Nanoscale drug delivery systems for cancer treatment have demonstrated promising results in enhancing the selectivity of therapeutic agents while reducing their toxic side effects. However, several biological and physical barriers, such as the immunogenicity and undesirable biodistributions of such delivery systems, have hindered their fast translation. To address these issues, we have developed an exosome−dendrimer hybrid nanoparticle (NP) platform to combine the advantageous biological properties of natural exosomes and synthetic dendrimers into a single NP system. The novel hybrid NPs, consisting of exosomes derived from MCF7 cells and functionalized poly-(amidoamine) (PAMAM) dendrimers, were prepared using sonication and characterized in terms of loading efficiency, size, cytotoxicity, and cellular interactions. Our results indicate that the loading of dendrimers into exosomes is dependent on dendrimer size and charge. The hybrid NPs inherited the size (∼150 nm), surface charge (−10 mV), and surface protein markers (CD81 and CD63) of exosomes. Importantly, the hybrid NPs enhanced the cellular internalization of amine-terminated PAMAM dendrimers (p < 0.05) while exhibiting substantially lower cytotoxicity than the free positively charged dendrimers (113.3 vs 35.6% of cell viability at 500 nM, p < 0.05). These advantageous properties of hybrid NPs were leveraged for use as a gene delivery vehicle, resulting in enhanced oligonucleotide delivery (over 2-fold) to cancer cells, compared to dendrimers alone. Furthermore, the hybrid NPs effectively delivered small interfering RNA (siRNA) as well, downregulating programmed death-ligand 1 (PD-L1) expression significantly more (3.8-fold) than dendrimers alone (p < 0.05). Our results demonstrate that the individual characteristics of both exosomes and dendrimers can be integrated to generate a multifaceted NP platform, proposing a novel NP design strategy.

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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.

Nanoparticle-based drug delivery systems have been designed to treat various diseases. However, many problems remain, such as inadequate tumor targeting and poor therapeutic outcomes. To overcome these obstacles, cell-based drug delivery systems have been developed. Candidates for cell-mediated drug delivery include blood cells, immune cells, and stem cells with innate tumor tropism and low immunogenicity; they act as a disguise to deliver the therapeutic payload. In drug delivery systems, therapeutic agents are encapsulated intracellularly or attached to the surface of the plasma membrane and transported to the desired site. Here, we review the pros and cons of cell-based therapies and discuss their homing mechanisms in the tumor microenvironment. In addition, different strategies to load therapeutic agents inside or on the surface of circulating cells and the current applications for a wide range of disease treatments are summarized.