Aptamer-Functionalized Upconverting Nanoformulations for Light-Switching Cancer-Specific Recognition and In Situ Photodynamic-Chemo Sequential Theranostics

Aptamer-controlled stimuli-responsive drug release

Aptamers have been widely researched and applied in nanomedicine due to their programmable, activatable, and switchable properties. However, there are few reviews on aptamer-controlled stimuli-responsive drug delivery. This article highlights the mechanisms and advantages of aptamers in the construction of stimuli-responsive drug delivery systems. We summarize the assembly/reconfiguration mechanisms of aptamers in controlled release systems. The assembly and drug release strategies of drug delivery systems are illustrated. Specifically, we focus on the binding mechanisms to the target and the factors that induce/inhibit the binding to the stimuli, such as strand, pH, light, and temperature. The applications of aptamer-based stimuli-responsive drug release are elaborated. The challenges are discussed, and the future directions are proposed.

Therapeutic targeting of the protein tyrosine kinase-7 in cancer: an overview

The protein tyrosine kinase-7 (PTK7) is an evolutionarily conserved transmembrane receptor that has emerged as a potential therapeutic target for human tumors. PTK7 is a pseudokinase that is involved in the modulation of the Wnt signaling pathway through interactions with other receptors. These interactions result in targeted gene activation that regulates cell polarity, migration, and proliferation during embryogenesis. Aside of this role during development, PTK7 has been shown as overexpressed in numerous cancers including colon carcinoma, leukemia, neuroblastoma, hepatoma, and ovarian cancer. The activity of PTK7 and the direct correlation with poor prognosis have fostered preclinical investigations and phase I clinical trials, aiming at inhibiting PTK7 and inducing antitumoral effects. In this review, we provide an exhaustive overview of the diverse approaches that use PTK7 as a new molecular target for cancer therapy in different tumor types. We discuss current therapies and future strategies including chimeric antigen receptor-T cells, antibody-drug conjugates, aptamers, based on up-to-date literature and ongoing research progress.

Aptamer-mediated therapeutic strategies provide a potential approach for cancer

The treatment of tumors still faces considerable challenges. While conventional treatments such as surgery, chemotherapy, and radiation therapy provide some curative effects, their side effects and limitations highlight the importance of finding more precise treatment strategies. Aptamers have become an important target molecule in the field of drug delivery systems due to their good affinity and targeting, and they have gradually become an important link from basic research to clinical application. In this paper, we discussed the latest progress of aptamer-mediated nanodrugs, as well as aptamer-mediated photodynamic therapy, photothermal therapy, and immunotherapy strategies for tumor treatment, and explored the possibility of aptamer-mediated therapy for accurate tumor treatment. The purpose of this review is to provide novel insights for treating tumors with aptamer-mediated therapies by summarizing these innovative strategies, thereby ultimately enhancing the therapeutic efficacy for cancer patients.

Upconversion Nanoparticles Based Sensing: From Design to Point-of-Care Testing

Rare earth-doped upconversion nanoparticles (UCNPs) have achieved a wide range of applications in the sensing field due to their unique anti-Stokes luminescence property, minimized background interference, excellent biocompatibility, and stable physicochemical properties. However, UCNPs-based sensing platforms still face several challenges, including inherent limitations from UCNPs such as low quantum yields and narrow absorption cross-sections, as well as constraints related to energy transfer efficiencies in sensing systems. Therefore, the construction of high-performance UCNPs-based sensing platforms is an important cornerstone for conducting relevant research. This work begins by providing a brief overview of the upconversion luminescence mechanism in UCNPs. Subsequently, it offers a comprehensive summary of the sensors' types, design principles, and optimized design strategies for UCNPs sensing platforms. More cost-effective and promising point-of-care testing applications implemented based on UCNPs sensing systems are also summarized. Finally, this work addresses the future challenges and prospects for UCNPs-based sensing platforms.

Multiple miRNA Detection through a Suspended Microbead Array Encoded by Triple-Color Upconversion Luminescent Nanotags via Bi-Beam Splitter Hybrid-Multitrap Optical Tweezers

In recent years, optical tweezers have become a novel tool for biodetection, and to improve the inefficiency of a single trap, the development of multitraps is required. Herein, we constructed a set of hybrid multitrap optical tweezers with the balance of stability and flexibility by the combination of two different beam splitters, a diffraction optical element (DOE) and galvano mirrors (GMs), to capture polystyrene (PS) microbeads in aqueous solutions to create an 18-trap suspended array. A sandwich hybridization strategy of DNA-miRNA-DNA was adopted to detect three kinds of target miRNAs associated with triple negative breast cancer (TNBC), in which different upconversion nanoparticles (UCNPs) with red, green, and blue emissions were applied as luminescent tags to encode the carrier PS microbeads to further indicate the levels of the targets. With encoded luminescent microbeads imaged by a three-channel microscopic system, the biodetection displayed high sensitivity with low limits of detection (LODs) of 0.27, 0.32, and 0.33 fM and exceptional linear ranges of 0.5 fM to 1 nM, 0.7 fM to 1 nM, and 1 fM to 1 nM for miR-343-3p, miR-155, and miR-199a-5p, respectively. In addition, this bead-based assay method was demonstrated to have the potential for being applied in patients' serum by satisfactory standard addition recovery experiment results.

The construction of CRISPR/Cas9-mediated FRET 16S rDNA sensor for detection of Mycobacterium tuberculosis

The simple and efficient detection of nucleic acids is important in the diagnosis of tuberculosis (TB) caused by Mycobacterium tuberculosis (M. tuberculosis). However, base mismatch will lead to false positive and false negative nucleic acid test, which seriously interferes with the accuracy of the final results. Herein, we demonstrated a CRISPR/Cas-9-mediated fluorescent strategy utilizing fluorescence resonance energy transfer (FRET) for the detection of bacteria. High-variable region of M. tuberculosis 16S rDNA fragment was used as the target, and CRISPR/Cas9 was used as the recognition element. The binding of the P1 probe of upconversion nanoparticles (UCNPs) @SiO₂-P1 and the P2 probe of Fe₃O₄@Au-P2 caused the fluorescence quenching of UCNPs. In the presence of the target, the P2 probe hybridized with the target to form double-stranded DNA (dsDNA), which was recognized and cleaved by CRISPR/Cas9, resulting in the breaking of the P1-P2 duplex linkage. UCNPs moved away from Fe₃O₄@Au under a magnetic field, and the fluorescence signal was restored; bacteria were detected under the excitation of a 980 nm laser source. Using the CRISPR/Cas-9-mediated system, the sensor could distinguish single-base mismatches in 10 bases from the protospacer adjacent motif (PAM) region. The limit of detection (LOD) was 20 CFU mL^-1 and the detection time was 2 h. It developed a new way of accurate nucleic acid detection for disease diagnosis.

Development of "smart" drug delivery systems for chemo/PDT synergistic treatment

Although chemotherapy and photodynamic therapy (PDT) have been developed for fighting cancer, the complex and heterogeneous nature of tumors makes it difficult for a single therapy to completely inhibit tumor growth. In order to reduce multidrug resistance of cancer cells to chemotherapeutic drugs and overcome low PDT efficiency in the hypoxic tumor microenvironment (TME), chemo/PDT synergistic treatment has received much attention in recent years. Depending on the characteristic signals of TME, various drug delivery systems can be constructed to target tumors and improve the therapeutic efficacy and the pharmacokinetic profile of anticancer drugs. This review highlights the synergistic strategies, treatment protocols, and design of chemo/PDT co-therapy in recent years to explore its scope and limitations. Taking advantage of stimuli-responsive materials and active cancer-targeting agents, cancer-targeting synergistic therapy is presented and discussed, providing ideas and suggestions for the construction of chemo/PDT co-therapy "smart" nanocarriers.

Ratiometric upconversion luminescence nanoprobes from construction to sensing, imaging, and phototherapeutics

In terms of the combined advantages of upconversion luminescence (UCL) properties and dual-signal ratiometric outputs toward specific targets, the ratiometric UCL nanoprobes exhibit significant applications. This review summarizes and discusses the recent advances in ratiometric UCL nanoprobes, mainly including the construction of nanoprobe systems for sensing, imaging, and phototherapeutics. First, the construction strategies are introduced, involving different types of nanoprobe systems, construction methods, and ratiometric dual-signal modes. Then, the sensing applications are summarized, involving types of targets, sensing mechanisms, sensing targets, and naked-eye visual detection of UCL colors. Afterward, the phototherapeutic applications are discussed, including bio-toxicity, bio-distribution, biosensing, and bioimaging at the level of living cells and small animals, and biomedicine therapy. Particularly, each section is commented on by discussing the state-of-the-art relevant studies on ratiometric UCL nanoprobe systems. Moreover, the current status, challenges, and perspectives in the forthcoming studies are discussed. This review facilitates the exploration of functionally luminescent nanoprobes for excellent sensing, imaging, biomedicine, and multiple applications in significant fields.

Switching the NIR upconversion of nanoparticles for the orthogonal activation of photoacoustic imaging and phototherapy

Phototheranostics based on upconversion nanoparticles (UCNPs) offer the integration of imaging diagnostics and phototherapeutics. However, the programmable control of the photoactivation of imaging and therapy with minimum side effects is challenging due to the lack of ideal switchable UCNPs agents. Here we demonstrate a facile strategy to switch the near infrared emission at 800 nm from rationally designed UCNPs by modulating the irradiation laser into pulse output. We further synthesize a theranostic nanoagent by combining with a photosensitizer and a photoabsorbing agent assembled on the UCNPs. The orthogonal activation of in vivo photoacoustic imaging and photodynamic therapy can be achieved by altering the excitation modes from pulse to continuous-wave output upon a single 980 nm laser. No obvious harmful effects during photoexcitation was identified, suggesting their use for long-term imaging-guidance and phototherapy. This work provides an approach to the orthogonal activation of imaging diagnostics and photodynamic therapeutics.

Luminescent Lifetime Regulation of Lanthanide-Doped Nanoparticles for Biosensing

Lanthanide-doped nanoparticles possess numerous advantages including tunable luminescence emission, narrow peak width and excellent optical and thermal stability, especially concerning the long lifetime from microseconds to milliseconds. Differing from other shorter-lifetime fluorescent nanomaterials, the long lifetime of lanthanide-doped nanomaterials is independent with background fluorescence interference and biological tissue depth. This review presents the recent advances in approaches to regulating the lifetime and applications of bioimaging and biodetection. We begin with the introduction of the strategies for regulating the lifetime by modulating the core-shell structure, adjusting the concentration of sensitizer and emitter, changing energy transfer channel, establishing a fluorescence resonance energy transfer pathway and changing temperature. We then summarize the applications of these nanoparticles in biosensing, including ion and molecule detecting, DNA and protease detection, cell labeling, organ imaging and thermal and pH sensing. Finally, the prospects and challenges of the lanthanide lifetime regulation for fundamental research and practical applications are also discussed.

Smart-Polypeptide-Coated Mesoporous Fe3O4 Nanoparticles: Non-Interventional Target-Embolization/Thermal Ablation and Multimodal Imaging Combination Theranostics for Solid Tumors

Tumor theranostics hold great potential for personalized medicine in the future, and transcatheter arterial embolization (TAE) is an important clinical treatment for unresectable or hypervascular tumors. In order to break the limitation, simplify the procedure of TAE, and achieve ideal combinatorial theranostic capability, here, a kind of triblock-polypeptide-coated perfluoropentane-loaded mesoporous Fe₃O₄ nanocomposites (PFP-m-Fe₃O₄@PGTTCs) were prepared for non-interventional target-embolization, magnetic hyperthermia, and multimodal imaging combination theranostics of solid tumors. The results of systematic animal experiments by H22-tumor-bearing mice and VX2-tumor-bearing rabbits in vivo indicated that PFP-m-Fe₃O₄@PGTTC-6.3 has specific tumor accumulation and embolization effects. The tumors' growth has been inhibited and the tumors disappeared 4 weeks and ≤15 days post-injection with embolization and magnetic hyperthermia combination therapy, respectively. The results also showed an excellent effect of magnetic resonance/ultrasound/SPECT multimodal imaging. This pH-responsive non-interventional embolization combinatorial theranostics system provides a novel embolization and multifunctional theranostic candidate for solid tumors.

Engineering a Facile Aptamer "Molecule-Doctor" with Hairpin-Contained I-Motif Enables Accurate Imaging and Killing of Cancer Cells

Herein, we subtly engineered a pH and membrane receptor dual-activatable aptamer therapeutic for bispecific tumor cell imaging and in situ drug release by utilizing a hairpin-contained i-motif as the acid-responsive element to be complementary with a tumor-targeted aptamer, named as an aptamer "molecule-doctor" (pH-Apt-MD). Specifically, the pH-Apt-MD consisted of two DNA strands, where the Apt-sgc8c was labeled with AF488 and Cy3 at its 5'- and 3'-end, respectively. The I-strand, a hairpin-contained i-motif, was complementary to the Apt-sgc8c strand partially, labeled with a BHQ2 in the middle, thus generating Cy3 with quenched fluorescence and only AF488-emitted fluorescence. The double-helix region of pH-Apt-MD was designed rich in GC bases, providing sites for doxorubicin (Dox) intercalation. Once target cells were encountered, the pH-Apt-MD disassembled due to the specific recognition of the aptamer and conformation change of the i-motif, with activated fluorescence resonance energy transfer (FRET) signals between AF488 and Cy3, accompanied by Dox release in situ. Benefiting from the design of the hairpin-contained i-motif, the pH-Apt-MD presented a narrow pH response range (pH 6.0-6.8) with a transition midpoint (pH^T) of 6.50 ± 0.04. Furthermore, living cell studies revealed that the stimuli-responsive FRET signal activation of pH-Apt-MD was successfully achieved on the HCT116 cell surface with ultralow background and enhanced imaging contrast. Then, the cytotoxicity experiments proved that accurate drug release and cell killing were realized to target cells in an acidic microenvironment. As a facile double stimuli-responsive strategy, the pH-Apt-MD may hold great promise for application in precise diagnosis and therapy of cancer cells.

Detection of Amyloid β Oligomers by a Fluorescence Ratio Strategy Based on Optically Trapped Highly Doped Upconversion Nanoparticles-SiO2@Metal-Organic Framework Microspheres

Alzheimer's disease (AD), known as a progressive neurodegenerative disorder, has had a terrible impact on the health of aged people. Due to its severity, early diagnosis of AD is significant to retard the progress and provide timely treatment. Here, we report a fluorescence ratio detection of AD biomarker amyloid β oligomers (AβOs) by combining highly doped upconversion nanoparticles-SiO₂@metal-organic framework/black hole quencher (H-USM/BHQ-1) microspheres with optical tweezer (OT) microscopic imaging. Optical trapping a single microsphere not only avoids the interference of fluid viscosity but also provides a high power density laser source to efficiently stimulate upconversion luminescence (UCL) of highly doped upconversion nanoparticles (H-UCNPs). Under this condition, H-UCNPs show stronger UCL and greater power-dependent properties compared to low-doped ones. Moreover, the closely packed quenching molecules BHQ-1 on a metal-organic framework (ZIF-8) exhibit excellent quenching efficiency for upconversion 525 and 540 nm emission. Also, the luminescent resonance energy transfer efficiency reaches 89.58%. When different concentrations of AβOs are present, the UCL₅₄₀ recovers due to the decomposition of ZIF-8 and the release of BHQ-1. Using 540 and 654 nm emission ratio of highly doped UCNPs as reporters, the limit of detection reaches 28.4 pM for the quantitative determination of AβOs. Besides, this strategy is able to selectively quantify the AβO concentration. Therefore, we demonstrated the combination of optical trapping and highly doped UCNPs which is applied for the detection of AβOs with high sensitivity and specificity.

Single 808 nm near-infrared-triggered multifunctional upconverting phototheranostic nanocomposite for imaging-guided high-efficiency treatment of tumors

Multifunctional phototheranostic nanocomposites are promising for early diagnosis and precision therapy of cancer. Aim to enhance their accuracy and efficiency, in this study, we develop a single-laser excited activatable phototheranostic nanocomposite (UCNPs-D-MQ): 808 nm-excited upconverting nanoparticles (UCNPs) as the matrix programmed assembly with amphipathic compound DSPE-PEG-COOH, a near-infrared absorbing polymer DPP and the pro-photosensitizer MBQB. Upon endocytosed by cancer cells and excited by the 808 nm laser, UCNPs-D-MQ could produce high-yield reactive oxygen species (ROS) as the results of singlet oxygen generation from transferring to methylene blue, GSH depletion and ROS generation from photoactivation. It was proven both in vitro and in vivo that the nanocomposites exhibits remarkable therapeutic efficacy as well as minimal photodamage to normal cells. These results reveal UCNPs-D-MQ as a robust theranostic agent for tumor phototherapy.