Intraparticle Molecular Orbital Engineering of Semiconducting Polymer Nanoparticles as Amplified Theranostics for <i>in Vivo</i> Photoacoustic Imaging and Photothermal Therapy

Optical theranostic nanoagents that seamlessly and synergistically integrate light-generated signals with photothermal or photodynamic therapy can provide opportunities for cost-effective precision medicine, while the potential for clinical translation requires them to have good biocompatibility and high imaging/therapy performance. We herein report an intraparticle molecular orbital engineering approach to simultaneously enhance photoacoustic brightness and photothermal therapy efficacy of semiconducting polymer nanoparticles (SPNs) for <i>in vivo</i> imaging and treatment of cancer. The theranostic SPNs have a binary optical component nanostructure, wherein a near-infrared absorbing semiconducting polymer and an ultrasmall carbon dot (fullerene) interact with each other to induce photoinduced electron transfer upon light irradiation. Such an intraparticle optoelectronic interaction augments heat generation and consequently enhances the photoacoustic signal and maximum photothermal temperature of SPNs by 2.6- and 1.3-fold, respectively. With the use of the amplified SPN as the theranostic nanoagent, it permits enhanced photoacoustic imaging and photothermal ablation of tumor in living mice. Our study thus not only introduces a category of purely organic optical theranostics but also highlights a molecular guideline to amplify the effectiveness of light-intensive imaging and therapeutic nanosystems

Surface-Induced Hydrogelation for Fluorescence and Naked-Eye Detections of Enzyme Activity in Blood

Fluorescence probes have been widely applied for the detection of important analytes with high sensitivity and specificity. However, they cannot be directly applied for the detection in samples with autofluorescence such as blood. Herein, we demonstrated a simple but effective method of surface-induced self-assembly/hydrogelation for fluorescence detection of an enzyme in biological fluids including blood and cell lysates. The method utilizes an attracting glass surface to induce self-assembly of an enzyme-generating fluorescent probe. After removing the upper solution, the fluorescence turn-on at the glass surface can therefore be used for the detection of enzyme activity. By judging the thickness and color depth of hydrogels at the surface of the glass plates, we could also estimate the enzyme activity by naked eyes. Our study not only expands the application of molecular self-assembly but also provides a useful method that can be applied for direct detection of enzyme activity in complex biological samples such as blood and cell lysates

Spatiotemporal Control of Supramolecular Self-Assembly and Function

The enzyme-triggered self-assembly of peptides has flourished in controlling the self-assembly kinetics and producing nanostructures that are typically inaccessible by conventional self-assembly pathways. However, the diffusion and nanoscale chemical gradient of self-assembling peptides generated by the enzyme also significantly affect the outcome of self-assembly, which has not been reported yet. In this work, we demonstrated for the first time a spatiotemporal control of enzyme-triggered peptide self-assembly. By simply adjusting the temperature, we could change both the catalytic activity of the enzyme of phosphatase and their aggregation states. The strategy kinetically controls the production rate of self-assembling peptides and spatially controls their distribution in the system, leading to the formation of nanoparticles at 37 °C and nanofibers at 4 °C. The nanofibers showed ∼10 times higher cellular uptake by 3T3 cells than the nanoparticles, thanks to their higher stability and more ordered structures. Using such spatiotemporal control, we could prepare optimized nanoprobes with low background fluorescence, rapid and high cellular uptake, and high sensitivity. We postulate that this strategy would be very useful in general for preparing self-assembled nanomaterials with controllable morphology and function

Cellular Membrane Enrichment of Self-Assembling d‑Peptides for Cell Surface Engineering

We occasionally found that several self-assembling peptides containing d-amino acids would be preferentially enriched in cellular membranes at self-assembled stages while distributed evenly in the cytoplasma of cells at unassembled stages. Self-assembling peptides containing only l-amino acids distributed evenly in cytoplasma of cells at both self-assembled and unassembled stages. The self-assembling peptides containing d-amino acids could therefore be applied for engineering cell surface with peptides. More importantly, by integrating a protein binding peptide (a PDZ domain binding hexapeptide of WRESAI) with the self-assembling peptide containing d-amino acids, protein could also be introduced to the cell surface. This study not only provided a novel approach to engineer cell surface, but also highlighted the unusual properties and potential applications of self-assembling peptides containing d-amino acids in regenerative medicine, drug delivery, and tissue engineering

Bioinspired Coordination Micelles Integrating High Stability, Triggered Cargo Release, and Magnetic Resonance Imaging

Catechol-Fe³⁺ coordinated micelles show the potential for achieving on-demand drug delivery and magnetic resonance imaging in a single nanoplatform. Herein, we developed bioinspired coordination-cross-linked amphiphilic polymeric micelles loaded with a model anticancer agent, doxorubicin (Dox). The nanoscale micelles could tolerate substantial dilution to a condition below the critical micelle concentration (9.4 ± 0.3 μg/mL) without sacrificing the nanocarrier integrity due to the catechol-Fe³⁺ coordinated core cross-linking. Under acidic conditions (pH 5.0), the release rate of Dox was significantly faster compared to that at pH 7.4 as a consequence of coordination collapse and particle de-cross-linking. The cell viability study in 4T1 cells showed no toxicity regarding placebo cross-linked micelles. The micelles with improved stability showed a dramatically increased Dox accumulation in tumors and hence the enhanced suppression of tumor growth in a 4T1 tumor-bearing mouse model. The presence of Fe³⁺ endowed the micelles <i>T</i>₁-weighted MRI capability both in vitro and in vivo without the incorporation of traditional toxic paramagnetic contrast agents. The current work presented a simple “three birds with one stone” approach to engineer the robust theranostic nanomedicine platform

Alleviating the Liver Toxicity of Chemotherapy via pH-Responsive Hepatoprotective Prodrug Micelles

Nanocarriers have been extensively utilized to enhance the anti-tumor performance of chemotherapy, but it is very challenging to eliminate the associated hepatotoxicity. This was due to the significant liver accumulation of cytotoxic drug-loaded nanocarriers as a consequence of systemic biodistribution. To address this, we report a novel type of nanocarrier that was made of hepatoprotective compound (oleanolic acid/OA) with a model drug (methotrexate/MTX) being physically encapsulated. OA was covalently connected with methoxy poly­(ethylene glycol) (mPEG) via a hydrazone linker, generating amphiphilic mPEG–OA prodrug conjugate that could self-assemble into pH-responsive micelles (ca. 100 nm), wherein the MTX loading was ca. 5.1% (w/w). The micelles were stable at pH 7.4 with a critical micelle concentration of 10.5 μM. At the acidic endosome/lysosome microenvironment, the breakdown of hydrazone induced the micelle collapse and fast release of payloads (OA and MTX). OA also showed adjunctive anti-tumor effect with a low potency, which was proved in 4T1 cells. In the mouse 4T1 breasttumor model, MTX-loaded mPEG–OA micelles demonstrated superior capability regarding in vivo tumorgrowth inhibition because of the passive tumor targeting of nanocarriers. Unsurprisingly, MTX induced significant liver toxicity, which was evidenced by the increased liver mass and increased levels of alanine transaminase, aspartate transaminase, and lactate dehydrogenase in serum as well as in liver homogenate. MTX-induced hepatotoxicity was also accompanied with augmented oxidative stress, for example, the increase of the malondialdehyde level and the reduction of glutathione peroxidase and superoxide dismutase concentration in the liver. As expected, mPEG–OA micelles significantly reduced the liver toxicity induced by MTX because of the hepatoprotective action of OA, which was supported by the reversal of all the above biomarkers and qualitative histological analysis of liver tissue. This work offers an efficient approach for reducing the liver toxicity associated with chemotherapy, which can be applied to various antitumor drugs and hepatoprotective materials

Biomarker Displacement Activation: A General Host–Guest Strategy for Targeted Phototheranostics in Vivo

Activatable phototheranostics is highly appealing to meet the demand of precision medicine. However, although it displays efficacy in the construction of activatable photosensitizers (PSs), direct covalent decoration still shows some inevitable issues, such as complex molecular design, tedious synthesis, possible photoactivity changes, and potential toxicity. Herein, we propose a novel concept of biomarker displacement activation (BDA) using host–guest strategy. To exemplify BDA, we engineered a PS-loaded nanocarrier by utilizing a macrocyclic amphiphile, where the fluorescence and photoactivity of PS were completely annihilated by the complexation of macrocyclic receptor (OFF state). When nanocarriers were accumulated into tumor tissues via the enhanced permeability and retention effect, the overexpressed biomarker adenosine triphosphates displaced PSs, accompanied by their fluorescence and photoactivity recovered (ON state). These reinstallations are unattainable in normal tissues, allowing us to concurrently achieve selective tumor imaging and targeted therapy in vivo. Compared with widely used covalent approach, the present BDA strategy provides the following advantages: (1) employment of approved PSs without custom covalent decoration; (2) traceless release of PSs with high fidelity by biomarker displacement; (3) adaptability to different PSs for establishing a universal platform and promised facile combination of diverse PSs to enhance photon utility in light window. Such a host–guest BDA strategy is easily amenable to other ensembles and targets, so that versatile biomedical applications can be envisaged

Self-Assembling Peptide of d‑Amino Acids Boosts Selectivity and Antitumor Efficacy of 10-Hydroxycamptothecin

d-peptides, which consist of d-amino acids and can resist the hydrolysis catalyzed by endogenous peptidases, are one of the promising candidates for construction of peptide materials with enhanced biostability in vivo. In this paper, we report on a self-assembling supramolecular nanostructure of d-amino acid-based peptide Nap-G^DF^DF^DYGRGD (d-fiber, ^DF meant d-phenylalanine, ^DY meant d-tyrosine), which were used as carriers for 10-hydroxycamptothecin (HCPT). Transmission electron microscopy observations demonstrated the filamentous morphology of the HCPT-loaded peptides (d-fiber-HCPT). The better selectivity and antitumor activity of d-fiber-HCPT than l-fiber-HCPT were found in the in vitro and in vivo antitumor studies. These results highlight that this model d-fiber system holds great promise as vehicles of hydrophobic drugs for cancer therapy

Highly Stable Organic Small Molecular Nanoparticles as an Advanced and Biocompatible Phototheranostic Agent of Tumor in Living Mice

Near-infrared (NIR)-absorbing organic small molecules hold great promise as the phototheranostic agents for clinical translation by virtue of their intrinsic advantages such as well-defined chemical structure, high purity, and good reproducibility. However, most of the currently available ones face the challenges in varying degrees in terms of photothermal instability, and photobleaching/reactive oxygen nitrogen species (RONS) inresistance, which indeed impair their practical applications in precise diagnosis and treatment of diseases. Herein, we developed highly stable and biocompatible organic nanoparticles (ONPs) for effective phototheranostic application by design and synthesis of an organic small molecule (namely TPA-T-TQ) with intensive absorption in the NIR window. The TPA-T-TQ ONPs with no noticeable <i>in vivo</i> toxicity possess better capacities in photothermal conversion and photoacoustic imaging (PAI), as well as show far higher stabilities including thermal/photothermal stabilities, and photobleaching/RONS resistances, when compared with the clinically popularly used indocyanine green. Thanks to the combined merits, the ONPs can serve as an efficient probe for <i>in vivo</i> PAI in a high-contrast manner, which also significantly causes the stoppage of tumor growth in living mice through PAI-guided photothermal therapy. This study thus provides an insight into the development of advanced NIR-absorbing small molecules for practical phototheranostic applications

Controlled Fabrication of Functional Capsules Based on the Synergistic Interaction between Polyphenols and MOFs under Weak Basic Condition

Metal–organic coordination materials with controllable nanostructures are of widespread interest due to the coupled benefits of inorganic/organic building blocks and desired architectures. In this work, based on the finding of a synergistic interaction between metal–organic frameworks (MOFs) and natural polyphenols under weak basic condition, a facile strategy has been developed for directly fabricating diverse phenolic-inspired functional materials or metal-phenolic frameworks (MPFs) with controlled hollow nanostructures (polyhedral core–shell, rattle-like, hollow cage, etc.) and controllable size, morphology, and roughness, as well as composition. By further incorporating the diverse functionalities of polyphenols such as low toxicity and therapeutic properties, catalytic activity, and ability to serve as carbon precursors, into the novel assemblies, diverse artificially designed nanoarchitectures with target functionalities have been generated for an array of applications