Polyamidoamine Dendrimer Microgels: Hierarchical Arrangement of Dendrimers into Micrometer Domains with Expanded Structural Features for Programmable Drug Delivery and Release

Localized Sustained Release of Copper Enhances Antitumor Effects of Disulfiram in Head and Neck Cancer

Drug repurposing uses approved drugs as candidate anticancer therapeutics, harnesses previous research and development efforts, and benefits from available clinically suitable formulations and evidence of patient tolerability. In this work, the drug used clinically to treat chronic alcoholism, disulfiram (DSF), was studied for its antitumor efficacy in a copper-dependent manner. The combination of DSF and copper could achieve a tumor cell growth inhibition effect comparable to those of 5-fluorouracil and taxol on head and neck cancer cells. Both bulk dendrimer hydrogel and microsized dendrimer hydrogel particles were utilized for the localized sustained release of copper in the tumor site. The localized sustained release of copper facilitated the tumor inhibition effect following intratumoral injection in a mouse's head and neck cancer model.

Research Status of Dendrimer Micelles in Tumor Therapy for Drug Delivery

Dendrimers are a family of polymers with highly branched structure, well-defined composition, and extensive functional groups, which have attracted great attention in biomedical applications. Micelles formed by dendrimers are ideal nanocarriers for delivering anticancer agents due to the explicit study of their characteristics of particle size, charge, and biological properties such as toxicity, blood circulation time, biodistribution, and cellular internalization. Here, the classification, preparation, and structure of dendrimer micelles are reviewed, and the specific functional groups modified on the surface of dendrimers for tumor active targeting, stimuli-responsive drug release, reduced toxicity, and prolonged blood circulation time are discussed. In addition, their applications are summarized as various platforms for biomedical applications related to cancer therapy including drug delivery, gene transfection, nano-contrast for imaging, and combined therapy. Other applications such as tissue engineering and biosensor are also involved. Finally, the possible challenges and perspectives of dendrimer micelles for their further applications are discussed.

A Biomimetic Nanogel System Restores Macrophage Phagocytosis for Magnetic Resonance Imaging-Guided Synergistic Chemoimmunotherapy of Breast Cancer

Novel strategies to facilitate tumor-specific drug delivery and restore immune attacks remain to be developed to overcome the current limitations of chemotherapy. Herein, a cancer cell membrane (CM)-camouflaged and ultrasmall iron oxide nanoparticles (USIO NPs)-loaded polyethylenimine nanogel (NG) system is reported to co-deliver docetaxel (DTX) and CD47 siRNA (siCD47). The prepared co-delivery system exhibits good colloidal stability, biocompatibility, and r1 relaxivity (1.35 mM-1 s-1 ) and enables redox-responsive release of the loaded DTX in the tumor microenvironment. The NG system realizes homologous targeting delivery of DTX and siCD47 to murine breast cancer cells (4T1 cells) for efficient chemotherapy and gene silencing; thus, inducing immunogenic cell death (ICD) and restoring macrophage phagocytic effect through downregulation of "don't eat me" signals on cancer cells. Likewise, the co-delivery system can also act on macrophages to promote their M1 polarization, which can be combined with DTX-mediated ICD and antibody-mediated immune checkpoint blockade to generate effector T cells for robust chemoimmunotherapy. Further, the USIO NPs-incorporated NG system also allows for magnetic resonance imaging of tumors. The developed biomimetic NG system acting on both cancer cells and macrophages holds a promising potential for macrophage phagocytosis-restored chemoimmunotherapy.

Dendrimer and dendrimer gel-derived drug delivery systems: Breaking bottlenecks of topical administration of glaucoma medications

Due to high structural flexibility, multidrug carrying capability, and tunable size, dendrimers have been used as suitable carriers for ophthalmic drug delivery. Drug molecules can be either encapsulated or chemically coupled to dendrimers. The nanoscopic size, spheroidal shape, and cationic surface of polyamidoamine (PAMAM) dendrimers promote their interaction with the cornea and result in prolonged precorneal retention. Dendrimers could be further cross-linked to produce three-dimensional hydrogel networks or dendrimer hydrogels (DH). The properties of the DH can be readily adjusted to maintain both fluidity and adhesiveness, making them suitable for developing topical ocular drug formulations. Micro-/nano-sized DHs, that is, dendrimer micro-/nano-gels, have unique properties such as ease of administration, large specific surface area for adhesion, and drug targeting functionalities, making them attractive for ophthalmic drug delivery. This perspective reports advances in PAMAM dendrimer based drug delivery systems including drug conjugates and micro- and nano-gels to enhance and sustain the delivery of multiple anti-glaucoma drugs, Dendrimer and dendrimer gel-derived drug delivery systems hold great potential as multifunctional topical drug delivery systems for the eye.

Multifunctional Low-Generation Dendrimer Nanogels as an Emerging Probe for Tumor-Specific CT/MR Dual-Modal Imaging

The development of nanoprobes that have amplified enhanced permeability and retention (EPR) effect is crucial for their precise cancer diagnosis performance. Here, we present the development of functional dendrimer-based nanogels (DNGs) with the generation three primary amine-terminated poly(amidoamine) (PAMAM) dendrimers (G3·NH₂) cross-linked by N,N'-bis(acryloyl) cystamine (BAC). The DNGs were prepared through a Michael addition reaction between G3·NH₂ dendrimers and BAC via an inverse microemulsion method and entrapped with gold nanoparticles (Au NPs) to form Au-DNGs. The Au-DNGs were sequentially modified with diethylenetriamine penta-acetic acid (DTPA)-gadolinium (Gd) complex, poly(ethylene glycol) (PEG)-linked arginine-glycine-aspartic (RGD) peptide, and 1,3-propanesultone (1,3-PS). The formed multifunctional RGD-Gd@Au-DNGs-PS (R-G@ADP) possessing an average diameter of 122 nm are colloidally stable and display a high X-ray attenuation coefficient, excellent r₁ relaxivity (9.13 mM^-1 s^-1), desired protein resistance rendered by the zwitterionic modification, and cytocompatibility. With the targeting specificity mediated by RGD and the much better tumor penetration capability than the counterpart material of single dendrimer-entrapped Au NPs, the developed multifunctional R-G@ADP enable targeted and enhanced computed tomography (CT)/magnetic resonance (MR) dual-modal imaging of a pancreatic tumor model in vivo. The current work demonstrates a unique design of targeted and zwitterionic DNGs with prolonged blood circulation time as an emerging nanoprobe for specific tumor CT/MR imaging through amplified passive EPR effect.

Dendrimer-based drug delivery systems: history, challenges, and latest developments

Since the first dendrimer was reported in 1978 by Fritz Vögtle, dendrimer research has grown exponentially, from synthesis to application in the past four decades. The distinct structure characteristics of dendrimers include nanoscopic size, multi-functionalized surface, high branching, cavernous interior, and so on, making dendrimers themselves ideal drug delivery vehicles. This mini review article provides a brief overview of dendrimer’s history and properties and the latest developments of dendrimers as drug delivery systems. This review focuses on the latest progress in the applications of dendrimers as drug and gene carriers, including 1) active drug release strategies to dissociate drug/gene from dendrimer in response to stimuli; 2) size-adaptive and charge reversal dendrimer delivery systems that can better take advantage of the size and surface properties of dendrimer; 3) bulk and micro/nano dendrimer gel delivery systems. The recent advances in dendrimer formulations may lead to the generation of new drug and gene products and enable the development of novel combination therapies.

Recent Updates on Supramolecular-Based Drug Delivery - Macrocycles and Supramolecular Gels

Supramolecules-based drug delivery has attracted significant recent research attention as it could enhance drug solubility, retention time, targeting, and stimuli responsiveness. Among the different supramolecules and assemblies, the macrocycles and the supramolecular hydrogels are the two important categories investigated to a greater extent. Here, we provide the most recent advancements in these categories. Under macrocycles, reports on drug delivery by cyclodextrins, cucurbiturils, calixarenes/pillararenes, crown ethers and porphyrins are detailed. The second category discusses the supramolecular hydrogels of macrocycles/polymers and low molecular weight gelators. The updated information provided could be helpful to advance R & D in this vital area.

Multiparametric Material Functionality of Microtissue-Based In Vitro Models as Alternatives to Animal Testing

With the definition of the 3R principle by Russel and Burch in 1959, the search for an adequate substitute for animal testing has become one of the most important tasks and challenges of this time, not only from an ethical, but also from a scientific, economic, and legal point of view. Microtissue-based in vitro model systems offer a valuable approach to address this issue by accounting for the complexity of natural tissues in a simplified manner. To increase the functionality of these model systems and thus make their use as a substitute for animal testing more likely in the future, the fundamentals need to be continuously improved. Corresponding requirements exist in the development of multifunctional, hydrogel-based materials, whose properties are considered in this review under the aspects of processability, adaptivity, biocompatibility, and stability/degradability.

Nanocarrier-hydrogel composite delivery systems for precision drug release

Hydrogels are a class of biomaterials widely implemented in medical applications due to their biocompatibility and biodegradability. Despite the many successes of hydrogel-based delivery systems, there remain challenges to hydrogel drug delivery such as a burst release at the time of administration, a limited ability to encapsulate certain types of drugs (i.e., hydrophobic drugs, proteins, antibodies, and nucleic acids), and poor tunability of geometry and shape for controlled drug release. This review discusses two main important advances in hydrogel fabrication for precision drug release: first, the incorporation of nanocarriers to diversify their drug loading capability, and second, the design of hydrogels using 3D printing to precisely control drug dosing and release kinetics via high-resolution structures and geometries. We also outline ongoing challenges and discuss opportunities to further optimize drug release from hydrogels for personalized medicine. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Delivery of therapeutic oligonucleotides in nanoscale

Therapeutic oligonucleotides (TOs) represent one of the most promising drug candidates in the targeted cancer treatment due to their high specificity and capability of modulating cellular pathways that are not readily druggable. However, efficiently delivering of TOs to cancer cellular targets is still the biggest challenge in promoting their clinical translations. Emerging as a significant drug delivery vector, nanoparticles (NPs) can not only protect TOs from nuclease degradation and enhance their tumor accumulation, but also can improve the cell uptake efficiency of TOs as well as the following endosomal escape to increase the therapeutic index. Furthermore, targeted and on-demand drug release of TOs can also be approached to minimize the risk of toxicity towards normal tissues using stimuli-responsive NPs. In the past decades, remarkable progresses have been made on the TOs delivery based on various NPs with specific purposes. In this review, we will first give a brief introduction on the basis of TOs as well as the action mechanisms of several typical TOs, and then describe the obstacles that prevent the clinical translation of TOs, followed by a comprehensive overview of the recent progresses on TOs delivery based on several various types of nanocarriers containing lipid-based nanoparticles, polymeric nanoparticles, gold nanoparticles, porous nanoparticles, DNA/RNA nanoassembly, extracellular vesicles, and imaging-guided drug delivery nanoparticles.

Nano-in-Nano Dendrimer Gel Particles for Efficient Topical Delivery of Antiglaucoma Drugs into the Eye

Low bioavailability of topically applied drugs remains a significant challenge for long-term glaucoma therapy. To enhance drug delivery efficiency, we developed dendrimer gel particles that collectively exhibit structural benefits of dendrimer, hydrogel, and particles, using the inverse emulsion method coupled with the highly efficient aza-Michael addition reaction (IEaMA). This hierarchical approach would maximize the utility of the structural features of existing ocular drug delivery systems. We have tested the delivery efficiency and efficacy of two first-line antiglaucoma drugs, brimonidine tartrate (BT) and timolol maleate (TM), which were loaded into dendrimer gel particles of various sizes, i.e., nDHP (nano-in-nano dendrimer hydrogel particles, ~200 nm), μDHP3 (3 μm), and μDHP10 (9 μm). We found that nDHP was superior to μDHP3 and μDHP10 in terms of cytocompatibility, degradability, drug release kinetics, and corneal permeability. The nDHPs increased drug corneal permeability by 17-fold compared to plain drug solution and enabled zero-order prolonged drug release kinetics. The nDHP-based formulation demonstrated pronounced IOP-lowering effects in both single-dose test and 7-day chronic daily dosing test in both Brown Norway rats and glaucoma mice. Taken together, we have developed nano-in-nano dendrimer gel particles for precise dosing and enabling sustained and synergistic efficacy of antiglaucoma drugs, which could be clinically impactful for improving glaucoma treatment.

Complexation of Injectable Biphasic Calcium Phosphate with Phosphoserine-Presenting Dendrons with Enhanced Osteoregenerative Properties

Injectable biphasic calcium phosphates have been proposed as a solution in the treatment of a range of clinical applications including as fillers in the augmentation of osteoporotic bone. To date, various biodegradable natural or synthetic organics have been used as a polymer component of bone materials to increase their cohesiveness. Herein, a novel bone material was developed combining osteoconductive biphasic calcium phosphate (BCP) nanoparticles with phosphoserine-tethered generation 3 poly(epsilon-lysine) dendron (G3-K PS), a class of hyperbranched peptides previously shown to induce biomineralization and stem cell osteogenic differentiation. Strontium was also incorporated into the BCP nanocrystals (SrBCP) to prevent bone resorption. Within 24 h, an antiwashout behavior was observed in G3-K PS-integrated pure BCP group (BCPG3). Moreover, both in vitro tests by relevant cell phenotypes and an in vivo tissue regeneration study by an osteoporotic animal bone implantation showed that the integration of G3-K PS would downregulate Cxcl9 gene and protein expressions, thus enhancing bone regeneration measured as bone mineral density, new bone volume ratio, and trabecular microarchitectural parameters. However, no synergistic effect was found when Sr was incorporated into the BCPG3 bone pastes. Notably, results indicated a concomitant reduction of bone regeneration potential assessed as reduced Runx2 and PINP expression when bone resorptive RANKL and CTX-I levels were reduced by Sr supplementation. Altogether, the results suggest the potential of injectable BCPG3 bone materials in the treatment of osteoporotic bone defects.

Dendritic Effects of Injectable Biodegradable Thermogels on Pharmacotherapy of Inflammatory Glaucoma-Associated Degradation of Extracellular Matrix

The development of advanced drug delivery systems with extensively sustained release and multiple functions is highly imperative for effective attenuation of the degradation of ocular extracellular matrix that is associated with inflammatory glaucoma. Here, the generation of amine-terminated polyamidoamine dendrimers in an injectable biodegradable thermogel is demonstrated to be important for achieving prolonged drug release profiles and potent anti-inflammatory effects. Among various generations (Gx, x = 0, 1, 3, 5), third-generation G3 is proved as the most effective material for optimizing the synergistic effects of gelatin and poly(N-isopropylacrylamide) and generating a thermogel with the highest biodegradation resistance, the best drug encapsulation/extended-release performance, and the best ability to reduce the elevated expression of inflammatory molecules. A pharmacotherapy based on intracameral injection of thermogels coloaded with pilocarpine and ascorbic acid results in effective alleviation of progressive glaucoma owing to the anti-inflammatory activity and long-acting drug release (above a therapeutic level of 10 µg mL^-1 over 80 days) of thermogels, which simultaneously suppress inflammation and stimulate regeneration of stromal collagen and retinal laminin. These findings on the dendritic effects of rationally designed injectable biomaterials with potent anti-inflammatory effects and controlled drug release demonstrate great promise of their use for pharmacological treatment of progressive glaucoma.

Drug-Conjugated Dendrimer Hydrogel Enables Sustained Drug Release via a Self-Cleaving Mechanism

In this study, the anticancer drug, camptothecin (CPT), was covalently grafted onto polyamidoamine (PAMAM) dendrimer surface and then reacted with polyethylene glycol diacrylate (PEG-DA) to form dendrimer hydrogel (DH-G3-CPT) with low cross-linking density. In this novel drug delivery system, CPT was cleaved from dendrimer via the ammonolysis of ester bonds and then diffused out of the hydrogel network, thus leading to significantly prolonged drug release. The self-cleaving release kinetics of camptothecin can be further tuned by pH. This DH-G3-CPT drug delivery system has both injectability and sustained drug release. It showed an excellent tumor inhibition effect following intratumoral injection in a head and neck cancer model of mouse.

Triply responsive coumarin-based microgels with remarkably large photo-switchable swelling

Using two different wavelengths of UV light enables remarkably strong photo-switchable swelling of pH- and temperature-responsive microgels and photo-release of doxorubicin.

Fabrication of zwitterionic and pH-responsive polyacetal dendrimers for anticancer drug delivery

A zwitterionic sulfobetaine functionalized polyacetal dendrimer presented excellent structural stability, high internalization efficiency, unique pH-responsive drug release behaviors and remarkable antitumor efficacy.

Glycerol-Silicone Elastomers as Active Matrices with Controllable Release Profiles

Drug release regimes must be controlled for the optimal therapeutic effect. Although it is relatively straightforward to create first-order release matrices, it can be challenging to avoid an initial burst. Matrices with zero-order profiles are perceived to be beneficial in many cases but are even more difficult to formulate. We describe the straightforward synthesis of elastomeric composites prepared from silicone in which the active substance is dispersed in glycerol. The release of glycerol-soluble actives from the films of these materials was shown to be tunable with respect to the order of release (zero- or first-order) simply by changing the glycerol content. Importantly, release from the elastomers showed no burst effect. The discrete glycerol domains embedded within a silicone matrix act as reservoirs for active substances. Upon contact with aqueous media, the active substances are released from the matrices exhibiting zero-order, near zero-order, or first-order release kinetics. Various parameters that could influence the release process, including glycerol content, glycerol domain size, or membrane thickness, are thoroughly investigated, elucidating guidelines for creating matrices capable of delivering the active substances at desired rates. Additionally, the composites proved to absorb significant amounts of liquid water (up to 1850% of sample mass), a feature that can be tuned by the manipulation of the composite structure.