A Coarse-Grained Molecular Dynamics Description of Docetaxel-Conjugate Release from PLGA Matrices

Mechanisms and Barriers in Nanomedicine: Progress in the Field and Future Directions

In recent years, steady progress has been made in synthesizing and characterizing engineered nanoparticles, resulting in several approved drugs and multiple promising candidates in clinical trials. Regulatory agencies such as the Food and Drug Administration and the European Medicines Agency released important guidance documents facilitating nanoparticle-based drug product development, particularly in the context of liposomes and lipid-based carriers. Even with the progress achieved, it is clear that many barriers must still be overcome to accelerate translation into the clinic. At the recent conference workshop "Mechanisms and Barriers in Nanomedicine" in May 2023 in Colorado, U.S.A., leading experts discussed the formulation, physiological, immunological, regulatory, clinical, and educational barriers. This position paper invites open, unrestricted, nonproprietary discussion among senior faculty, young investigators, and students to trigger ideas and concepts to move the field forward.

Therapeutic Peptides Are Preferentially Solubilized in Specific Microenvironments within PEG-PLGA Polymer Nanoparticles

Polymeric nanoparticles are a highly promising drug delivery formulation. However, a lack of understanding of the molecular mechanisms that underlie their drug solubilization and controlled release capabilities has hindered the efficient clinical translation of such technologies. Polyethylene glycol-poly(lactic-co-glycolic) acid (PEG-PLGA) nanoparticles have been widely studied as cancer drug delivery vehicles. In this letter, we use unbiased coarse-grained molecular dynamics simulations to model the self-assembly of a PEG-PLGA nanoparticle and its solubulization of the anticancer peptide, EEK, with good agreement with previously reported experimental structural data. We applied unsupervised machine learning techniques to quantify the conformations that polymers adopt at various locations within the nanoparticle. We find that the local microenvironments formed by the various polymer conformations promote preferential EEK solubilization within specific regions of the NP. This demonstrates that these microenvironments are key in controlling drug storage locations within nanoparticles, supporting the rational design of nanoparticles for therapeutic applications.

Compartmentalized drug localization studies in extracellular vesicles for anticancer therapy

In the development of therapeutic extracellular vesicles (EVs), drug encapsulation efficiencies are significantly lower when compared with synthetic nanomedicines. This is due to the hierarchical structure of the EV membrane and the physicochemical properties of the candidate drug (molecular weight, hydrophilicity, lipophilicity, and so on). As a proof of concept, here we demonstrated the importance of drug compartmentalization in EVs as an additional parameter affecting the therapeutic potential of drug-loaded EVs. In human adipose mesenchymal stem cell (hADSC) derived EVs, we performed a comparative drug loading analysis using two formulations of the same chemotherapeutic molecule - free doxorubicin (DOX) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) lipid-conjugated doxorubicin (L-DOX) - to enhance the intracellular uptake and therapeutic efficacy. By nano surface energy transfer (NSET) and molecular simulation techniques, along with cryo-TEM analysis, we confirmed the differential compartmentalization of these two molecules in hADSC EVs. L-DOX was preferentially adsorbed onto the surface of the EV, due to its higher lipophilicity, whereas free DOX was mostly encapsulated within the EV core. Also, the L-DOX loaded EV (LDOX@EV) returned an almost three-fold higher DOX content as compared to the free DOX loaded EV (DOX@EV), for a given input mass of drug. Based on the cellular investigations, L-DOX@EV showed higher cell internalization than DOX@EV. Also, in comparison with free L-DOX, the magnitude of therapeutic potential enhancement displayed by the surface compartmentalized L-DOX@EV is highly promising and can be exploited to overcome the sensitivity of many potential drugs, which are impermeable in nature. Overall, this study illustrates the significance of drug compartmentalization in EVs and how this could affect intracellular delivery, loading efficiency, and therapeutic effect. This will further lay the foundation for the future systematic investigation of EV-based biotherapeutic delivery platforms for personalized medicine.

Bioactive Suture with Added Innate Defense Functionality for the Reduction of Bacterial Infection and Inflammation

Surgical site infections (SSI) are a clinical and economic burden. Suture-associated SSI may develop when bacteria colonize the suture surface and form biofilms that are resistant to antibiotics. Thrombin-derived C-terminal peptide (TCP)-25 is a host defense peptide with a unique dual mode of action that can target both bacteria and the excessive inflammation induced by bacterial products. The peptide demonstrates therapeutic potential in preclinical in vivo wound infection models. In this study, the authors set out to explore whether TCP-25 can provide a new bioactive innate immune feature to hydrophilic polyglactin sutures (Vicryl). Using a combination of biochemical, biophysical, antibacterial, biofilm, and anti-inflammatory assays in vitro, in silico molecular modeling studies, along with experimental infection and inflammation models in mice, a proof-of-concept that TCP-25 can provide Vicryl sutures with a previously undisclosed host defense capacity, that enables targeting of bacteria, biofilms, and the accompanying inflammatory response, is shown.