Modular Self-Assembling Dendrimer Nanosystems for Magnetic Resonance and Multimodality Imaging of Tumors.

Bioimaging is a powerful tool for diagnosing tumors but remains limited in terms of sensitivity and specificity. Nanotechnology-based imaging probes able to accommodate abundant imaging units with different imaging modalities are particularly promising for overcoming these limitations. In addition, the nanosized imaging agents can specifically increase the contrast of tumors by exploiting the enhanced permeability and retention effect. A proof-of-concept study is performed on pancreatic cancer to demonstrate the use of modular amphiphilic dendrimer-based nanoprobes for magnetic resonance (MR) imaging (MRI) or MR/near-infrared fluorescence (NIRF) multimodality imaging. Specifically, the self-assembly of an amphiphilic dendrimer bearing multiple Gd3+ units at its terminals, generates a nanomicellar agent exhibiting favorable relaxivity for MRI with a good safety profile. MRI reveals an up to two-fold higher contrast enhancement in tumors than in normal muscle. Encapsulating the NIRF dye within the core of the nanoprobe yields an MR/NIRF bimodal imaging agent for tumor detection that is efficient both for MRI, at Gd3+ concentrations 1/10 the standard clinical dose, and for NIRF imaging, allowing over two-fold stronger fluorescence intensities. These self-assembling dendrimer nanosystems thus constitute effective probes for MRI and MR/NIRF multimodality imaging, offering a promising nanotechnology platform for elaborating multimodality imaging probes in biomedical applications.

Dendrimer nanosystems for adaptive tumor-assisted drug delivery via extracellular vesicle hijacking.

Drug delivery systems (DDSs) that can overcome tumor heterogeneity and achieve deep tumor penetration are challenging to develop yet in high demand for cancer treatment. We report here a DDS based on self-assembling dendrimer nanomicelles for effective and deep tumor penetration via in situ tumor-secreted extracellular vesicles (EVs), an endogenous transport system that evolves with tumor microenvironment. Upon arrival at a tumor, these dendrimer nanomicelles had their payload repackaged by the cells into EVs, which were further transported and internalized by other cells for delivery "in relay." Using pancreatic and colorectal cancer-derived 2D, 3D, and xenograft models, we demonstrated that the in situ-generated EVs mediated intercellular delivery, propagating cargo from cell to cell and deep within the tumor. Our study provides a new perspective on exploiting the intrinsic features of tumors alongside dendrimer supramolecular chemistry to develop smart and effective DDSs to overcome tumor heterogeneity and their evolutive nature thereby improving cancer therapy.

Dynamic self-assembling supramolecular dendrimer nanosystems as potent antibacterial candidates against drug-resistant bacteria and biofilms.

The alarming and prevailing antibiotic resistance crisis urgently calls for innovative "outside of the box" antibacterial agents, which can differ substantially from conventional antibiotics. In this context, we have established antibacterial candidates based on dynamic supramolecular dendrimer nanosystems self-assembled with amphiphilic dendrimers composed of a long hydrophobic alkyl chain and a small hydrophilic poly(amidoamine) dendron bearing distinct terminal functionalities. Remarkably, the amphiphilic dendrimer with amine terminals exhibited strong antibacterial activity against both Gram-positive and Gram-negative as well as drug-resistant bacteria, and prevented biofilm formation. Multidisciplinary studies combining experimental approaches and computer modelling together demonstrate that the dendrimer interacts and binds via electrostatic interactions with the bacterial membrane, where it becomes enriched and then dynamically self-assembles into supramolecular nanoassemblies for stronger and multivalent interactions. These, in turn, rapidly promote the insertion of the hydrophobic dendrimer tail into the bacterial membrane thereby inducing bacterial cell lysis and constituting powerful antibacterial activity. Our study presents a novel concept for creating nanotechnology-based antibacterial candidates via dynamic self-assembly and offers a new perspective for combatting recalcitrant bacterial infection.

Benzothiazole Amides as TRPC3/6 Inhibitors for Gastric Cancer Treatment.

Transient receptor potential canonical channel 6 (TRPC6) has been implicated in many kinds of malignant tumors, but very few potent TRPC6 antagonists are available. In this study, a benzothiazole amide derivative 1a was discovered as a TRPC6 activator in a cell-based high-throughput screening. A series of benzothiazole amide derivatives were designed and synthesized. The docking analyses indicated that the conformations of the compounds bound to TRPC6 determined the agonistic or antagonistic activity of the compounds against TRPC6, and compound 1s with the tetrahydronaphthalene group in R1 position fit well into the binding pocket of the antagonist-bound conformation of TRPC6. Compound 1s showed an inhibitory potency order of TRPC3 (IC50 3.3 ± 0.13 µM) ≈ C6 (IC50 4.2 ± 0.1 µM) > C7 with good anti-gastric cancer activity in a micromolecular range against AGS and MKN-45, respectively. In addition, 1s inhibited the invasion and migration of MKN-45 cells in vitro.

Self-Assembling Supramolecular Dendrimers for Biomedical Applications: Lessons Learned from Poly(amidoamine) Dendrimers.

Dendrimers, notable for their well-defined radial structures with numerous terminal functionalities, hold great promise for biomedical applications such as drug delivery, diagnostics, and therapeutics. However, their translation into clinical use has been greatly impeded by their challenging stepwise synthesis and difficult purification.To circumvent these obstacles, we have pioneered a self-assembly approach to constructing noncovalent supramolecular dendrimers using small amphiphilic dendrimer building units which can be easily synthesized and purified. By virtue of their amphipathic nature, the small amphiphilic dendrimers are able to self-assemble and generate large supramolecular dendrimers via noncovalent weak interactions such as van der Waals forces, H bonds, and electrostatic interactions. The so-created noncovalent dendrimers can mimic covalent dendrimers not only in terms of the radial structural feature emanating from a central core but also in their capacity to deliver drugs and imaging agents for biomedical applications. The noncovalent supramolecular dendrimers can be easily synthesized and modulated with regard to size, shape, and properties by varying the nature of the hydrophobic and hydrophilic entities as well as the dendrimer generation and terminal functionalities, ensuring their adaptability to specific applications. In particular, the dendritic structure of the amphiphilic building units permits the creation of large void spaces within the formed supramolecular dendrimers for the physical encapsulation of drugs, while the large number of surface functionalities can be exploited for both physical and chemical conjugation of pharmaceutic agents for drug delivery.Poly(amidoamine) (PAMAM) dendrimers are the most intensively studied for biomedical applications by virtue of their excellent biocompatibility imparted by their peptide-mimicking amide backbones and numerous interior and terminal amine functionalities. We present a short overview of our self-assembly strategy for constructing supramolecular PAMAM dendrimers for biomedical applications. Specifically, we start with the introduction of dendrimers and their synthesis, focusing on the innovative self-assembly synthesis of supramolecular dendrimers. We then detail the representative examples of the noncovalent supramolecular PAMAM dendrimers established in our group for the delivery of anticancer drugs, nucleic acid therapeutics, and imaging agents, either within the dendrimer interior or at the dendrimer terminals on the surface. Some of the supramolecular dendrimer nanosystems exhibit outstanding performance, excelling the corresponding clinical anticancer therapeutics and imaging agents. This self-assembly approach to creating supramolecular dendrimers is completely novel in concept yet easy to implement in practice, offering a fresh perspective for exploiting the advantageous features of dendrimers in biomedical applications.

Surface Charge of Supramolecular Nanosystems for In Vivo Biodistribution: A MicroSPECT/CT Imaging Study.

Bioimaging has revolutionized medicine by providing accurate information for disease diagnosis and treatment. Nanotechnology-based bioimaging is expected to further improve imaging sensitivity and specificity. In this context, supramolecular nanosystems based on self-assembly of amphiphilic dendrimers for single photon emission computed tomography (SPECT) bioimaging are developed. These dendrimers bear multiple In3+ radionuclides at their terminals as SPECT reporters. By replacing the macrocyclic 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid cage with the smaller 1,4,7-triazacyclononane-1,4,7-triacetic acid scaffold as the In3+ chelator, the corresponding dendrimer exhibits neutral In3+ -complex terminals in place of negatively charged In3+ -complex terminals. This negative-to-neutral surface charge alteration completely reverses the zeta-potential of the nanosystems from negative to positive. As a consequence, the resulting SPECT nanoprobe generates a highly sought-after biodistribution profile accompanied by a drastically reduced uptake in liver, leading to significantly improved tumor imaging. This finding contrasts with current literature reporting that positively charged nanoparticles have preferential accumulation in the liver. As such, this study provides new perspectives for improving the biodistribution of positively charged nanosystems for biomedical applications.

A self-assembling amphiphilic dendrimer nanotracer for SPECT imaging.

Bioimaging has revolutionized modern medicine, and nanotechnology can offer further specific and sensitive imaging. We report here an amphiphilic dendrimer able to self-assemble into supramolecular nanomicelles for effective tumor detection using SPECT radioimaging. This highlights the promising potential of supramolecular dendrimer platforms for biomedical imaging.

Self-assembling supramolecular dendrimer nanosystem for PET imaging of tumors.

Bioimaging plays an important role in cancer diagnosis and treatment. However, imaging sensitivity and specificity still constitute key challenges. Nanotechnology-based imaging is particularly promising for overcoming these limitations because nanosized imaging agents can specifically home in on tumors via the "enhanced permeation and retention" (EPR) effect, thus resulting in enhanced imaging sensitivity and specificity. Here, we report an original nanosystem for positron emission tomography (PET) imaging based on an amphiphilic dendrimer, which bears multiple PET reporting units at the terminals. This dendrimer is able to self-assemble into small and uniform nanomicelles, which accumulate in tumors for effective PET imaging. Benefiting from the combined dendrimeric multivalence and EPR-mediated passive tumor targeting, this nanosystem demonstrates superior imaging sensitivity and specificity, with up to 14-fold increased PET signal ratios compared with the clinical gold reference 2-fluorodeoxyglucose ([18F]FDG). Most importantly, this dendrimer system can detect imaging-refractory low-glucose-uptake tumors that are otherwise undetectable using [18F]FDG. In addition, it is endowed with an excellent safety profile and favorable pharmacokinetics for PET imaging. Consequently, this dendrimer nanosystem constitutes an effective and promising approach for cancer imaging. Our study also demonstrates that nanotechnology based on self-assembling dendrimers provides a fresh perspective for biomedical imaging and cancer diagnosis.

Facile Cu(ii)-mediated conjugation of thioesters and thioacids to peptides and proteins under mild conditions.

The bioconjugation of peptide derivatives such as polypeptides, peptide-based probes and proteins is a vibrant area in many scientific fields. However, reports on metal-mediated chemical methods towards native peptides especially non-engineering protein modification under mild conditions are still limited. Herein, we describe a novel Cu(ii)-mediated strategy for the conjugation of thioesters/thioacids to peptides under mild conditions with high functional group tolerance. Based on this strategy, polypeptides, even peptide-based fluorescent probes, can be efficiently constructed. Finally, the selective modification of lysine residues of native Ub with thioesters could be realized and complete conjugation of Ub could be achieved even under equivalent Cu(ii). These promising results could greatly expand Cu(ii)-mediated reaction strategies on chemical biology and molecular imaging.