Supramolecular Exchange among Assemblies of Opposite Charge Leads to Hierarchical Structures.

Hierarchical assemblies of proteins into fibrillar structures occur in both physiologic and pathologic extracellular spaces and often involve interactions between oppositely charged peptide domains. However, the interplay between tertiary structure dynamics and quaternary hierarchical structure formation remains unclear. In this work, we investigate supramolecular mimics of these systems by mixing one-dimensional assemblies of small alkylated peptides bearing opposite charge and varying in peptide sequence. We found that assemblies with weak cohesive interactions readily create fibrous superstructures of bundled filaments as molecules redistribute upon mixing. Low cohesion allows molecules to escape from the original assemblies and exchange dynamics help them reassemble into electrostatically stable bundles. However, we also found that kinetic barriers can be encountered in these systems and limit formation of the hierarchical structures at pH values where charge densities are high. Increasing intermolecular cohesion using longer peptide sequences that form stable ß-sheets was found to suppress superstructure formation. Our findings suggest that low internal cohesion in protein systems could facilitate the conformational rearrangements required to create hierarchical structures.

Supramolecular Assembly of High-Density Lipoprotein Mimetic Nanoparticles Using Lipid-Conjugated Core Scaffolds.

Synthetic high-density lipoprotein (HDL) mimics have emerged as promising therapeutic agents. However, approaches to date have been unable to reproduce key features of spherical HDLs, which are the most abundant human HDL species. Here, we report the synthesis and characterization of spherical HDL mimics using lipid-conjugated organic core scaffolds. The core design motif constrains and orients phospholipid geometry to facilitate the assembly of soft-core nanoparticles that are approximately 10 nm in diameter and resemble human HDLs in their size, shape, surface chemistry, composition, and protein secondary structure. These particles execute salient HDL functions, including efflux of cholesterol from macrophages, cholesterol delivery to hepatocytes, support lecithin:cholesterol acyltransferase activity, and suppress inflammation. These results represent a significant step toward a genuine functional mimic of human HDLs.

Highly sensitive and ultra-rapid antigen-based detection of SARS-CoV-2 using nanomechanical sensor platform.

The rapid spread of COVID-19 including recent emergence of new variants with its extreme range of pathologies create an urgent need to develop a versatile sensor for a rapid, precise, and highly sensitive detection of SARS-CoV-2. Herein, we report a microcantilever-based optical detection of SARS-CoV-2 antigenic proteins in just few minutes with high specificity by employing fluidic-atomic force microscopy (f-AFM) mediated nanomechanical deflection method. The corresponding antibodies against the target antigens were first grafted on the gold-coated microcantilever surface pre-functionalized with EDC-NHS chemistry for a suitable antibody-antigen interaction. Rapid detection of SARS-CoV-2 nucleocapsid (N) and spike (S1) receptor binding domain (RBD) proteins was first demonstrated at a clinically relevant concentration down to 1 ng/mL (33 pM) by real-time monitoring of nanomechanical signal induced by antibody-antigen interaction. More importantly, we further show high specific detection of antigens with nasopharyngeal swab specimens from patients pre-determined with qRT-PCR. The results take less than 5 min (swab to signal ≤5 min) and exhibit high selectivity and analytical sensitivity (LoD: 100 copies/ ml; 0.71 ng/ml of N protein). These findings demonstrate potential for nanomechanical signal transduction towards rapid antigen detection for early screening of SARS-CoV-2 and its related mutants.

Synthetic high-density lipoprotein nanoparticles: Good things in small packages.

Medicine has been a great beneficiary of the nanotechnology revolution. Nanotechnology involves the synthesis of functional materials with at least one size dimension between 1 and 100 nm. Advances in the field have enabled the synthesis of bio-nanoparticles that can interface with physiological systems to modulate fundamental cellular processes. One example of a diverse acting nanoparticle-based therapeutic is synthetic high-density lipoprotein (HDL) nanoparticles (NP), which have great potential for treating diseases of the ocular surface. Our group has developed a spherical HDL NP using a gold nanoparticle core. HDL NPs: (i) closely mimic the physical and chemical features of natural HDLs; (ii) contain apoA-I; (iii) bind with high-affinity to SR-B1, which is the major receptor through which HDL modulates cell cholesterol metabolism and controls the selective uptake of HDL cargo into cells; (iv) are non-toxic to cells and tissues; and (v) can be chemically engineered to display nearly any surface or core composition desired. With respect to the ocular surface, topical application of HDL NPs accelerates re-epithelization of the cornea following wounding, attenuates inflammation resulting from chemical burns and/or other stresses, and effectively delivers microRNAs with biological activity to corneal cells and tissues. HDL NPs will be the foundation of a new class of topical eye drops with great translational potential and exemplify the impact that nanoparticles can have in medicine.

Prostate cancer extracellular vesicles mediate intercellular communication with bone marrow cells and promote metastasis in a cholesterol-dependent manner.

Primary tumours can establish long-range communication with distant organs to transform them into fertile soil for circulating tumour cells to implant and proliferate, a process called pre-metastatic niche (PMN) formation. Tumour-derived extracellular vesicles (EV) are potent mediators of PMN formation due to their diverse complement of pro-malignant molecular cargo and their propensity to target specific cell types (Costa-Silva et al., 2015; Hoshino et al., 2015; Peinado et al., 2012; Peinado et al., 2017). While significant progress has been made to understand the mechanisms by which pro-metastatic EVs create tumour-favouring microenvironments at pre-metastatic organ sites, comparatively little attention has been paid to the factors intrinsic to recipient cells that may modify the extent to which pro-metastatic EV signalling is received and transduced. Here, we investigated the role of recipient cell cholesterol homeostasis in prostate cancer (PCa) EV-mediated signalling and metastasis. Using a bone metastatic model of enzalutamide-resistant PCa, we first characterized an axis of EV-mediated communication between PCa cells and bone marrow that is marked by in vitro and in vivo PCa EV uptake by bone marrow myeloid cells, activation of NF-κB signalling, enhanced osteoclast differentiation, and reduced myeloid thrombospondin-1 expression. We then employed a targeted, biomimetic approach to reduce myeloid cell cholesterol in vitro and in vivo prior to conditioning with PCa EVs. Reducing myeloid cell cholesterol prevented the uptake of PCa EVs by recipient myeloid cells, abolished NF-κB activity and osteoclast differentiation, stabilized thrombospondin-1 expression, and reduced metastatic burden by 77%. These results demonstrate that cholesterol homeostasis in bone marrow myeloid cells regulates pro-metastatic EV signalling and metastasis by acting as a gatekeeper for EV signal transduction.

An update on synthetic high-density lipoprotein-like nanoparticles for cancer therapy.

Introduction: Significant clinical correlations have been observed between serum high-density lipoprotein (HDL) cholesterol and cancer risk, outcomes, and patient response to specific treatments. While the biological processes underlying these correlations remain unclear, evidence suggests that HDLs actively inhibit tumor progression through a variety of mechanisms. As a result, synthetic HDLs have emerged as attractive agents for targeted cancer therapy. Areas covered: We present a focused review of recent developments in the use of synthetic HDLs for cancer therapy, including roles in drug delivery, RNAi, monotherapy, and immunotherapy. In addition to historic references relevant to the field, we searched the following databases for recent articles published from January 1st, 2015 - May 1st, 2019: MEDLINE, Web of Science Core Collection, and Google Scholar. Expert opinion: Synthetic HDLs have already been used in human patients for cardiovascular disease, and have proven to be effective anticancer agents in pre-clinical testing, which should pave the way for future clinical trials in the setting of cancer. Given the growing notoriety of dysregulated cholesterol homeostasis as a key mechanism of cancer progression, and the immense success of synthetic HDLs in animal models, synthetic HDLs are well-poised to make significant strides toward the clinic as cancer therapy.