Real-Time In Vivo Quantitative Monitoring of Drug Release by Dual-Mode Magnetic Resonance and Upconverted Luminescence Imaging

Supramolecular Nano-Tracker for Real-Time Tracking of Drug Release and Efficient Combination Therapy

Real-time tracking of drug release from nanomedicine in vivo is crucial for optimizing its therapeutic efficacy in clinical settings, particularly in dosage control and determining the optimal therapeutic window. However, most current real-time tracking systems require a tedious synthesis and purification process. Herein, a supramolecular nano-tracker (SNT) capable of real-time tracking of drug release in vivo based on non-covalent host-guest interactions is presented. By integrating multiple cavities into a single nanoparticle, SNT achieves co-loading of drugs and probes while efficiently quenching the photophysical properties of the probe through host-guest complexation. Moreover, SNT is readily degraded under hypoxic tumor tissues, leading to the simultaneous release of drugs and probes and the fluorescence recovery of probes. With this spatial and temporal consistency in drug loading and fluorescence quenching, as well as drug release and fluorescence recovery, SNT successfully achieves real-time tracking of drug release in vivo (Pearson r = 0.9166, R2 = 0.8247). Furthermore, the released drugs can synergize effectively with fluorescent probes upon light irradiation, achieving potent chemo-photodynamic combination therapy in 4T1-bearing mice with a significantly improved survival rate (33%), providing a potential platform to significantly advance the development of nanomedicine and achieve optimal therapeutic effects in the clinic.

Designing Mesoporous Prussian Blue@zinc Phosphate Nanoparticles with Hierarchical Pores for Varisized Guest Delivery and Photothermally-Augmented Chemo-Starvation Therapy

Background

With the rapid development of nanotechnology, constructing a multifunctional nanoplatform that can deliver various therapeutic agents in different departments and respond to endogenous/exogenous stimuli for multimodal synergistic cancer therapy remains a major challenge to address the inherent limitations of chemotherapy.

Methods

Herein, we synthesized hollow mesoporous Prussian Blue@zinc phosphate nanoparticles to load glucose oxidase (GOx) and DOX (designed as HMPB-GOx@ZnP-DOX NPs) in the non-identical pore structures of their HMPB core and ZnP shell, respectively, for photothermally augmented chemo-starvation therapy.

Results

The ZnP shell coated on the HMPB core, in addition to providing space to load DOX for chemotherapy, could also serve as a gatekeeper to protect GOx from premature leakage and inactivation before reaching the tumor site because of its degradation characteristics under mild acidic conditions. Moreover, the loaded GOx can initiate starvation therapy by catalyzing glucose oxidation while causing an upgradation of acidity and H2O2 levels, which can also be used as forceful endogenous stimuli to trigger smart delivery systems for therapeutic applications. The decrease in pH can improve the pH-sensitivity of drug release, and O2 can be supplied by decomposing H2O2 through the catalase-like activity of HMPBs, which is beneficial for relieving the adverse conditions of anti-tumor activity. In addition, the inner HMPB also acts as a photothermal agent for photothermal therapy and the generated hyperthermia upon laser irradiation can serve as an external stimulus to further promote drug release and enzymatic activities of GOx, thereby enabling a synergetic photothermally enhanced chemo-starvation therapy effect. Importantly, these results indicate that HMPB-GOx@ZnP-DOX NPs can effectively inhibit tumor growth by 80.31% and exhibit no obvious systemic toxicity in mice.

Conclusion

HMPB-GOx@ZnP-DOX NPs can be employed as potential theranostic agents that incorporate multiple therapeutic modes to efficiently inhibit tumors.

Mixed-Ligand Metal-Organic Frameworks for All-in-One Theranostics with Controlled Drug Delivery and Enhanced Photodynamic Therapy

Mixed-ligand metal-organic frameworks (MOFs) multiply the properties and improve the versatility of conventional MOFs for theranostic applications. A tumor targeting and tumoral microenvironment-responsive system is significant for specific and efficient cancer theranostics. Herein, we report a kind of versatile mixed-porphyrin ligand MOF as a multifunctional matrix for multimodality-imaging-guided synergistic therapy. Tetrakis(4-carboxyphenyl)porphyrin (TCPP) shows the properties of fluorescence (FL) and photodynamic therapy (PDT), while Mn-TCPP owns magically the properties of T1-weighted magnetic resonance (MR) imaging and photothermal conversion for photothermal imaging and photothermal therapy (PTT). Because of the same coordination capacity and mode of TCPP and Mn-TCPP to Zr4+ ions, MOFs with adjustable ligand ratios were easily prepared. The mixed-ligand MOFs exhibited a high drug loading capacity for 10-hydroxycamptothecin (HCPT, 65%). After modification with hyaluronic acid (HA) through a disulfide bond (-S-S-), the MOF-S-S-HA composites possess enhanced PDT and tumor-targeted redox-responsive drug release properties due to the -S-S- bond. Thus, excellent fluorescence, MR, and photothermal trimodality imaging, redox-responsive drug release, and enhanced PDT/PTT are integrated together in the mixed-ligand MOFs as "all-in-one" theranostic agents.

Intracellular Self-Immolative Polyprodrug with Near-Infrared Light Guided Accumulation and in Vivo Visualization of Drug Release

The selective accumulation and real-time monitoring of drug release at tumor site are the key bottlenecks to the clinical translation of polyprodrug. Herein, an intracellular self-immolative polyprodrug (PMTO) is exploited, which not only shows the enhanced cellular internalization and selective accumulation in tumor site under the mild hyperthermia triggered by laser irradiation, but also possesses the self-monitoring drug release ability in vivo. The polyprodrug amphiphiles are synthesized by sequential esterification reaction, and hydrophilic poly(ethylene glycol) serves as blocking agent. On account of the mild hyperthermia produced by PMTO under the laser irradiation at tumor site, the cell membranous permeability increases, resulting in the enhanced cellular internalization and drug accumulation in tumor. After internalized by cells, the self-immolative PMTO nanoparticles can release free mitoxantrone (MTO) in intracellular reductive environment, and ratiometric photoacoustic imaging based on distinct signals between MTO and PMTO is presented to trace the drug release in vivo. Finally, this self-monitoring polyprodrug presents significant tumor suppression efficacy, which exhibits great potential for guiding the clinical medication in cancer treatment.

Engineered lanthanide-doped upconversion nanoparticles for biosensing and bioimaging application

Various fluctuations of intracellular ions, biomolecules, and other conditions in the physiological environment play crucial roles in fundamental biological processes. These factors are of great importance for analysis in biomedical detection. Nevertheless, developments of the simple, rapid, and accurate proof for specific detection still encounter major challenges. Upconversion nanoparticles (UCNPs), which could absorb multiple low-energy near-infrared light (NIR) photon excitation and emits high-energy photons caused by anti-Stokes shift, show unique upconversion luminescence (UCL) properties, for example, sharp emission band, high physicochemical stability like near-zero photobleaching, photo blinking in biological tissues, and long luminescence lifetime. Furthermore, the NIR used for the light source to excite UCNPs enable lower photo-damage effect and deeper penetration of tissue, and in the meantime, it can avoid the auto-fluorescence and light scattering from biological tissue interference. Thus, the lanthanide-doped UCNP-based functional platform with controlled structure, crystalline phase, size, and multicolor emission has become an appropriate nanomaterial for bioapplications such as biosensing, bioimaging, drug release, and therapies. In this review, the recent progress about synthesis and biomedical applications of UCNPs related to sensing and bioimaging is summarized. Firstly, the different luminescence mechanisms of the upconversion process are presented. Secondly, four of the most common methods for synthesizing UCNPs are compared as well as the advantages and disadvantages of these synthetic routes. Meanwhile, the surface modification of lanthanide-doped UCNPs was introduced to pave the way for their biochemistry applications. Next, this review detailed the biological applications of lanthanide-doped UCNPs, particularly in bioimaging, including UCL and multi-modal imaging and biosensing (monitoring intracellular ions and biomolecules). Finally, the challenges and future perspectives in materials science and biomedical fields of UCNPs are concluded: the low quantum yield of the upconversion process should be considered when they are executed as imaging contrast agents. And the biosafety of lanthanide-doped UCNPs needs to be evaluated.

Application of lanthanide-doped upconversion nanoparticles for cancer treatment: a review

With the excellent ability to transform near-infrared light to localized visible or UV light, thereby achieving deep tissue penetration, lanthanide ion-doped upconversion nanoparticles (UCNP) have emerged as one of the most striking nanoscale materials for more effective and safer cancer treatment. Up to now, UCNPs combined with photosensitive components have been widely used in the delivery of chemotherapy drugs, photodynamic therapy and photothermal therapy. Applications in these directions are reviewed in this article. We also highlight microenvironmental tumor monitoring and precise targeted therapies. Then we briefly summarize some new trends and the existing challenges for UCNPs. We hope this review can provide new ideas for future cancer treatment based on UCNPs.

Polymer-Functionalized Upconversion Nanoparticles for Light/Imaging-Guided Drug Delivery

The strong upconversion luminescence (UCL) of upconversion nanoparticles (UCNPs) endows the nanoparticles with attractive features for combined imaging and drug delivery. UCNPs convert near-infrared (NIR) light into light of shorter wavelengths such as light in the ultraviolet (UV) and visible regions, which can be used for light-guided drug delivery. Although light-responsive drug delivery systems as such have been known for many years, their application in medicine is limited, as strong UV-light can be damaging to tissue; moreover, UV light will not penetrate deeply into the skin, an issue that UCNPs can now address. However, UCNPs, as obtained after synthesis, are usually hydrophobic and require further surface functionalization to be stable in plasma. Polymers can serve as versatile surface coatings, as they can provide good colloidal stability, prevent the formation of a protein corona, provide a matrix for drugs, and be stimuli-responsive. In this Review, we provide a brief overview of the most recent progress in the synthesis of UCNPs with different shapes/sizes. We will then discuss the purpose of polymer coating for drug delivery before summarizing the strategies to coat UCNPs with various polymers. We will introduce the different polymers that have so far been used to coat UCNPs with the purpose to create a drug delivery system, focusing in detail on light-responsive polymers. To expand the application of UCNPs to allow photothermal therapy or magnetic resonance imaging (MRI) or to simply enhance the loading capacity of drugs, UCNPs were often combined with other materials to generate multifunctional nanoparticles such as carbon-based NPs and nanoMOFs. We then conclude with a discussion on drug loading and release and summarize the current knowledge on the toxicity of these polymer-coated UCNPs.

The synthesis and multicolor luminescence of lanthanide doped Vernier lutetium oxyfluorides

We report a facile hydrothermal method followed by heat treatment for synthesizing monodispersed V-LuOF nanorods through which multicolor emissions are achieved in V-LuOF:Tb³⁺,xEu³⁺.

Magnetic Nanoparticles

Magnetic nanoparticles have been used in various fields such as data storage, biomedicine, or bioimaging with their unique magnetic property. With their low toxicity, the importance of magnetic nanoparticles keeps increasing especially in biological field. In this chapter, content suitable for scientific inquirers or undergraduates to acquire basic knowledge about nanotechnology is introduced and then recent research trends in nanotechnology are covered.

Silica Mesoporous Structures: Effective Nanocarriers in Drug Delivery and Nanocatalysts

The application of silica mesoporous structures in drug delivery and the removal of pollutants and organic compounds through catalytic reactions is increasing due to their unique characteristics, including high loading capacities, tunable pores, large surface areas, sustainability, and so on. This review focuses on very well-studied class of different construction mesoporous silica nano(particles), such as MCM-41, SBA-15, and SBA-16. We discuss the essential parameters involved in the synthesis of these materials with providing a diverse set of examples. In addition, the recent advances in silica mesoporous structures for drug delivery and catalytic applications are presented to fill the existing gap in the literature with providing some promising examples on this topic for the scientists in both industry and academia active in the field. Regarding the catalytic applications, mesoporous silica particles have shown some promises to remove the organic pollutants and to synthesize final products with high yields due to the ease with which their surfaces can be modified with various ligands to create appropriate interactions with target molecules. In the drug delivery process, as nanocarriers, they have also shown very good performance thanks to the easy surface functionalization but also adjustability of their porosities to providing in-vivo and in-vitro cargo delivery at the target site with appropriate rate.

Microscale Self-Assembly of Upconversion Nanoparticles Driven by Block Copolymer

Lanthanide-based upconversion nanoparticles can convert low-energy excitation to high-energy emission. The self-assembled upconversion nanoparticles with unique structures have considerable promise in sensors and optical devices due to intriguing properties. However, the assembly of isotropic nanocrystals into anisotropic structures is a fundamental challenge caused by the difficulty in controlling interparticle interactions. Herein, we report a novel approach for the preparation of the chain-like assemblies of upconversion nanoparticles at different scales from nano-scale to micro-scale. The dimension of chain-like assembly can be fine-tuned using various incubation times. Our study observed Y-junction aggregate morphology due to the flexible nature of amphiphilic block copolymer. Furthermore, the prepared nanoparticle assemblies of upconversion nanoparticles with lengths up to several micrometers can serve as novel luminescent nanostructure and offer great opportunities in the fields of optical applications.

Smart Bimodal Imaging of Hypochlorous Acid In Vivo Using a Heterobimetallic Ruthenium(II)-Gadolinium(III) Complex Probe

A unique heterobimetallic Ru(II)-Gd(III) complex, Ru-AN-Gd, is reported to serve as an effective probe for bimodal phosphorescence-magnetic resonance (MR) imaging of hypochlorous acid (HClO) in vitro and in vivo. The probe was designed by incorporating a MR contrast agent, Gd-DOTA, into a HClO-responsive bipyridine-Ru(II) complex derivative. The specific reaction between Ru-AN-Gd and HClO triggers the cleavage of an ether bond in the probe molecule, resulting in phosphorescence turn-on and MR turn-off responses to HClO. The integration of MR and phosphorescence detection modes allows the probe to be employed for detecting HClO in a quite wide concentration range (0.6-2000 μM) and for imaging HClO at various resolutions ranging from the subcellular level to the whole body without a depth limit. Its applicability was demonstrated by phosphorescence imaging of lysosomal HClO in live cells, visualization of HClO generation in a mouse arthritis model, and bimodal phosphorescence-MR imaging of HClO in drug-induced acute liver and kidney injury of a mouse. The research achievements suggested the potential of Ru-AN-Gd for diagnosis and treatment monitoring of HClO-related disease.

Magnetic resonance imaging of high-intensity focused ultrasound-stimulated drug release from a self-reporting core@shell nanoparticle platform

We developed a theranostic approach exemplifying a concept called an "exchange method" that controls and "images" drug release from nanoparticles using magnetic resonance imaging-guided high-intensity focused ultrasound. The controllable amount of released drug and therapeutic efficacy can be self-reported by associated MRI contrast changes in solution and in cells.

Complementary autophagy inhibition and glucose metabolism with rattle-structured polydopamine@mesoporous silica nanoparticles for augmented low-temperature photothermal therapy and in vivo photoacoustic imaging

Rattle-structured nanoparticles with movable cores, porous shells and hollow interiors have shown great effectiveness in drug delivery and cancer theranostics. Targeting autophagy and glucose have provided alternative strategies for cancer intervention therapy. Herein, rattle-structured polydopamine@mesoporous silica nanoparticles were prepared for in vivo photoacoustic (PA) imaging and augmented low-temperature photothermal therapy (PTT) via complementary autophagy inhibition and glucose metabolism.

Methods: The multifunctional rattle-structured nanoparticles were designed with the nanocore of PDA and the nanoshell of hollow mesoporous silica (PDA@hm) via a four-step process. PDA@hm was then loaded with autophagy inhibitor chloroquine (CQ) and conjugated with glucose consumer glucose oxidase (GOx) (PDA@hm@CQ@GOx), forming a corona-like structure nanoparticle.

Results: The CQ and GOx were loaded into the cavity and decorated onto the surface of PDA@hm, respectively. The GOx-mediated tumor starvation strategy would directly suppress the expression of HSP70 and HSP90, resulting in an enhanced low-temperature PTT induced by PDA nanocore. In addition, autophagy inhibition by the released CQ made up for the loss of low-temperature PTT and starvation efficiencies by PTT- and starvation-activated autophagy, realizing augmented therapy efficacy. Furthermore, the PDA nanocore in the PDA@hm@CQ@GOx could be also used for PA imaging.

Conclusion: Such a “drugs” loaded rattle-structured nanoparticle could be used for augmented low-temperature PTT through complementarily regulating glucose metabolism and inhibiting autophagy and in vivo photoacoustic imaging.

Designing Stimuli-Responsive Upconversion Nanoparticles that Exploit the Tumor Microenvironment

Tailoring personalized cancer nanomedicines demands detailed understanding of the tumor microenvironment. In recent years, smart upconversion nanoparticles with the ability to exploit the unique characteristics of the tumor microenvironment for precise targeting have been designed. To activate upconversion nanoparticles, various bio-physicochemical characteristics of the tumor microenvironment, namely, acidic pH, redox reactants, and hypoxia, are exploited. Stimuli-responsive upconversion nanoparticles also utilize the excessive presence of adenosine triphosphate (ATP), riboflavin, and Zn²⁺ in tumors. An overview of the design of stimulus-responsive upconversion nanoparticles that precisely target and respond to tumors via targeting the tumor microenvironment and intracellular signals is provided. Detailed understanding of the tumor microenvironment and the personalized design of upconversion nanoparticles will result in more effective clinical translation.

Photoacoustic Imaging Quantifies Drug Release from Nanocarriers via Redox Chemistry of Dye-Labeled Cargo

We report a new approach to monitor drug release from nanocarriers via a paclitaxel-methylene blue conjugate (PTX-MB) with redox activity. This construct is in a photoacoustically silent reduced state inside poly(lactic-co-glycolic acid) (PLGA) nanoparticles (PTX-MB@PLGA NPs). During release, PTX-MB is spontaneously oxidized to produce a concentration-dependent photoacoustic signal. An in vitro drug-release study showed an initial burst release (25 %) between 0-24 h and a sustained release between 24-120 h with a cumulative release of 40.6 % and a 670-fold increase in photoacoustic signal. An in vivo murine drug release showed a photoacoustic signal enhancement of up to 649 % after 10 hours. PTX-MB@PLGA NPs showed an IC50 of 78 μg mL-1 and 44.7±4.8 % decrease of tumor burden in an orthotopic model of colon cancer via luciferase-positive CT26 cells.

Recalcitrant Issues and New Frontiers in Nano-Pharmacology

Packaging of old pharma drugs into new packaging "nanoparticles" is called nano-pharmacology and the products are called nano-based drugs. The inception of nano-pharmacology research and development (R&D) is marked by the approval of the first nano-based drug Doxil® in 1995 by the Food and Drug Administration. However, even after more than two decades, today, there are only ∼20 nano-based drugs in the market to treat cancers and brain diseases. In this article we share the perspectives of nanotechnology scientists, engineers, and clinicians on the roadblocks in nano-pharmacology R&D. Also, we share our opinion on new frontiers in the field of nano-pharmacology R&D that may allow rapid and efficient transfer of nano-pharma technologies from R&D to market.

NIR nanoprobe-facilitated cross-referencing manifestation of local disease biology for dynamic therapeutic response assessment

Pharmacological interventions for effective treatment require opportune, dynamic and accurate manifestation of pathological status. Traditional clinical techniques relying on biopsy-based histological examinations and blood tests are dramatically restricted due to their invasiveness, unsatisfactory precision, non-real-time reporting and risk of complications. Although current strategies through molecular imaging enable non-invasive and spatiotemporal mapping of pathological changes in intact organisms, environment-activatable, sensitive and quantitative sensing platforms, especially for dynamic feedback of the therapeutic response, are still urgently desired in practice. Herein, we innovatively integrate deep-tissue penetrable multispectral optoacoustic tomography (MSOT) and near-infrared (NIR) optical imaging based technology by tailoring a free radical-responsive chromophore with photon-upconverting nanocrystals. During the therapeutic process, the specific reactions between the drug-stimulated reactive oxygen species (ROS) and radical-sensitive probes result in an absorption shift, which can be captured by MSOT. Meanwhile, the radical-triggered reaction also induces multispectral upconversion luminescence (UCL) responses that exhibit the opposite trend in comparison to MSOT. Such reversed-ratiometric dual-modal imaging outcomes provide an ideal cross-referencing system that guarantees the maximum sensing specificity and sensitivity, thus enabling precise disease biology evaluation and treatment assessments in vivo.

Quantitative Drug Release Monitoring in Tumors of Living Subjects by Magnetic Particle Imaging Nanocomposite

In vivo drug release monitoring provides accurate and reliable information to guide drug dosing. Image-based strategies for in vivo monitoring are advantageous because they are non-invasive and provide visualization of the spatial distribution of drug, but those imaging modalities in use (e.g., fluorescence imaging (FI) and magnetic resonance imaging (MRI)) remain inadequate because of the low tissue penetration depth (for FI) or difficulty with quantification of release rate and signal convolution with noise sources (for MRI). Magnetic particle imaging (MPI), employing superparamagnetic nanoparticles as the contrast agent and sole signal source, enables large tissue penetration and quantifiable signal intensity. These properties make it ideal for application to in vivo drug release monitoring. In this work, we design a superparamagnetic Fe₃O₄ nanocluster@poly(lactide-co-glycolide acid) core-shell nanocomposite loaded with a chemotherapy drug (doxorubicin) which serves as a dual drug delivery system and MPI quantification tracer. The as-prepared nanocomposite can degrade under a mild acidic microenvironment (pH = 6.5), which induces a sustained release of doxorubicin and gradual decomposition of the Fe₃O₄ nanocluster, causing the MPI signal changes. We showed that nanocomposite-induced MPI signal changes display a linear correlation with the release rate of doxorubicin over time (R² = 0.99). Utilizing this phenomenon, we successfully established quantitative monitoring of the release process in cell culture. We then performed in vivo drug release monitoring in a cancer therapy setting using a murine breast cancer model by injecting the nanocomposite, monitoring the drug release, and assessing the induced tumor cell kill. This study provides an improved solution for in vivo drug release monitoring compared to other available monitoring strategies. This translational strategy using a biocompatible polymer-coated iron oxide nanocomposite will be promising in future clinical use.

The Horizon of the Emulsion Particulate Strategy: Engineering Hollow Particles for Biomedical Applications

With their hierarchical structures and the substantial surface areas, hollow particles have gained immense research interest in biomedical applications. For scalable fabrications, emulsion-based approaches have emerged as facile and versatile strategies. Here, the recent achievements in this field are unfolded via an "emulsion particulate strategy," which addresses the inherent relationship between the process control and the bioactive structures. As such, the interior architectures are manipulated by harnessing the intermediate state during the emulsion revolution (intrinsic strategy), whereas the external structures are dictated by tailoring the building blocks and solidification procedures of the Pickering emulsion (extrinsic strategy). Through integration of the intrinsic and extrinsic emulsion particulate strategy, multifunctional hollow particles demonstrate marked momentum for label-free multiplex detections, stimuli-responsive therapies, and stem cell therapies.

Dynamically Reversible Iron Oxide Nanoparticle Assemblies for Targeted Amplification of T1-Weighted Magnetic Resonance Imaging of Tumors

Smart magnetic resonance (MR) contrast agents, by which MR contrast can be selectively enhanced under acidic tumor microenvironment, are anticipated to significantly improve the diagnostic accuracy. Here, we report pH-sensitive iron oxide nanoparticle assemblies (IONAs) that are cross-linked by small-molecular aldehyde derivative ligands. The dynamic formation and cleavage of hydrazone linkages in neutral and acidic environments, respectively, allow the reversible response of the nanoassemblies to pH variations. At neutral pH, IONAs are structurally robust due to the cross-linking by the strong hydrazone bonds. In acidic tumor microenvironment, the hydrazone bonds are cleaved so that the IONAs are quickly disassembled into a large number of hydrophilic extremely small-sized iron oxide nanoparticles (ESIONs). As a result, significantly enhanced T1MR contrast is achieved, as confirmed by the measurement of r1 values at different pH conditions. Such acidity-targeting MR signal amplification by the pH-sensitive IONAs was further validated in vivo, demonstrating a novel T1 magnetic resonance imaging (MRI) strategy for highly sensitive imaging of acidic tumors.

Recent Developments in Nanosensors for Imaging Applications in Biological Systems

Sensors are key tools for monitoring the dynamic changes of biomolecules and biofunctions that encode valuable information that helps us understand underlying biological processes of fundamental importance. Because of their distinctive size-dependent physicochemical properties, materials with nanometer scales have recently emerged as promising candidates for biological sensing applications by offering unique insights into real-time changes of key physiological parameters. This review focuses on recent advances in imaging-based nanosensor developments and applications categorized by their signal transduction mechanisms, namely, fluorescence, plasmonics, MRI, and photoacoustics. We further discuss the synergy created by multimodal nanosensors in which sensor components work based on two or more signal transduction mechanisms.

Aggregation-induced emission (AIE) fluorophores as imaging tools to trace the biological fate of nano-based drug delivery systems

The vigorous development of nanotechnology has been accompanied by an equally strong interest and research efforts in nano-based drug delivery systems (NDDSs). However, only a few NDDSs have been translated into clinic thus far. One of the important hurdles is the lack of tools to comprehensively and directly trace the biological fate of NDDSs. Recently, aggregation-induced emission (AIE) fluorophores have emerged as attractive bioimaging tools due to flexible controllability, negligible toxicity and superior photostability. Herein, we recapitulate the current advances in the application of AIE fluorophores to monitor NDDSs both in vitro and in vivo. Particularly, we discuss the cellular fates of self-indicating and stimuli-responsive NDDSs with AIE fluorophores. Moreover, we highlight the in vivo application of AIE agents on the long-term tracking of therapeutics and the multi-modal monitoring of diagnostics in NDDSs. Challenges and opportunities in AIE-guided exploration of NDDSs are also discussed in detail.

Facile synthesis of Silicon quantum dot-Gadolinium: A potential fluorescent/T1-T2 multimodal imaging agent

Highly stable and multifunctional fluorescent quantum dots are particularly attractive in practical applications. Here, a new kind of ultra-small-sized silicon quantum dot-gadolinium (SiQD-Gd) was successfully fabricated by a newly-designed facile hydrothermal growth and chelating method. The obtained SiQD-Gd exhibited outstanding water dispersibility, stability and good fluorescent property with the quantum yield of 11.6%. SiQD-Gd displayed a low cytotoxicity in normal cell lines (HELF, HEK293F) and tumor cell lines (H1299, A549). Meanwhile, SiQD-Gd showed excellent magnetic resonance response with r₁ relaxation rate of 10.5 mmol L^-1·s^-1 and r₂ relaxation rate of 47.5 mmol L^-1·s^-1, which are 2.5 and 7.4 times enhanced comparing to that of the commercial MR agent Magnevist. In vivo studies showed significant contrast enhancement effect of its T₁- and T₂-weighted MR imaging. In addition, in vivo fluorescent imaging for mice and zebrafish indicated its potential applications in fluorescent tracking. Thus, the excellent multimodal imaging capacity and biocompatibility of SiQD-Gd make it a potential imaging agent for clinic applications.

Core-Satellite Nanomedicines for in Vivo Real-Time Monitoring of Enzyme-Activatable Drug Release by Fluorescence and Photoacoustic Dual-Modal Imaging

It remains an unresolved challenge to achieve spatial and temporal monitoring of drug release from nanomedicines (NMs) in vivo, which is of crucial importance in disease treatment. To tackle this issue, we constructed core-satellite ICG/DOX@Gel-CuS NMs, which consist of gelatin (Gel) nanoparticles (NPs) with payloads of near-infrared fluorochrome indocyanine green (ICG) and chemo-drug doxorubicin (DOX) and surrounding CuS NPs. The fluorescence of ICG was initially shielded by satellite CuS NPs within the intact ICG/DOX@Gel-CuS NMs and increased in proportion to the amount of DOX released from NMs in response to enzyme-activated NMs degradation. For more comprehensive understanding of the drug-release profile, a theoretical model derived from computer simulation was employed to reconstruct the enzyme-activatable drug release of the ICG/DOX@Gel-CuS NMs, which demonstrated the underlying kinetics functional relationship between the released DOX amount and recovered ICG fluorescence intensity. The kinetics of drug release in vivo was assessed by administrating ICG/DOX@Gel-CuS NMs both locally and systemically into MDA-MB-231 tumor-bearing mice. Upon accumulation of ICG/DOX@Gel-CuS NMs in the tumor, overexpressed enzymes triggered the degradation of the gelatin scaffold as well as the release of DOX and ICG, which can be visually depicted with the ICG fluorescence signal increasing only in the tumor area by fluorescence imaging. Additionally, the photoacoustic signal from CuS NPs was independent from the physical status of ICG/DOX@Gel-CuS NMs and hence was utilized for real-time NMs tracking. Thus, by taking advantage of the core-satellite architecture and NMs degradability in tumor site, the DOX release profile of ICG/DOX@Gel-CuS NMs was monitored by fluorescence and photoacoustic dual-modal imaging in a real-time noninvasive manner.

Advances in the application of upconversion nanoparticles for detecting and treating cancers

The detection and treatment of cancer cells at an early stage are crucial for prolonging the survival time and improving the quality of life of patients. Upconversion nanoparticles (UCNPs) have unique physical and chemical advantages and likely provide a platform for detecting and treating cancer cells at an early stage. In this paper, the principle of UCNPs as chemical sensors based on fluorescence resonance energy transfer (FRET) has been briefly introduced. Research progress in such chemical sensors for detecting and analyzing bioactive substances and heavy metal ions at the subcellular level has been summarized. The principle of UCNP-based nanoprobe-targeting of cancer cells has been described. The research progress in using nanocomposites for cancer cell detection, namely cancer cell targeted imaging and tissue staining, has been discussed. In the field of cancer treatment, the principles and research progress of UCNPs in photodynamic therapy and photothermal therapy of cancer cells are systematically discussed. Finally, the prospects for UCNPs and remaining challenges to UCNP application in the field of cancer diagnosis and treatment are briefly described. This review provides powerful theoretical guidance and useful practical information for the research and application of UCNPs in the field of cancer.

Synthesis and Biomedical Applications of Multifunctional Nanoparticles

The accumulated knowledge of nanoparticle (NP) synthesis for the last 30 years has enabled the development of functional NPs for biomedical applications. Especially, NPs with multifunctional capabilities are gaining popularity as the demand for versatile and efficient NP agents increases. Various combinations of functional materials are integrated to form multicomponent NPs with designed size, structure, and multifunctionality. Their use as diagnostic and/or therapeutic tools is demonstrated, suggesting their application potentials in healthcare and medical practice. Here, the recent achievements in the synthesis and biomedical applications of multifunctional NPs are summarized. Starting with a brief overview regarding the advances in NP synthesis and accompanying progress in nanobiotechnology, various components to construct the multifunctional NP agents, which include polymers and mesoporous, magnetic, catalytic, and semiconducting NPs, are discussed together with their overall integration forms, such as NP assembly, hollow/porous structures, or hybrid/doped systems. Following the explanation of the features that multifunctional NP agents can offer, an outlook and a brief comment regarding the future research directions are provided.

Combination Glioma Therapy Mediated by a Dual-Targeted Delivery System Constructed Using OMCN-PEG-Pep22/DOX

Accumulating studies have investigated the efficacy of receptor-mediated delivery of hydrophobic drugs in glioma chemotherapy. Here, a delivery vehicle comprising polyethylene glycol (PEG) and oxidized nanocrystalline mesoporous carbon particles (OMCN) linked to the Pep22 polypeptide targeting the low-density lipoprotein receptor (LDLR) is designed to generate a novel drug-loaded system, designated as OMCN-PEG-Pep22/DOX (OPPD). This system effectively targets glioma cells and the blood-brain barrier and exerts therapeutic efficacy through both near-infrared (NIR) photothermal and chemotherapeutic effects of loaded doxycycline (DOX). Pathological tissue microarrays show an association of LDLR overexpression in human glioma tissue with patient survival.NIR irradiation treatment and magnetic resonance imaging results show that OPPD reaches the effective glioma-killing temperature in a glioma-bearing rat with a skull bone removal model and considerably reduces glioma sizes relative to the drug-loaded system without the Pep22 peptide modification and the control respectively. Thus, OPPD not only effectively targets LDLR-overexpressing glioma but also exerts a dual therapeutic effect by transporting DOX into the glioma and generating thermal effects with near-infrared irradiation to kill tumor cells. These collective findings support the utility of the novel OPPD drug-loaded system as a promising drug delivery vehicle for clinical application in glioma therapy.

Metal-Organic Framework-Based Nanoplatform for Intracellular Environment-Responsive Endo/Lysosomal Escape and Enhanced Cancer Therapy

Nowadays, efficient endo/lysosomal escape and the subsequent release of drugs into the cytosol are the major obstacles for nanoplatform-based cancer therapy. Herein, we first report a metal-organic framework-based nanoplatform (doxorubicin@ZIF-8@AS1411) for intracellular environment-responsive endo/lysosomal escape and enhanced cancer therapy. In our system, the nanoplatform was first targeted toward the cancer cells. Then, it was entrapped in endo/lysosomes, where pH-responsive decomposition occurred and abundant Zn ions were released. The released Zn ions could induce an influx of counterions, promote reactive singlet oxygen (ROS) generation to rupture the endo/lysosomal membrane, and accelerate the release of anticancer drugs in the cytosol. Finally, the released drugs and the generation of ROS could synergistically enhance cancer therapy. With excellent biocompatibility, effective endo/lysosomal escape, and enhanced therapeutic effect, the novel drug delivery systems are supposed to become a promising anticancer agent for cancer therapy and bring more opportunities for biomedical application.

Controlled drug release with surface-capped mesoporous silica nanoparticles and its label-free in situ Raman monitoring

Mesoporous silica nanoparticles (MSNs) have drawn attention as efficient nanocarriers for drug delivery systems owing to their unique physiochemical properties. However, systemically controlling the kinetics of drug release from the nanocarriers and in situ monitoring of the drug release are still challenging. Here, we report surface-capped MSNs used for controlled drug release and demonstrate label-free in situ Raman monitoring of released drugs based on the molecule-specific spectral fingerprints. By capping the surface of MSNs with amine moieties, gold nanoparticles, and albumin, we achieved high loading efficiencies (up to 97%) of doxorubicin and precisely controlled drug release stimulated by changing pH value. Moreover, we monitored in real-time drug release profile and visualized cellular distribution of the delivered drug at nanoscale based on its intrinsic Raman peak. Finally, we evaluated drug responses in cancer cells and normal cells to investigate whether capped-dMSNs exhibit selective drug release. Our findings would be beneficial for designing smart drug carriers and directly monitoring the release behavior of drugs in actual cellular environments.

Noninvasive real-time monitoring of local drug release using nano-Au-absorbed self-decomposable SiO2 carriers

Real time monitoring of drug release at specific local sites by a non-invasive imaging method is critical in patient-specific drug administration in order to avoid insufficient or excess drug dosing. In the present work, we designed a specific carrier system for such a purpose using self-decomposable SiO2 nanoparticles (NPs) with the drug being loaded in the center and Au NPs on the SiO2 NPs as the imaging agent. We discovered a correlation between the drug release from the carrier and the morphological evolution of Au NPs, which also left the carrier and changed their aggregation states along with the drug release process. This finding enabled the real time monitoring of the drug release at local sites (e.g. tumor) in a quantitative manner by recording the CT signal evolution of the Au NPs, as demonstrated in vivo using mice bearing Colo-205 xenografts. The present work provided a promising platform for non-invasive real time tracking on the localized drug release, enabling a variety of personalized therapeutic applications.

Multifunctional nanomedicine with silica: Role of silica in nanoparticles for theranostic, imaging, and drug monitoring

The idea of multifunctional nanomedicine that enters the human body to diagnose and treat disease without major surgery is a long-standing dream of nanomaterials scientists. Nanomaterials show incredible properties that are not found in bulk materials, but achieving multi-functionality on a single material remains challenging. Integrating several types of materials at the nano-scale is critical to the success of multifunctional nanomedicine device. Here, we describe the advantages of silica nanoparticles as a tool for multifunctional nano-devices. Silica nanoparticles have been intensively studied in drug delivery due to their biocompatibility, degradability, tunable morphology, and ease of modification. Moreover, silica nanoparticles can be integrated with other materials to obtain more features and achieve theranostic capabilities and multimodality for imaging applications. In this review, we will first compare the properties of silica nanoparticles with other well-known nanomaterials for bio-applications and describe typical routes to synthesize and integrate silica nanoparticles. We will then highlight theranostic and multimodal imaging application that use silica-based nanoparticles with a particular interest in real-time monitoring of therapeutic molecules. Finally, we will present the challenges and perspective on future work with silica-based nanoparticles in medicine.

Near-infrared light-activated red-emitting upconverting nanoplatform for T1-weighted magnetic resonance imaging and photodynamic therapy

Photodynamic therapy (PDT) has increasingly become an efficient and attractive cancer treatment modality based on reactive oxygen species (ROS) that can induce tumor death after irradiation with ultraviolet or visible light. Herein, to overcome the limited tissue penetration in traditional PDT, a novel near-infrared (NIR) light-activated NaScF₄: 40% Yb, 2% Er@CaF₂ upconversion nanoparticle (rUCNP) is successfully designed and synthesized. Chlorin e6, a photosensitizer and a chelating agent for Mn²⁺, is loaded into human serum albumin (HSA) that further conjugates onto rUCNPs. To increase the ability to target glioma tumor, an acyclic Arg-Gly-Asp peptide (cRGDyK) is linked to rUCNPs@HSA(Ce6-Mn). This nanoplatform enables efficient adsorption and conversion of NIR light (980 nm) into bright red emission (660 nm), which can trigger the photosensitizer Ce6-Mn complex for PDT and T₁-weighted magnetic resonance imaging (T₁-weighted MRI) for glioma diagnosis. Our in vitro and in vivo experiments demonstrate that NIR light-activated and glioma tumor-targeted PDT can generate large amounts of intracellular ROS that induce U87 cell apoptosis and suppress glioma tumor growth owing to the deep tissue penetration of irradiated light and excellent tumor-targeting ability. Thus, this nanoplatform holds potential for applications in T₁-weighted MRI diagnosis and PDT of glioma for antitumor therapy.

STATEMENT OF SIGNIFICANCE

A near-infrared (NIR) light-activated nanoplatform for photodynamic therapy (PDT) was designed and synthesized. The Red-to-Green (R/G) ratio of NaScF₄: 40% Yb, 2% Er almost reached 9, a value that was much higher than that of a traditional Yb/Er-codoped upconversion nanoparticle (rUCNP). By depositing a CaF₂ shell, the red-emission intensities of the rUCNPs were seven times strong as that of NaScF₄: 40% Yb, 2% Er. The enhanced red-emitting rUCNPs could be applied in many fields such as bioimaging, controlled release, and real-time diagnosis. The nanoplatform had a strong active glioma-targeting ability, and all results achieved on subcutaneous glioma demonstrated that our NIR light-activated red-emitting upconverting nanoplatform was efficient for PDT. By loading Ce6-Mn complex into rUCNPs@HSA-RGD, the nanoplatform could be used as a T₁-weighted magnetic resonance imaging agent for tumor diagnosis.

Photophysical characterization of a highly luminescent divalent-europium-containing azacryptate

We report a new luminescent EuII-containing complex. The complex is excited with visible light, leading to emission centered at 447 nm with a lifetime of 1.25 μs. Computational studies suggest that the steric bulk of the ligand is a major factor influencing the wavelength of emission.

MSN-on-a-Chip: Cell-Based Screenings Made Possible on a Small-Molecule Microarray of Native Natural Products

Standard small-molecule microarrays (SMMs) are not well-suited for cell-based screening assays. Of the few attempts made thus far to render SMMs cell-compatible, all encountered major limitations. Here we report the first mesoporous silica nanoparticle (MSN)-on-a-chip platform capable of allowing high-throughput cell-based screening to be conducted on SMMs. By making use of a glass surface on which hundreds of MSNs, each encapsulated with a different native natural product, were immobilized in spatially defined manner, followed by on-chip mammalian cell growth and on-demand compound release, high-content screening was successfully carried out with readily available phenotypic detection methods. By combining this new MSN-on-a-chip system with small interfering RNA technology for the first time, we discovered that (+)-usniacin possesses synergistic inhibitory properties similar to those of olaparib (an FDA-approved drug) in BRCA1-knockdown cancer cells.

Precise targeting of cancer metastasis using multi-ligand nanoparticles incorporating four different ligands

Metastasis displays a highly heterogeneous cellular population with cancer cells continuously evolving. As a result, a single-ligand nanoparticle cannot account for the continuously changing expression of targetable biomarkers over time and space. To effectively direct nanoparticles to metastasis, we developed a multi-ligand nanoparticle by using four different types of ligands on the same nanoparticle that target biomarkers on the endothelium associated with metastatic disease. These vascular targets included αvβ3 integrin, P-selectin, EGFR and fibronectin. Using terminal and in vivo imaging studies, the targeting performance of the multi-ligand nanoparticles was compared to the single-ligand nanoparticle variants. All four single-ligand nanoparticle variants achieved significant targeting of lung metastasis in the 4T1 mouse model of breast cancer metastasis with about 2.5% of the injected dose being deposited into metastasis. A dual-ligand nanoparticle resulted in a nearly 2-fold higher deposition into lung metastases than its single-ligand counterparts. The multi-ligand nanoparticle significantly outperformed its targeting nanoparticle counterparts achieving a deposition of ∼7% of its injected nanoparticles into lung metastases. Using the high sensitivity of radionuclide imaging, PET imaging showed that a multi-ligand nanoparticle labeled with [18F]fluoride was able to precisely target metastatic disease at its very early stage of development in three different animal models of metastatic breast cancer.

Surface impact on nanoparticle-based magnetic resonance imaging contrast agents

Magnetic resonance imaging (MRI) is one of the most widely used diagnostic tools in the clinic. To improve imaging quality, MRI contrast agents, which can modulate local T1 and T2 relaxation times, are often injected prior to or during MRI scans. However, clinically used contrast agents, including Gd3+-based chelates and iron oxide nanoparticles (IONPs), afford mediocre contrast abilities. To address this issue, there has been extensive research on developing alternative MRI contrast agents with superior r1 and r2 relaxivities. These efforts are facilitated by the fast progress in nanotechnology, which allows for preparation of magnetic nanoparticles (NPs) with varied size, shape, crystallinity, and composition. Studies suggest that surface coatings can also largely affect T1 and T2 relaxations and can be tailored in favor of a high r1 or r2. However, the surface impact of NPs has been less emphasized. Herein, we review recent progress on developing NP-based T1 and T2 contrast agents, with a focus on the surface impact.

pH-responsive theranostic nanocomposites as synergistically enhancing positive and negative magnetic resonance imaging contrast agents

BACKGROUND

The rational design of theranostic nanoprobe to present responsive effect of therapeutic potency and enhanced diagnostic imaging in tumor milieu plays a vital role for efficient personalized cancer therapy and other biomedical applications. We aimed to afford a potential strategy to pose both T1- and T2-weighted MRI functions, and thereby realizing imaging guided drug delivery and targeted therapy.

RESULTS

Theranostic nanocomposites Mn-porphyrin&Fe3O4@SiO2@PAA-cRGD were fabricated and characterized, and the nanocomposites were effectively used in T1- and T2-weighted MRI and pH-responsive drug release. Fluorescent imaging also showed that the nanocomposites specifically accumulated in lung cancer cells by a receptor-mediated process, and were nontoxic to normal cells. The r2/r1 ratio was 20.6 in neutral pH 7.4, which decreased to 7.7 in acidic pH 5.0, suggesting the NCs could act as an ideal T1/T2 dual-mode contrast agent at acidic environments of tumor. For in vivo MRI, T1 and T2 relaxation was significantly accelerated to 55 and 37%, respectively, in the tumor after i.v. injection of nanocomposites.

CONCLUSION

The synthesized nanocomposites exhibited highly sensitive MRI contrast function no matter in solution, cells or in vivo by synergistically enhancing positive and negative magnetic resonance imaging signals. The nanocomposites showed great potential for integrating imaging diagnosis and drug controlled release into one composition and providing real-time imaging with greatly enhanced diagnostic accuracy during targeted therapy.