Therapeutic nanoparticles (TNPs) aim to deliver drugs more safely and effectively to cancers, yet clinical results have been unpredictable owing to limited in vivo understanding. Here we use single-cell imaging of intratumoral TNP pharmacokinetics and pharmacodynamics to better comprehend their heterogeneous behavior. Model TNPs comprised of a fluorescent platinum(IV) pro-drug and a clinically-tested polymer platform (PLGA-b-PEG) promote long drug circulation and alter accumulation by directing cellular uptake toward tumor associated macrophages (TAMs). Simultaneous imaging of TNP vehicle, its drug payload, and single-cell DNA damage response reveals that TAMs serve as a local drug depot that accumulates significant vehicle from which DNA damaging Pt payload gradually releases to neighboring tumor cells. Correspondingly, TAM depletion reduces intratumoral TNP accumulation and efficacy. Thus, nanotherapeutics co-opt TAMs for drug delivery, which has implications for TNP design and for selecting patients into trials.

PTEN is a well-characterized tumour-suppressor gene that is lost or mutated in about half of metastatic castration-resistant prostate cancers and in many other human cancers. The restoration of functional PTEN as a treatment for prostate cancer has however proven difficult. Here, we show that PTEN mRNA can be reintroduced into PTEN-null prostate cancer cells in vitro and in vivo via its encapsulation in polymer-lipid hybrid nanoparticles coated with a poly(ethylene glycol) shell. The nanoparticles are stable in serum, elicit low toxicity, enable high PTEN mRNA transfection in prostate cancer cells, and lead to significant inhibition of tumour growth when delivered systemically in multiple mouse models of prostate cancer. We also show that the restoration of PTEN function in PTEN-null prostate cancer cells inhibits the PI3K-AKT pathway and enhances apoptosis. Our findings provide proof-of-principle evidence of the restoration of mRNA-based tumour suppression in vivo .

Upon entering the physiological environment, nanoparticles (NPs) are immediately surrounded by a complex and tightly bound layer of biomolecules, or '(hard) protein corona'. The corona controls NP fate in vivo and becomes the interface with cells. One of nanomedicine's central goals is to make NPs capable of active targeting in both imaging and therapy. If the NP is not designed correctly, the resulting corona can cause mistargeting and aberrant biodistribution, unanticipated toxicity, and low therapeutic efficacy. Here we present groundbreaking concepts about nanobio interactions and discuss approaches to bypass protein corona issues and thus enhance the efficacy of NPs.

Complementary coiled coil forming lipidated peptides embedded in liposomal membranes are able to induce rapid, controlled, and targeted membrane fusion. Traditionally, such fusogenic liposomes are prepared by mixing lipids and lipidated peptides in organic solvent (e.g., chloroform). Here we prepared fusogenic liposomes in situ, i.e., by addition of a lipidated peptide solution to plain liposomes. As the lipid anchor is vital for the correct insertion of lipidated peptides into liposomal membranes, a small library of lipidated coiled coil forming peptides was designed in which the lipid structure was varied. The fusogenicity was screened using lipid and content mixing assays showing that cholesterol modified coiled coil peptides induced the most efficient fusion of membranes. Importantly, both lipid and content mixing experiments demonstrated that the in situ modification of plain liposomes with the cholesterol modified peptides yielded highly fusogenic liposomes. This work shows that existing membranes can be activated with lipidated coiled coil forming peptides, which might lead to highly potent applications such as the fusion of liposomes with cells.

Messenger RNA (mRNA) has recently emerged with remarkable potential as an effective alternative to DNA-based therapies because of several unique advantages. mRNA does not require nuclear entry for transfection activity and has a negligible chance of integrating into the host genome which excludes the possibility of potentially detrimental genomic alternations. Chemical modification of mRNA has further enhanced its stability and decreased its activation of innate immune responses. Additionally, mRNA has been found to have rapid expression and predictable kinetics. Nevertheless, the ubiquitous application of mRNA remains challenging given its unfavorable attributes, such as large size, negative charge and susceptibility to enzymatic degradation. Further refinement of mRNA delivery modalities is therefore essential for its development as a therapeutic tool. This review provides an exclusive overview of current state-of-the-art biomaterials and nanotechnology platforms for mRNA delivery, and discusses future prospects to bring these exciting technologies into clinical practice.

With the capability of specific silencing of target gene expression, RNA interference (RNAi) technology is emerging as a promising therapeutic modality for the treatment of cancer and other diseases. One key challenge for the clinical applications of RNAi is the safe and effective delivery of RNAi agents such as small interfering RNA (siRNA) to a particular nonliver diseased tissue (e.g., tumor) and cell type with sufficient cytosolic transport. In this work, we proposed a multifunctional envelope-type nanoparticle (NP) platform for prostate cancer (PCa)-specific in vivo siRNA delivery. A library of oligoarginine-functionalized and sharp pH-responsive polymers was synthesized and used for self-assembly with siRNA into NPs with the features of long blood circulation and pH-triggered oligoarginine-mediated endosomal membrane penetration. By further modification with ACUPA, a small molecular ligand specifically recognizing prostate-specific membrane antigen (PSMA) receptor, this envelope-type nanoplatform with multifunctional properties can efficiently target PSMA-expressing PCa cells and silence target gene expression. Systemic delivery of the siRNA NPs can efficiently silence the expression of prohibitin 1 (PHB1), which is upregulated in PCa and other cancers, and significantly inhibit PCa tumor growth. These results suggest that this multifunctional envelope-type nanoplatform could become an effective tool for PCa-specific therapy.

Fusion of lipid membranes is an important natural process for the intra- and intercellular exchange of molecules. However, little is known about the actual fusion mechanism at the molecular level. In this study we examine a system that models the key features of this process. For the molecular recognition between opposing membranes two membrane anchored heterodimer coiled-coil forming peptides called 'E' (EIAALEK)3 and 'K' (KIAALKE)3 were used. Lipid monolayers and IR reflection absorption spectroscopy (IRRAS) revealed the interactions of the peptides 'E', 'K', and their parallel coiled-coil complex 'E/K' with the phospholipid membranes and thereby mimicked the pre- and postfusion states, respectively. The peptides adopted α-helical structures and were incorporated into the monolayers with parallel orientation. The strength of binding to the monolayer differed for the peptides and tethering them to the membrane increased the interactions even further. Remarkably, these interactions played a role even in the postfusion state. These findings shed light on important mechanistic details of the membrane fusion process in this model system. Furthermore, their implications will help to improve the rational design of new artificial membrane fusion systems, which have a wide range of potential applications in supramolecular chemistry and biomedicine.

Superficial appeal: The surface of live cells and zebrafish embryos can be modified by a supramolecular method. A peptide pair that forms a coiled coil at the cell membrane can be used to dock liposomes in in vitro and in vivo environments (see scheme). This tool can be used in biophysical studies of biological processes occurring at membranes.