Stimuli-responsive hydrogel microcapsules for the amplified detection of microRNAs

Autonomous Feedback-Driven Engineered DNAzyme-Coated Trojan Horse-like Nanocapsules for On-Demand CRISPR/Cas9 Delivery

Manipulating the expression of cellular genes through efficient CRISPR/Cas9 delivery is rapidly evolving into a desirable tumor therapeutics. The exposure of CRISPR/Cas9 to a complex external environment poses challenges for conventional delivery carriers in achieving responsive and accurate release. Here, we report a Trojan horse-like nanocapsule for the on-demand delivery of CRISPR/Cas9 in a microRNA-responsive manner, enabling precise tumor therapy. The nanocapsule comprises a nanoassembled, engineered DNAzyme shell encasing a Cas9/sgRNA complex core. The DNAzyme, functioning as a catalytic unit, undergoes a conformational change in the presence of tumor-associated microRNA, followed by activating a positive feedback-driven autonomous catabolic cycle of the nanocapsule shell. This catabolic cycle is accomplished through chain reactions of DNAzyme "cleavage-hybridization-cleavage", which ensures sensitivity in microRNA recognition and effective release of Cas9/sgRNA. Utilizing this Trojan horse-like nanocapsule, as low as 1.7 pM microRNA-21 can trigger the on-demand release of Cas9/sgRNA, enabling the specific editing of the protumorigenic microRNA coding gene. The resulting upregulation of tumor suppressor genes induces apoptosis in tumor cells, leading to significant inhibition of tumor growth by up to 75.94%. The Trojan horse-like nanocapsule, with superior programmability and biocompatibility, is anticipated to serve as a promising carrier for tailoring responsive gene editing systems, achieving enhanced antitumor specificity and efficacy.

Developing hydrogels for gene therapy and tissue engineering

Hydrogels are a class of highly absorbent and easily modified polymer materials suitable for use as slow-release carriers for drugs. Gene therapy is highly specific and can overcome the limitations of traditional tissue engineering techniques and has significant advantages in tissue repair. However, therapeutic genes are often affected by cellular barriers and enzyme sensitivity, and carrier loading of therapeutic genes is essential. Therapeutic gene hydrogels can well overcome these difficulties. Moreover, gene-therapeutic hydrogels have made considerable progress. This review summarizes the recent research on carrier gene hydrogels for the treatment of tissue damage through a summary of the most current research frontiers. We initially introduce the classification of hydrogels and their cross-linking methods, followed by a detailed overview of the types and modifications of therapeutic genes, a detailed discussion on the loading of therapeutic genes in hydrogels and their characterization features, a summary of the design of hydrogels for therapeutic gene release, and an overview of their applications in tissue engineering. Finally, we provide comments and look forward to the shortcomings and future directions of hydrogels for gene therapy. We hope that this article will provide researchers in related fields with more comprehensive and systematic strategies for tissue engineering repair and further promote the development of the field of hydrogels for gene therapy.

Aptamer-Based Switching System for Communication of Non-Interacting Proteins

Biological macromolecules, such as DNA, RNA, and proteins in living organisms, form an intricate network that plays a key role in many biological processes. Many attempts have been made to build new networks by connecting non-communicable proteins with network mediators, especially using antibodies. In this study, we devised an aptamer-based switching system that enables communication between non-interacting proteins. As a proof of concept, two proteins, Cas13a and T7 RNA polymerase (T7 RNAP), were rationally connected using an aptamer that specifically binds to T7 RNAP. The proposed switching system can be modulated in both signal-on and signal-off manners and its responsiveness to the target activator can be controlled by adjusting the reaction time. This study paves the way for the expansion of biological networks by mediating interactions between proteins using aptamers.

Entropy-driven DNA circuit with two-stage strand displacement for elegant and robust detection of miRNA let-7a

MicroRNAs (miRNAs) research in cancer diagnosis is expanding, on account of miRNAs were demonstrated to be key indicator of gene expression and hopeful candidates for biomarkers. In this study, a stable miRNA-let-7a fluorescent biosensor was successfully designed based on an exonuclease Ⅲ-assisted two-stage strand displacement reaction (SDR). First, an entropy-driven SDR containing a three-chain structure of the substrate is used in our designed biosensor, leading to reduce the reversibility of the target recycling process in each step. The target acts on the first stage to start the entropy-driven SDR, which generates the trigger used to stimulate the exonuclease Ⅲ-assisted SDR in the second stage. At the same time, we design a SDR one-step amplification strategy as a comparison. Expectly, this developed two-stage strand displacement system has a low detection limit of 25.0 pM as well as a broad detection range of 4 orders of magnitude, making it more sensitive than the SDR one-step sensor, whose detection limit is 0.8 nM. In addition, this sensor has high specificity across members of the miRNA family. Therefore, we can take advantage of this biosensor to promote miRNA research in cancer diagnosis sensing systems.

Quantification of Multiplex miRNAs by Mass Spectrometry with Duplex-Specific Nuclease-Mediated Amplification

Early quantification of multiplex biomarkers such as microRNAs (miRNAs) is critical during disease pathologic development and therapy. To tackle challenges of low abundance and multiplexing, we herein report a mass-encoded biosensing approach with duplex-specific nuclease (DSN) mediated signal amplification. Magnetic Fe3O4 cores are coated with small gold nanoparticles (AuNPs), which are applied to achieve facile DNA immobilization subsequent separation. This biosensor integrates multiple mass reporters corresponding to different targets (five miRNAs as examples). Due to the excellent resolution of mass spectrometry, these targets can be successfully distinguished in a single spectrum. Wide detection ranges from 10 fM to 1 nM are achieved, and the limits of detection are estimated to be 10 fM. High selectivity is promised due to the enzyme activity of DSN, and practical application in human serum samples performs satisfactorily. The number of targets to be tested can be further expanded by designing different specific mass tags in theory. Therefore, the proposed method can be utilized as an important and valuable tool to quantify multiplex miRNAs for disease screening as well as biomedical investigations.

DNA hydrogels and nanogels for diagnostics, therapeutics, and theragnostics of various cancers

As an efficient class of hydrogel-based therapeutic drug delivery systems, deoxyribonucleic acid (DNA) hydrogels (particularly DNA nanogels) have attracted massive attention in the last five years. The main contributor to this is the programmability of these 3-dimensional (3D) scaffolds that creates fundamental effects, especially in treating cancer diseases. Like other active biological ingredients (ABIs), DNA hydrogels can be functionalized with other active agents that play a role in targeting drug delivery and modifying the half-life of the therapeutic cargoes in the body's internal environment. Considering the brilliant advantages of DNA hydrogels, in this survey, we intend to submit an informative collection of feasible methods for the design and preparation of DNA hydrogels and nanogels, and the responsivity of the immune system to these therapeutic cargoes. Moreover, the interactions of DNA hydrogels with cancer biomarkers are discussed in this account. Theragnostic DNA nanogels as an advanced species for both detection and therapeutic purposes are also briefly reviewed.

Recent Advances in Stimuli-Responsive Hydrogel-Based Wound Dressing

Polymeric materials have found increasing use in biomedical applications in the last decades. Among them, hydrogels represent the chosen class of materials to use in this field, in particular as wound dressings. They are generally non-toxic, biocompatible, and biodegradable, and they can absorb large amounts of exudates. Moreover, hydrogels actively contribute to skin repair promoting fibroblast proliferation and keratinocyte migration, allowing oxygen to permeate, and protecting wounds from microbial invasion. As wound dressing, stimuli-responsive systems are particularly advantageous since they can be active only in response to specific environmental stimuli (such as pH, light, ROS concentration, temperature, and glucose level). In this review, we briefly resume the human skin's structure and functions, as well as the wound healing phases; then, we present recent advances in stimuli-responsive hydrogels-based wound dressings. Lastly, we provide a bibliometric analysis of knowledge produced in the field.

Single-atom catalysts with peroxidase-like activity boost gel-sol transition-based biosensing

Gel-sol transition-based biosensors are a promising and popular alternative for portable, cost-effective, and user-friendly point-of-care testing (POCT). However, the improvement of sensitivity and practicability is highly demanded. In this work, a Fe-NC single-atom catalyst (SAC) is successfully synthesized and used as a signal amplification element for highly sensitive gel-sol transition-based biosensing. The Fe-NC SAC owns excellent peroxidase-like activity of 188 U/mg due to its definite atomically active centers and maximum atomic utilization of active metal atoms. As a proof-of-concept, the Fe-NC SAC is uniformly encapsulated in gelatin hydrogel to obtain a hydrogel sensor that allows colorimetric detection of trypsin based on gel-sol transition. The gelatin hydrogel network collapses derived from the hydrolysis by trypsin, and thereby the released Fe-NC SAC leads to the colorimetric sensing process. The designed hydrogel sensor offers a low detection limit of 1 ng/mL with a range from 1 to 100 ng/mL toward trypsin detection, exhibiting excellent selectivity and sensitivity, and well-performed practical detection in human serum. This work offers a successful paradigm for designing a promising SACs-related detection strategy and paves a new way to develop high-performance gel-sol transition-based sensors and various POCT applications.

Stimulus-Responsive DNA Hydrogel Biosensors for Food Safety Detection

Food safety has always been a major global challenge to human health and the effective detection of harmful substances in food can reduce the risk to human health. However, the food industry has been plagued by a lack of effective and sensitive safety monitoring methods due to the tension between the cost and effectiveness of monitoring. DNA-based hydrogels combine the advantages of biocompatibility, programmability, the molecular recognition of DNA molecules, and the hydrophilicity of hydrogels, making them a hotspot in the research field of new nanomaterials. The stimulus response property greatly broadens the function and application range of DNA hydrogel. In recent years, DNA hydrogels based on stimulus-responsive mechanisms have been widely applied in the field of biosensing for the detection of a variety of target substances, including various food contaminants. In this review, we describe the recent advances in the preparation of stimuli-responsive DNA hydrogels, highlighting the progress of its application in food safety detection. Finally, we also discuss the challenges and future application of stimulus-responsive DNA hydrogels.

DNA-Tetrahedra Corona-Modified Hydrogel Microcapsules: "Smart" ATP- or microRNA-Responsive Drug Carriers

The assembly of adenosine triphosphate (ATP)-responsive and miRNA-responsive DNA tetrahedra-functionalized carboxymethyl cellulose hydrogel microcapsules is presented. The microcapsules are loaded with the doxorubicin-dextran drug or with CdSe/ZnS quantum dots as a drug model. Selective unlocking of the respective microcapsules and the release of the loads in the presence of ATP or miRNA-141 are demonstrated. Functionalization of the hydrogel microcapsules a with corona of DNA tetrahedra nanostructures yields microcarriers that revealed superior permeation into cells. This is demonstrated by the effective permeation of the DNA tetrahedra-functionalized microcapsules into MDA-MB-231 breast cancer cells, as compared to epithelial MCF-10A nonmalignant breast cells. The superior permeation of the tetrahedra-functionalized microcapsules into MDA-MB-231 breast cancer cells, as compared to analog control hydrogel microcapsules modified with a corona of nucleic acid duplexes. The effective permeation of the stimuli-responsive, drug-loaded, DNA tetrahedra-modified microcapsules yields drug carriers of superior and selective cytotoxicity toward cancer cells.

Design and application of stimuli-responsive DNA hydrogels: A review

Deoxyribonucleic acid (DNA) hydrogels combine the properties of DNAs and hydrogels, and adding functionalized DNAs is key to the wide application of DNA hydrogels. In stimuli-responsive DNA hydrogels, the DNA transcends its application in genetics and bridges the gap between different fields. Specifically, the DNA acts as both an information carrier and a bridge in constructing DNA hydrogels. The programmability and biocompatibility of DNA hydrogel make it change macroscopically in response to a variety of stimuli. In order to meet the needs of different scenarios, DNA hydrogels were also designed into microcapsules, beads, membranes, microneedle patches, and other forms. In this study, the stimuli were classified into single biological and non-biological stimuli and composite stimuli. Stimuli-responsive DNA hydrogels from the past five years were summarized, including but not limited to their design and application, in particular logic gate pathways and signal amplification mechanisms. Stimuli-responsive DNA hydrogels have been applied to fields such as sensing, nanorobots, information carriers, controlled drug release, and disease treatment. Different potential applications and the developmental pro-spects of stimuli-responsive DNA hydrogels were discussed.

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DNA hydrogel, favored by researchers, combines properties of DNA and hydrogels.

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Both DNA and skeleton, having many response characteristics, can respond to stimuli.

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Sensing, nano robots, information carriers, drug delivery, and disease treatment uses.

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Three stimulus response types: single biological, single abiotic and compound.

A Multiple-Stimuli-Responsive Amphiphilic Copolymer for Antifouling and Antibacterial Functionality via a “Resistance–Kill–Release” Mechanism

In recent years, polymers with stimuli-responsive properties have been increasingly reported on due to their diverse applications. However, most of the studies have only focused on the performance of polymers under specific scenarios. The laws of changes in the properties in response to various external stimuli have been less systematically and quantitatively studied. In this paper, we prepared an amphiphilic polymer (PadaMX and PAdaM3QA−X) with temperature-, pH-, ion-, and β-cyclodextrin (β-CD)-responsive properties. According to the cloud point tested by the UV-Vis method, the lower critical soluble temperature (LCST) of PAdaM3QA−10% was more sensitive to a change in pH and less sensitive to a change in ions compared with PadaM3 due to quaternized side chains with a stronger intramolecular mutual repulsion. We then fabricated the coatings with responsive properties by immobilizing the adamantyl groups on β-CD-modified surfaces. The hydrophilicity of the coatings was improved after quaternization, as proven by the water contact angle (WCA) measurement. The antifouling and antibacterial performance was further evaluated via the fluorescence intensity of bovine serum albumin (BSA) adsorbed on the surfaces and the spread plate method. A 78.4% BSA desorption rate and a 96.8% sterilization rate were achieved by the PAdaM3QA−10% coating. In summary, this work prepared a multiple-stimuli-responsive amphiphilic copolymer for antifouling and antibacterial functionality via a “resistance–kill–release” mechanism.

A novel electrochemical biosensor based on MIL-101-NH2 (Cr) combining target-responsive releasing and self-catalysis strategy for p53 detection

A novel electrochemical biosensor was constructed to detect p53 gene based on MIL-101-NH₂ (Cr) by combining target-responsive releasing and self-catalysis strategy. MIL-101-NH₂ (Cr) with suitable pore structure was used to encapsulate methylene blue (MB) as signal probe. The hairpin DNA (HP) containing rich-G sequences was used as gatekeeper to seal up the pores and avoid MB leakage through covalent immobilization. The p53 gene could hybridize with the loop portion of HP for the formation of dsDNA, which had the specific nicking site of the nicking endonuclease (Nt.BstNBI). Then Nt.BstNBI recognized the specific recognition site and cleaved HP to open the pore for releasing of MB. Meanwhile, the cleavage of HP released the target DNA to trigger the target recycling for signal amplification. More importantly, the plentiful rich-G sequences were exposed to form Hemin/G-quadruplex DNAzymes, which could unite MIL-101-NH₂ (Cr) to catalyze redox reaction of MB released by itself for signal amplification. The biosensor for p53 had wide linear range from 1 × 10^-14 to 1 × 10^-7 M and a low detection limit of 1.4 × 10^-15 M. The combination of target-responsive releasing and self-catalysis strategy provided a promising way for constructing ultrasensitive and simple biosensor.

Advances and prospects of dynamic DNA nanostructures in biomedical applications

With the rapid development of DNA nanotechnology, the emergence of stimulus-responsive dynamic DNA nanostructures (DDNs) has broken many limitations of static DNA nanostructures, making precise, remote, and reversible control possible. DDNs are intelligent nanostructures with certain dynamic behaviors that are capable of responding to specific stimuli. The responsible stimuli of DDNs include exogenous metal ions, light, pH, etc., as well as endogenous small molecules such as GSH, ATP, etc. Due to the excellent stimulus responsiveness and other superior physiological characteristics of DDNs, they are now widely used in biomedical fields. For example, they can be applied in the fields of biosensing and bioimaging, which are able to detect biomarkers with greater spatial and temporal precision to help disease diagnosis and live cell physiological function studies. Moreover, they are excellent intelligent carriers for drug delivery in treating cancer and other diseases, achieving controlled release of drugs. And they can promote tissue regeneration and regulate cellular behaviors. Although some challenges need further study, such as the practical value in clinical applications, DDNs have shown great potential applications in the biomedical field.

With the rapid development of DNA nanotechnology, the emergence of stimulus-responsive dynamic DNA nanostructures (DDNs) has great potential applications in the biomedical field.

Biocatalytic cascades and intercommunicated biocatalytic cascades in microcapsule systems

Dynamic dimerization of GOx-loaded microcapsules with β-gal//hemin/G-quadruplex-bridged T1/T2-loaded microcapsules guides the bi-directional intercommunication of the three catalysts cascade.