Advances in i-motif structures: Stability, gene expression, and therapeutic applications

The i-motif, a cytosine-rich DNA structure formed under acidic conditions, plays a pivotal role in regulating gene expression and holds significant therapeutic potential across various diseases. Found in the promoter regions of oncogenes such as Bcl-2, C-MYC, and KRAS, i-motifs dynamically interact with transcription factors and ligands to modulate oncogene activity. Their pH-sensitive nature enables innovative applications, including cellular pH sensors like the "i-switch" and drug delivery platforms such as DNA hydrogels that release therapeutics in acidic tumor microenvironments. However, challenges remain in developing specific ligands and detection methods. Advances in nanotechnology and multi-target therapies highlight the transformative potential of i-motifs in precision medicine. This review underscores the importance of i-motifs as therapeutic targets and tools, bridging fundamental research with clinical applications in oncology, metabolic disorders, and neurodegenerative diseases.

Directional Macrocycle Transport, Release, and Recapture Enabled by a Rotaxane Transporter

A transporter for a directional macrocycle transport, release, and recapture was constructed. This was achieved using a rotaxane featuring a dibenzo-24-crown-8 macrocycle, dibenzylammonium (DBA)/methyl triazolium (MTA) stations on the thread and anthracene/triisopropylsilyl-acetylene stoppers, respectively. In the protonated rotaxane, the macrocycle primarily resides on the DBA station, followed by directional shuttling to the MTA station upon treatment with base. Addition of fluoride as an additional chemical input cleaves the triisopropylsilyl stopper, leading to release of the macrocycle and the half-thread into solution. The released macrocycle can be recaptured by protonation, and the mechanical bond can be reestablished via CuAAC click reaction, enabled by the terminal acetylene unit on the half-thread. This generates an elongated second-generation rotaxane transporter, which was used for a second cycle of directional macrocycle transport and release, proving the possibility of an iterative operation of the rotaxane-transporter in this molecular design.

pH/glutathione dual-responsive copper sulfide-coated organic mesoporous silica for synergistic chemo-photothermal therapy

Nanodrug delivery systems (NDSs), such as mesoporous silica, have been widely studied because of their high specific surface area, high loading rate, and easy modification; however, they are not easily metabolized and excreted by the human body and may be potentially harmful. Hence, we aimed to examine the synergistic anti-tumor effects of ex vivo chemo-photothermal therapy to develop a rational and highly biocompatible treatment protocol for tumors. We constructed a biodegradable NDS using organic mesoporous silica with a tetrasulfide bond structure, copper sulfide core, and folic acid-modified surface (CuS@DMONs-FA-DOX-PEG) to target a tumor site, dissociate, and release the drug. The degradation ability, photothermal conversion ability, hemocompatibility, and in vitro and in vivo anti-tumor effects of the CuS@DMONs-FA-DOX-PEG nanoparticles were evaluated. Our findings revealed that the nanoparticles encapsulated in copper sulfide exhibited significant photothermal activity and optimal photothermal conversion rate. Further, the drug was accurately delivered and released into the target tumor cells, annihilating them. This study demonstrated the successful preparation, safety, and synergistic anti-tumor effects of chemo-photothermal therapeutic nanomaterials.

Type-I heterojunction destruction by In situ formation of Bi2S3 for split-type photoelectrochemical aptasensor

Development of new strategies in photoelectrochemical (PEC) sensors is an important way to realize sensitive detection of biomolecule. In this study, mesoporous silica nanospheres (MSNs)-assisted split-type PEC aptasensor with in situ generation of Bi₂S₃ was proposed to achieve reliable detection of prostate-specific antigen (PSA). To be more specific, this bioresponsive release system will release large amounts of Na₂S by the reaction between PSA and aptamer that capped Na₂S-loading MSNs. Next, the Na₂S reacts with Bi to yield BiOI/BiOBr/Bi₂S₃ composite, which leads to an alteration in the electron-hole transfer pathway of the photoelectric material and a decrease in the response. As the PSA concentration increases, more Na₂S can be released and lower photocurrent is obtained. The linear range under the optimal experimental conditions is 10 pg·mL^-1-1 μg⋅mL^-1, and the detection limit is 1.23 pg⋅mL^-1, which has satisfactory stability and anti-interference.

Exploiting recent trends for the synthesis and surface functionalization of mesoporous silica nanoparticles towards biomedical applications

Rapid progress in developing multifunctional nanocarriers for drug delivery has been observed in recent years. Inorganic mesoporous silica nanocarriers (MSNs), emerged as an ideal candidate for gene/drug delivery with distinctive morphological features. These ordered carriers of porous nature have gained unique attention due to their distinctive features. Moreover, transformation can be made to these nanocarriers in terms of pores size, pores volume, and particle size by altering specific parameters during synthesis. These ordered porous materials have earned special attention as a drug carrier for treating multiple diseases. Herein, we highlight the strategies employed in synthesizing and functionalizing these versatile nanocarriers. In addition, the various factors that influence their sizes and morphological features were also discussed. The article also summarizes the recent advancements and strategies for drug and gene delivery by rendering smarter MSNs by incorporating functional groups on their surfaces. Averting off-target effects through various capping strategies is a massive milestone for the induction of stimuli-responsive nanocarriers that brings out a great revolution in the biomedical field.

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MSNs serve as an ideal candidate for gene/drug delivery with unique and excellent attributes.

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MSNs surface can be functionalized using specific materials to impart unique structural features.

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Functionalization of MSNs with stimuli-responsive molecules can act as gatekeepers by responding to the desired stimulus after uncapping.

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These capping agents act as vital targeting agents in developing MSNs being employed in various biomedical applications.

A review on the latest developments of mesoporous silica nanoparticles as a promising platform for diagnosis and treatment of cancer

Cancer is the second cause of human mortality after cardiovascular disease around the globe. Conventional cancer therapies are chemotherapy, radiation, and surgery. In fact, due to the lack of absolute specificity and high drug concentrations, early recognition and treatment of cancer with conventional approaches have become challenging issues in the world. To mitigate against the limitations of conventional cancer chemotherapy, nanomaterials have been developed. Nanomaterials exhibit particular properties that can overcome the drawbacks of conventional therapies such as lack of specificity, high drug concentrations, and adverse drug reactions. Among nanocarriers, mesoporous silica nanoparticles (MSNs) have gained increasing attention due to their well-defined pore size and structure, high surface area, good biocompatibility and biodegradability, ease of surface modification, and stable aqueous dispersions. This review highlights the current progress with the use of MSNs for the delivery of chemotherapeutic agents for the diagnosis and treatment of cancer. Various stimuli-responsive gatekeepers, which endow the MSNs with on-demand drug delivery, surface modification strategies for targeting purposes, and multifunctional MSNs utilized in drug delivery systems (DDSs) are also addressed. Also, the capability of MSNs as flexible imaging platforms is considered. In addition, physicochemical attributes of MSNs and their effects on cancer therapy with a particular focus on recent studies is emphasized. Moreover, major challenges to the use of MSNs for cancer therapy, biosafety and cytotoxicity aspects of MSNs are discussed.

Preparation of RGD Peptide/Folate Acid Double-Targeted Mesoporous Silica Nanoparticles and Its Application in Human Breast Cancer MCF-7 Cells

Pharmacological Relevance

Paclitaxel (PTX) is currently the only botanical drug that can control the growth of cancer cells. Paclitaxel is widely used in the treatment of breast cancer, ovarian cancer, uterine cancer, non-small cell lung cancer and other cancers.

Aim

Folate receptor and integrin α _v β ₃ are highly expressed on the surface of human breast cancer cells MCF-7. Folic acid and arginine-glycine-aspartate (Arg-Gly-Asp, RGD) tripeptide sequence have a high affinity for folate receptor and integrin α _v β ₃, respectively. To enhance the effect on breast cancer, we constructed the folate acid and RGD peptide dual-targeted (MSNs-NH₂-FA-RGD) drug-carrier based on mesoporous silica nanoparticles.

Methods

The structure of mesoporous nanocarriers was characterized by Fourier transform infrared spectroscopy, nitrogen adsorption-desorption analysis, transmission electron microscopy, laser particle size analyzer, and thermogravimetric analysis. Paclitaxel was chosen as the model drug. The targeting-ability was verified by observing the uptake of mesoporous carriers loaded with rhodamine in MCF-7, MCF-10A, and HeLa cells using a fluorescence microscope. The cytotoxicity of the blank carrier MSNs-NH₂-FA-RGD and the efficacy of the drug carrier PTX@MSNs-NH₂-FA-RGD were assessed by cell experiments.

Results

The characterization showed successful construction of a dual-targeted mesoporous silica nanocarrier. Obvious differences were detected in the fluorescence intensity of the three cell lines. The results of the pharmacological tests indicated that the blank nanoparticles do not cause any apparent toxicity on these cells. The IC₅₀ of free PTX and PTX@MSNs-NH₂-FA-RGD on MCF-7 cells line treated for 48 h were 35.25±2.57 ng·ml^-1 and 22.21±3.4 ng·ml^-1 respectively, which indicated that the inhibitory efficacy of PTX@MSNs-NH₂-FA-RGD on MCF-7 was 1.6 times than that of free PTX.

Conclusions

The dual-targeted nanocarrier MSNs-NH₂-FA-RGD could target breast cancer cells, and sever as a potential candidate in future of drug development.

Synthesis and biological evaluation of redox/NIR dual stimulus-responsive polymeric nanoparticles for targeted delivery of cisplatin

Functional drug delivery systems enabling various favorable characteristics including specific targets, efficient cellular uptake and controllable release. At present work, a folate and cRGD dual modified nanoparticles based on NIR light and glutathione dual stimuli-responsive release system was successfully prepared and which simultaneously deliver cisplatin and ICG to tumor sites to enhance controllability. The prepared nanoparticles showed a stable uniform spherical morphology of 77.59 nm particle size range in PBS (pH = 7.4, 25 °C) and the encapsulated cisplatin were rapidly released in acidic environment especially added glutathione (GSH) and NIR irradiation. Moreover, the prepared nanoparticles can be efficiently internalized by tumor cells through the enhanced dual targeted ligands (folate and cRGD) for ICG imaging. The cytotoxicity assays showed that the cells viability decreased to 1.95% (SGC-7901) when been exposed to NIR light, and which further decreased to 1.25% in MCF-7 cells. Thus, the prepared nanoparticles showed excellent performance for photothermal conversion therapy of tumor cells and especially on human breast tumor cells. Our research highlights the great potential of stimuli-responsive smart nanoparticles in biomaterial and nano-biomedicine.

Mesoporous Silica Nanoparticles as Carriers for Intracellular Delivery of Nucleic Acids and Subsequent Therapeutic Applications

Nucleic acids, including DNA, microRNA (miRNA), small interfering RNA (siRNA), and antisense oligonucleotide (ASO), are powerful gene regulators, which have been demonstrated as promising drug candidates for therapeutic treatments. Nevertheless, poor cellular membrane permeability and serum stability have greatly hindered the applications of nucleic acids in biomedicine. To address these issues, associate carriers that can encapsulate and protect nucleic acids are urgently required. Mesoporous silica nanoparticles (MSNs or MSNPs), which are nanomaterials with excellent biocompatibility, large surface area for functionalization, and tunable pore size for encapsulating different cargos, are emerging as novel and ideal biomaterials for different biomedical applications. In this review paper, we focus on the applications of MSNs in nucleic acid delivery and nucleic acid-guided therapeutic treatments. General strategies for the preparation of nucleic acid-MSN complexes will be firstly introduced, followed by a summary of recent applications of MSNs in nucleic acid delivery and nucleic acid-guided therapeutics.

Composite of functional mesoporous silica and DNA: an enzyme-responsive controlled release drug carrier system

An efficient enzyme-responsive controlled release carrier system was successfully fabricated using single-stranded DNA encapsulated functional mesoporous silica nanoparticles. Mesoporous silica nanoparticles were initially fabricated through hydrolysis of tetraethyl orthosilicate (TEOS) in cetyltrimethylammonium chloride (CTAC) solution, and the surface of nanoparticles could be encapsulated with single-stranded DNA. This nanomaterial has excellent bioactivity and its hydrolysate cannot cause damage to normal cell, thus the biocompatibility of the nanomaterial is improved. In addition, this nanomaterial showed an excellent drug release performance when loaded with drugs, which would be helpful to increase the treatment efficiency and decrease side effects of drugs.

A pH-responsive polymer/mesoporous silica nano-container linked through an acid cleavable linker for intracellular controlled release and tumor therapy in vivo

This paper proposes a pH-responsive polymer/mesoporous silica nano-container linked through an acid cleavable linker for intracellular controlled release and tumor therapy in vivo. In this system, the poly(acrylic acid) homopolymer (PAA), as a nanoscopic cap, is grafted onto the MSN through an acid cleavable linker (PAA-ACL-MSN). Doxorubicin (DOX), as a model drug, is used to assess the drug release behaviors and tumor therapy. At neutral pH, the linker is intact, resulting in blockage of pores and package of DOX. By the degradation of the linker at acidic pH, the grafted PAA is removed, which gives rise to uncapping and the subsequent pH-responsive controlled release of DOX. In vitro studies using a nasopharyngeal carcinoma cell line (HNE-1) prove that DOX loaded PAA-ACL-MSN (DOX@PAA-ACL-MSN) is endocytosed and demonstrates efficient operation at lysosomal pH, leading to significant cytotoxicity. As a preliminary tumor therapy in vivo, the progressive tumor development and inhibition following DOX@PAA-ACL-MSN treatment is monitored using bioluminescence imaging. By the examination of cell proliferation in tumor tissues and the comparison of body weight, it is revealed that the DOX@PAA-ACL-MSN is superior to free DOX in terms of therapeutic efficacy and side effects due to the enhanced permeability and retention effects and lower pH in tumor areas. We believe that this developed MSN based delivery system will provide a promising nanodevice for tumor therapy.

Natural gelatin capped mesoporous silica nanoparticles for intracellular acid-triggered drug delivery

This paper proposed a natural gelatin capped mesoporous silica nanoparticles (MSN@Gelatin) based pH-responsive delivery system for intracellular anticancer drug controlled release. In this system, the gelatin, a proteinaceous biopolymer derived from the processing of animal collagen, was grafted onto the MSN to form a capping layer via temperature-induced gelation and subsequent glutaraldehyde mediated cross-linking, resulting in gelatin coated MSN. At neutral pH, the gelatin capping layer could effectively prohibit the release of loaded drug molecules. However, the slightly acidic environment would lead to enhanced electrostatic repulsion between the gelatin and MSN, giving rise to uncapping and the subsequent controlled release of the entrapped drug. As a proof-of-concept, doxorubicin (DOX) was selected as the model anticancer drug. The loading and pH-responsive release experiments demonstrated that the system had excellent loading efficiency (47.3 mmol g(-1) SiO2), and almost no DOX was leaked at neutral. After being in the slightly acidic condition, the DOX release from the DOX-loaded MSN@Gelatin (DOX/MSN@Gelatin) occurred immediately. The cellular uptake and release studies using Hep-G2 hepatoma cells indicated that the DOX/MSN@Gelatin could be endocytosed and accumulated within lysosomes. Triggered by acidic endosomal pH, the intracellular release of the loaded DOX was obviously eventuated. Further cell viability results demonstrated that DOX/MSN@Gelatin exhibited dose-dependent toxicity and high killing efficacy (IC50 = 17.27 ± 0.63 μg mL(-1)), whereas the MSN@Gelatin showed negligible cytotoxicity (IC50 > 100 μg mL(-1)). This biocompatible and effective delivery system will provide great potential for developing delivery of cancer therapeutic agents.

Photosensitizer-incorporated quadruplex DNA-gated nanovechicles for light-triggered, targeted dual drug delivery to cancer cells

A novel light-operated vehicle for targeted intracellular drug delivery is constructed using photosensitizer-incorporated G-quadruplex DNA-capped mesoporous silica nanoparticles. Upon light irradiation, the photosensitizer generates ROS, causing the DNA capping to be cleaved and allowing cargo to be released. Importantly, this platform makes it possible to develop a drug-carrier system for the synergistic combination of chemotherapy and PDT for cancer treatment with spatial/temporal control. Furthermore, the introducing of targeting ligands further improves tumor targeting efficiency. The excellent biocompatibility, cell-specific intracellular drug delivery, and cellular uptake properties set up the basis for future biomedical application that require in vivo controlled, targeted drug delivery.

Functionalized silica nanoparticles: a platform for fluorescence imaging at the cell and small animal levels

Going in vivo, including living cells and the whole body, is very important for gaining a better understanding of the mystery of life and requires specialized imaging techniques. The diversity, composition, and temporal-spatial variation of life activities from cells to the whole body require the analysis techniques to be fast-response, noninvasive, highly sensitive, and stable, in situ and in real-time. Functionalized nanoparticle-based fluorescence imaging techniques have the potential to meet such needs through real-time and noninvasive visualization of biological events in vivo. Functionalized silica nanoparticles (SiNPs) doped with fluorescent dyes appear to be an ideal and flexible platform for developing fluorescence imaging techniques used in living cells and the whole body. We can select and incorporate different dyes inside the silica matrix either noncovalently or covalently. These form the functionalized hybrid SiNPs, which support multiplex labeling and ratiometric sensing in living systems. Since the silica matrix protects dyes from outside quenching and degrading factors, this enhances the photostability and biocompatibility of the SiNP-based probes. This makes them ideal for real-time and long-time tracking. One nanoparticle can encapsulate large numbers of dye molecules, which amplifies their optical signal and temporal-spatial resolution response. Integrating fluorescent dye-doped SiNPs with targeting ligands using various surface modification techniques can greatly improve selective recognition. Along with the endocytosis, functionalized SiNPs can be efficiently internalized into cells for noninvasive localization, assessment, and monitoring. These unique characteristics of functionalized SiNPs substantially support their applications in fluorescence imaging in vivo. In this Account, we summarize our efforts to develop functionalized dye-doped SiNPs for fluorescence imaging at the cell and small animal levels. We first discuss how to design and construct various functionalized dye-doped SiNPs. Then we describe their properties and imaging applications in cell surface receptor recognition, intracellular labeling, tracking, sensing, and controlled release. Additionally, we have demonstrated the promising application of dye-doped SiNPs as contrast imaging agents for in vivo fluorescence imaging in small animals. We expect these functionalized dye-doped SiNPs to open new opportunities for biological and medical research and applications.

Poly(propylene imine) dendrimer caps on mesoporous silica nanoparticles for redox-responsive release: smaller is better

To elucidate the importance of the size of capping agents in stimulus-induced release systems from mesoporous silica nanoparticles (MSNs), the effectiveness of poly(propylene imine) dendrimers in controlling the model drug release was studied. MCM-41-type MSNs were synthesized and characterized. Fluorescent compounds (fluorescein disodium salt and carboxyfluorescein) were loaded in the porous structure of the MSNs and entrapped in the silica matrix with the dendrimers of generations I through V by anchoring dendrimers on the MSN surface through disulfide bonds. Stimulus-induced release of the cargo was studied in the presence of dithiothreitol (DTT). Dendrimers of generations I and II were found to be more effective in model drug retention and subsequent release than higher generations. Moreover, MSNs modified with larger amounts of dendrimers lowered the cargo release in the presence of DTT. These findings are of importance for optimizing drug delivery systems based on responsive MSNs as they enable tuning of the amount of the released cargo by choosing the capping agent of appropriate size.

Hindered disulfide bonds to regulate release rate of model drug from mesoporous silica

With the advancement of drug delivery systems based on mesoporous silica nanoparticles (MSNs), a simple and efficient method regulating the drug release kinetics is needed. We developed redox-responsive release systems with three levels of hindrance around the disulfide bond. A model drug (rhodamine B dye) was loaded into MSNs' mesoporous voids. The pore opening was capped with β-cyclodextrin in order to prevent leakage of drug. Indeed, in absence of a reducing agent the systems exhibited little leakage, while the addition of dithiothreitol cleaved the disulfide bonds and enabled the release of cargo. The release rate and the amount of released dye were tuned by the level of hindrance around disulfide bonds, with the increased hindrance causing a decrease in the release rate as well as in the amount of released drug. Thus, we demonstrated the ability of the present mesoporous systems to intrinsically control the release rate and the amount of the released cargo by only minor structural variations. Furthermore, an in vivo experiment on zebrafish confirmed that the present model delivery system is nonteratogenic.

Targeting cancer cells with controlled release nanocapsules based on a single aptamer

Molecular gates have received considerable attention as drug delivery systems. More recently, aptamer-based gates showed great potential in overcoming major challenges associated with drug delivery by means of nanocapsules. Based on a switchable aptamer nanovalves approach, we herein report the first demonstration of an engineered single molecular gate that directs nanoparticles to cancer cells and subsequently delivers the payload in a controllable fashion.

ATP-responsive controlled release system using aptamer-functionalized mesoporous silica nanoparticles

Adenosine-5'-triphosphate (ATP) is a multifunctional nucleotide, which plays a vital role in many biological processes, including muscle contraction, cells functioning, synthesis and degradation of important cellular compounds, and membrane transport. Thus, the development of ATP-responsive controlled release system for bioorganism application is very significative. Here, an original and facile ATP-responsive controlled release system consisting of mesoporous silica nanoparticles (MSN) functionalized with an aptamer as cap has been designed. In this system, the ATP aptamer was first hybridized with arm single-stranded DNA1 (arm ssDNA1) and arm single-stranded DNA2 (arm ssDNA2) to form the sandwich-type DNA structure and then grafted onto the MSN surface through click chemistry approach, resulting in blockage of pores and inhibition of guest molecules release. In the presence of ATP, the ATP aptamer combined with ATP and got away from the pore, leaving the arm ssDNA1 and ssDNA2 on the surface of MSN. The guest molecules can be released because single-stranded DNA is flexible. The release of the guest molecules from this system then can be triggered by the addition of ATP. As a proof-of-principle, Ru(bipy)(3)(2+) was selected as the guest molecules, and the ATP-responsive loading and release of Ru(bipy)(3)(2+) have been investigated. The results demonstrate that the system had excellent loading efficiency (215.0 μmol g(-1) SiO(2)) and the dye release percentage can reach 83.2% after treatment with 20 mM ATP for 7 h. Moreover, the ATP-responsive behavior shows high selectivity with ATP analogues. However, the leakage of Ru(bipy)(3)(2+) molecule is neglectable if ATP was not added, indicating an excellent capping efficiency. Interestingly, this system can respond not only to the commercial ATP but also to the ATP extracted from living cells. By the way, this system is also relatively stable in mouse serum solution at 37 °C. This proof of concept might promote the application of ATP-responsive devices and can also provide an idea to design various target-responsive systems using other aptamers as cap.