strategy for the specific modification of N-terminal α-amino groups in collagen was developed. Firstly, all reactive amino groups of tropocollagen (collagen with telopeptides) were protected by succinic anhydride. Then, the telopeptides were digested to give the active N-terminal α-amino groups, which were subsequently attached with poly(N-isopropylacrylamide) (PNIPAAm) via "grafting from" method based on the atom transfer radical polymerization (ATRP). The site-specific N-terminal PNIPAAm modified succinylated collagen was prepared and its structure, thermal responsive behaviour, and properties was explored.

A fluorescent sensing platform based on collagen peptides-protected Au/Ag nanoclusters and WS2 for determining collagen triple helix integrity.

The unique triple helix structure of collagen plays an important role in its biological properties, and the triple helix integrity is closely correlated with its molecular behavior and biological functions. Nevertheless, there is still a lack of convenient, accurate and practical methods for quantitatively determining collagen triple helix integrity. Herein, we first prepared bovine skin collagen peptide (BSCP)-protected Au/Ag nanoclusters (Au/AgNCs@BSCP) with excellent optical properties, high stability and good biocompatibility, which could adsorb on WS2 surface leading to fluorescence quenching. Upon the addition of collagen, the interaction of collagen and Au/AgNCs@BSCP led to the detachment of Au/AgNCs@BSCP from the WS2 surface, causing an increase in the fluorescence signal. Using the difference in the fluorescence recovery of the different samples, we achieved the quantitative determination of collagen triple helix integrity. This developed strategy exhibited excellent accuracy, selectivity, and practicality, thus showing promising potentials in biomedical applications.

Fabrication of a stepwise degradable hybrid bioscaffold based on the natural and partially denatured collagen.

As a major component of extracellular matrixes (ECMs), collagen is an attractive biomaterial to fabricate porous scaffold for tissue engineering due to their similarity to the in vivo static microenvironment. However, the collagen-based porous scaffolds were difficult to mimic the dynamically remolded porous structure of ECM during the cell proliferation and tissue development, and always have poor mechanical property and not easy to handle. Here, natural collagen and partially denatured collagen was used to prepare the stepwise degradable hybrid bioscaffold with suitable mechanical property and dynamically remolded inner porous structure, which is desirable for the applications of tissue engineering. The collagen-based microporous scaffold was first prepared and used as physical support, then, the mechanical strength of which was reinforced by the import of the partially denatured collagen to give the hybrid bioscaffold. The fabrication conditions of the hybrid scaffolds were optimized, of which the thermal stability, mechanical property, and swelling property was explored. The stepwise enzymatic degradation process and the corresponding porous structure variation of the hybrid scaffold was confirmed by SEM and cell culture assays.

Facile preparation of a collagen-graphene oxide composite: A sensitive and robust electrochemical aptasensor for determining dopamine in biological samples.

A sensitive and robust electrochemical aptasensor for determining dopamine (DA) was developed using a grass carp skin collagen-graphene oxide (GCSC-GO) composite as a transducer and a label-free aptamer as a biological recognition element for the first time. In order to fabricate this sensor, the GCSC-GO composite was firstly prepared by ultra-sonication method and characterized by atomic force microscope, infrared spectroscopy, Raman spectroscopy, and electrochemical impedance spectroscopy. Subsequently, a label-free DA-binding aptamer was immobilized through strong interaction between collagen and aptamer. The fabricated electrochemical aptasensor was used to determine DA by differential pulse voltammetry. The results indicated that the peak current changes of the developed aptasensor was linear relationship with the DA concentrations from 1 to 1000 nM, and the detection limit was 0.75 nM (S/N = 3). Moreover, the fabricated aptasensor showed high selectivity for DA. More importantly, the obtained aptasensor exhibited satisfactory recovery toward DA in human serum specimens with excellent stability.

Insight into the role of grafting density in the self-assembly of acrylic acid-grafted-collagen.

Side chain modification of collagen provides an attractive way to enhance their structure and functions, which is highly desirable for the development of promising biomaterials. However, the impact of structural change of side chains on the intrinsic self-assembly property of collagen was always ignored. Here, a series of acrylic acid-grafted-collagen (AA-g-Col) with different grafting density were prepared to explore the impact of side chain structural variation on the self-assembly of collagen. The results showed that excessive grafting density would weaken or even disappear the self-assembly property of AA-g-Col, but only affects the triple helix to a minor extent. Compared to pristine collagen, the mechanical property and cytocompatibility of AA-g-Col based matrices also deteriorated, along with the increase of grafting density. Therefore, this work contributed a new insight into the importance of grafting density for the study of modified collagen, which would be helpful for the design of optimized formulate collagen-based hybrid materials with both additional novel functions and tissue-mimicking fibrillary structures.

Effect of ultra-high pressure on molecular structure and properties of bullfrog skin collagen.

Ultra-high pressure technology has attracted a great deal of attention in recent years, and has been widely used in food science, medicine, and other fields. This study aimed to determine the effect of ultra-high pressure on the structure and properties of collagen. Native collagen extracted from bullfrog skin was processed under different ultra-high pressure treatment conditions (300, 400, and 500MPa). Then systematic analysis of the molecular structures and properties of the samples after ultra-high pressure treatment were performed. It was found that the conformation of collagen molecules could be adjusted by ultra-high pressure treatment, and this regulation was closely related to the level of treatment pressure. A possible mechanism of the impact of ultra-high pressure on the collagen molecular structures was speculated according to the experimental results. At low pressure levels (300-400MPa), the pressure perpendicular to collagen axis dominates and leads to a tightening of the triple helix structure of collagen, while the pressure parallel to collagen axis is dominant and the triple helix tends to dissociate like a zipper at high pressure levels (>400MPa). These structural changes would simultaneously result in various changes to thermal stability, self-assembly properties, and antigenicity of collagen.