A Biodegradable and Amphiphilic Linear-Dendritic Copolymer as a Drug Carrier Platform for Intracellular Drug Delivery

Dendritic-Linear Copolymer and Dendron Lipid Nanoparticles for Drug and Gene Delivery

Polymers constitute a diverse class of macromolecules that have demonstrated their unique advantages to be utilized for drug or gene delivery applications. In particular, polymers with a highly ordered, hyperbranched structure─"dendrons"─offer significant benefits to the design of such nanomedicines. The incorporation of dendrons into block copolymer micelles can endow various unique properties that are not typically observed from linear polymer counterparts. Specifically, the dendritic structure induces the conical shape of unimers that form micelles, thereby improving the thermodynamic stability and achieving a low critical micelle concentration (CMC). Furthermore, through a high density of highly ordered functional groups, dendrons can enhance gene complexation, drug loading, and stimuli-responsive behavior. In addition, outward-branching dendrons can support a high density of nonfouling polymers, such as poly(ethylene glycol), for serum stability and variable densities of multifunctional groups for multivalent cellular targeting and interactions. In this paper, we review the design considerations for dendron-lipid nanoparticles and dendron micelles formed from amphiphilic block copolymers intended for gene transfection and cancer drug delivery applications. These technologies are early in preclinical development and, as with other nanomedicines, face many obstacles on the way to clinical adoption. Nevertheless, the utility of dendron micelles for drug delivery remains relatively underexplored, and we believe there are significant and dramatic advancements to be made in tumor targeting with these platforms.

Simple and Efficient Synthesis of Functionalized Cyclic Carbonate Monomers Using Carbon Dioxide

Aliphatic polycarbonates represent an important class of materials with diverse applications ranging from battery electrolytes, polyurethane intermediates, and materials for biomedical applications. These materials can be produced via the ring-opening polymerization (ROP) of six- to eight-membered cyclic carbonates derived from precursor 1,3- and 1,5-diols. These diols can contain a range of functional groups depending on the desired thermal, mechanical, and solution properties. Generally, the ring closure to form the cyclic carbonate requires the use of undesirable and hazardous reagents. Advances in synthetic methodologies and catalysis have enabled the use of carbon dioxide (CO₂) to perform these transformations with a high conversion of diol to cyclic carbonate, yet modest isolated yields due to oligomerization side reactions. In this Letter, we evaluate a series of bases in the presence of p-toluenesulfonyl chloride and the appropriate diol to better understand their effect on the yield and presence of oligomer byproducts during cyclic carbonate formation from CO₂. From this study, N,N-tetramethylethylenediamine (TMEDA) was identified as an optimal base, facilitating the preparation of a diverse array of both six- and eight-membered carbonates from CO₂ within 10 to 15 min. The robust conditions for both, the preparation of the diol precursor, and the TMEDA-mediated carbonate synthesis enabled readily telescoping the two-step reaction sequence, greatly simplifying the process of monomer preparation.

Evaluation of pH-dependent amphiphilic carbosilane dendrons in micelle formation, drug loading and HIV-1 infection

New amphiphilic carbosilane dendrons with pH-dependent behaviour based on the presence of carboxylate (propionate or succinate) groups at their peripheries and a fatty acid at the focal point were developed. In the presence of salts, they were able to form micelles with critical aggregation concentrations increasing with increasing dendron generation. Their thermodynamic parameters were calculated from surface tension measurements and their diameters at different pHs were measured by dynamic light scattering. These micelles were stable at basic pH but degraded under acidic conditions. No significant differences were found for the propionate and succinate based dendron micelles at basic or acidic pH, but the succinate dendron assemblies were more stable at neutral pH. The properties of these systems as drug nano-carriers were studied using both hydrophilic and hydrophobic molecules, and the drug loading varied with the structure and charge of the drug. In addition, due to the presence of multiple negative charges, the dendrons exhibited anti-HIV activity. Higher generation dendrons with more peripheral carboxylates that were not assembled into micelles were more active than micelles composed of lower generation dendrons having fewer peripheral carboxylates.

Redox-responsive hyaluronic acid nanogels for hyperthermia- assisted chemotherapy to overcome multidrug resistance

Although chemotherapy has been widely used in the treatment of many kinds of cancer, drug resistance and side effects are the main obstacles in the cancer chemotherapy that result in an inferior therapeutic outcome. For the design of drug delivery system, extracellular stability and intracellular effective release are also a pair of contradictions. In this research, gold nanorods (AuNRs) loaded hyaluronic acid (HA) nanogels with reduction sensitivity were prepared for the efficient intracellular delivery of doxorubicin (DOX). The aforementioned HA-CysNG@AuNR nanogels with cystamine (Cys) as crosslinker could remain stable in the physiological condition and release DOX rapidly in the mimic intracellular glutathione (GSH) condition. Meanwhile, the cellular uptake efficiency by the human breast carcinoma (MCF-7) cells was enhanced because of the highly expressed HA receptor (CD44) on the cytomembrane. However, further cell experiments verified that it was difficult to achieve desired results for drug-resistant human breast cancer (MCF-7 ADR) cells due to the reduced drug uptake and enhanced drug efflux. Interestingly, this multidrug resistance of MCF-7 ADR cells could be reversed after treated with near-infrared (NIR) light. This might ascribe to the hyperthermia generated by AuNRs under NIR, which suspended drug efflux process and led to excellent hyperthermia-assisted chemotherapy outcome. Overall, our studies suggested that AuNRs loaded reduction-sensitive HA nanogels were excellent candidates of drug carriers to reverse the drug-resistance and induce severe apoptosis of drug-resistant MCF-7 ADR cells.

Drug Delivery Systems from Self-Assembly of Dendron-Polymer Conjugates †

This review highlights the utilization of dendron-polymer conjugates as building blocks for the fabrication of nanosized drug delivery vehicles. The examples given provide an overview of the evolution of these delivery platforms, from simple micellar containers to smart stimuli- responsive drug delivery systems through their design at the macromolecular level. Variations in chemical composition and connectivity of the dendritic and polymeric segments provide a variety of self-assembled micellar nanostructures that embody desirable attributes of viable drug delivery systems.

A biomimetic fluorescent chemosensor for highly sensitive zinc(ii) detection and its application for cell imaging

To fabricate a novel biomimetic fluorescent chemosensor, PSaAEMA-co-PMPC was synthesized via atom transfer radical polymerization, and this copolymer could be used for the detection of zinc(ii) and cell imaging. A series tests with various metal ions verified the specific fluorescence response behavior. This novel biomimetic fluorescent chemosensor exhibits excellent selectivity for Zn²⁺ ions over a wide range of tested metal ions in an aqueous solution. Moreover, cytotoxicity and bio-imaging tests were conducted to study the potential bio-application of the chemosensor. Owing to the biomimetic portion (phosphorylcholine), this copolymer possesses outstanding biocompatibility and could clearly image cells. The results indicated that PSaAEMA-co-PMPC has great potential for application in zinc(ii) detection and cell imaging.

To fabricate a novel biomimetic fluorescent chemosensor, PSaAEMA-co-PMPC was synthesized via atom transfer radical polymerization, and this copolymer could be used for the detection of zinc(ii) and cell imaging.

Formation and characterization of Langmuir and Langmuir-Blodgett films of Newkome-type dendrons in presence and absence of a therapeutic compound, for the development of surface mediated drug delivery systems

Organic macromolecules with dendrimeric architectures are polymeric materials potentially useful as nanocarriers for therapeutic drugs. In this work, we evaluate a series of Newkome-type dendrons in Langmuir and Langmuir-Blodgett films as platforms capable of interacting with a potential antitumoral agent. The nanocomposite is proposed as model for the development of surface mediated drug delivery systems. We were successful in the formation and characterization of pure (dendrons) and composite (drug-dendron) stable and reproducible monolayers, and their transfer to solid substrates. A detailed study of topographic characteristics of the generated surfaces by atomic force microscopy was conducted. Furthermore, we probed dendron monolayer films as anchorage surfaces for mammalian cells. Normal cell attachment and proliferation on the surfaces were observed. No evident cytotoxic effects were detected, demonstrating the adequate biocompatibility of the surfaces.