A fast and straightforward procedure for vault nanoparticle purification and the characterization of its endocytic uptake

An Efficient Method for Vault Nanoparticle Conjugation with Finely Adjustable Amounts of Antibodies and Small Molecules

Vaults are eukaryotic ribonucleoproteins consisting of 78 copies of the major vault protein (MVP), which assemble into a nanoparticle with an about 60 nm volume-based size, enclosing other proteins and RNAs. Regardless of their physiological role(s), vaults represent ideal, natural hollow nanoparticles, which are produced by the assembly of the sole MVP. Here, we have expressed in Komagataella phaffi and purified an MVP variant carrying a C-terminal Z peptide (vault-Z), which can tightly bind an antibody's Fc portion, in view of targeted delivery. Via surface plasmon resonance analysis, we could determine a 2.5 nM affinity to the monoclonal antibody Trastuzumab (Tz)/vault-Z 1:1 interaction. Then, we characterized the in-solution interaction via co-incubation, ultracentrifugation, and analysis of the pelleted proteins. This showed virtually irreversible binding up to an at least 10:1 Tz/vault-Z ratio. As a proof of concept, we labeled the Fc portion of Tz with a fluorophore and conjugated it with the nanoparticle, along with either Tz or Cetuximab, another monoclonal antibody. Thus, we could demonstrate antibody-dependent, selective uptake by the SKBR3 and MDA-MB 231 breast cancer cell lines. These investigations provide a novel, flexible technological platform that significantly extends vault-Z's applications, in that it can be stably conjugated with finely adjusted amounts of antibodies as well as of other molecules, such as fluorophores, cell-targeting peptides, or drugs, using the Fc portion as a scaffold.

Dihydrocaffeic acid grafted chitosan self-assembled nanomicelles with enhanced intestinal transport and antioxidant properties of chicoric acid

Chicoric acid (CA) plays a crucial role as a functional factor within the realm of foods, showcasing a wide array of bioactivities. Nevertheless, its oral bioavailability is significantly limited. To optimize the intestinal absorption and bolster the antioxidant capacity of CA, a water-soluble dihydrocaffeic acid grafted chitosan copolymer (DA-g-CS) was synthesized using a conventional free radicals system, and subsequently utilized for the encapsulation of CA within self-assembled nanomicelles (DA-g-CS/CA). The average particle size of DA-g-CS/CA was 203.3 nm, while the critical micelle concentration was 3.98 × 10-4 mg/mL. Intestinal transport studies revealed that DA-g-CS/CA penetrated cells via the macropinocytosis pathway, exhibiting the cellular uptake rate 1.64 times higher than that of CA. This substantial enhancement in the intestinal transport of CA underscores the significant improvements achieved through DA-g-CS/CA delivery. The pharmacokinetic results demonstrated that DA-g-CS/CA exhibited a remarkable bioavailability 2.24 times that of CA. Furthermore, the antioxidant assessment demonstrated that DA-g-CS/CA exhibited exceptional antioxidant properties in comparison to CA. It demonstrated enhanced protective and mitigating effects in the H2O2-induced oxidative damage model, while also displaying a stronger emphasis on protective effects rather than attenuating effects. These findings aim to establish a solid theoretical foundation for the advancement of CA in terms of its oral absorption and the development of functional food products.

Addressing Critical Issues Related to Storage and Stability of the Vault Nanoparticle Expressed and Purified from Komagataella phaffi

The vault nanoparticle is a eukaryotic assembly consisting of 78 copies of the 99-kDa major vault protein. They generate two cup-shaped symmetrical halves, which in vivo enclose protein and RNA molecules. Overall, this assembly is mainly involved in pro-survival and cytoprotective functions. It also holds a remarkable biotechnological potential for drug/gene delivery, thanks to its huge internal cavity and the absence of toxicity/immunogenicity. The available purification protocols are complex, partly because they use higher eukaryotes as expression systems. Here, we report a simplified procedure that combines human vault expression in the yeast Komagataella phaffii, as described in a recent report, and a purification process we have developed. This consists of RNase pretreatment followed by size-exclusion chromatography, which is far simpler than any other reported to date. Protein identity and purity was confirmed by SDS-PAGE, Western blot and transmission electron microscopy. We also found that the protein displayed a significant propensity to aggregate. We thus investigated this phenomenon and the related structural changes by Fourier-transform spectroscopy and dynamic light scattering, which led us to determine the most suitable storage conditions. In particular, the addition of either trehalose or Tween-20 ensured the best preservation of the protein in native, soluble form.

Tailored Functionalized Protein Nanocarriers for Cancer Therapy: Recent Developments and Prospects

Recently, the potential use of nanoparticles for the targeted delivery of therapeutic and diagnostic agents has garnered increased interest. Several nanoparticle drug delivery systems have been developed for cancer treatment. Typically, protein-based nanocarriers offer several advantages, including biodegradability and biocompatibility. Using genetic engineering or chemical conjugation approaches, well-known naturally occurring protein nanoparticles can be further prepared, engineered, and functionalized in their self-assembly to meet the demands of clinical production efficiency. Accordingly, promising protein nanoparticles have been developed with outstanding tumor-targeting capabilities, ultimately overcoming multidrug resistance issues, in vivo delivery barriers, and mimicking the tumor microenvironment. Bioinspired by natural nanoparticles, advanced computational techniques have been harnessed for the programmable design of highly homogenous protein nanoparticles, which could open new routes for the rational design of vaccines and drug formulations. The current review aims to present several significant advancements made in protein nanoparticle technology, and their use in cancer therapy. Additionally, tailored construction methods and therapeutic applications of engineered protein-based nanoparticles are discussed.

Escherichia coli as a New Platform for the Fast Production of Vault-like Nanoparticles: An Optimized Protocol

Vaults are protein nanoparticles that are found in almost all eukaryotic cells but are absent in prokaryotic ones. Due to their properties (nanometric size, biodegradability, biocompatibility, and lack of immunogenicity), vaults show enormous potential as a bio-inspired, self-assembled drug-delivery system (DDS). Vault architecture is directed by self-assembly of the "major vault protein" (MVP), the main component of this nanoparticle. Recombinant expression (in different eukaryotic systems) of the MVP resulted in the formation of nanoparticles that were indistinguishable from native vaults. Nowadays, recombinant vaults for different applications are routinely produced in insect cells and purified by successive ultracentrifugations, which are both tedious and time-consuming strategies. To offer cost-efficient and faster protocols for nanoparticle production, we propose the production of vault-like nanoparticles in Escherichia coli cells, which are still one of the most widely used prokaryotic cell factories for recombinant protein production. The strategy proposed allowed for the spontaneous encapsulation of the engineered cargo protein within the self-assembled vault-like nanoparticles by simply mixing the clarified lysates of the producing cells. Combined with well-established affinity chromatography purification methods, our approach contains faster, cost-efficient procedures for biofabrication in a well-known microbial cell factory and the purification of "ready-to-use" loaded protein nanoparticles, thereby opening the way to faster and easier engineering and production of vault-based DDSs.

All-in-one biofabrication and loading of recombinant vaults in human cells

One of the most promising approaches in the drug delivery field is the use of naturally occurring self-assembling protein nanoparticles, such as virus-like particles, bacterial microcompartments or vault ribonucleoprotein particles as drug delivery systems (DDS). Among them, eukaryotic vaults show a promising future due to their structural features, in vitro stability and non-immunogenicity. Recombinant vaults are routinely produced in insect cells and purified through several ultracentrifugations, both tedious and time-consuming processes. As an alternative, this work proposes a new approach and protocols for the production of recombinant vaults in human cells by transient gene expression of a His-tagged version of the Major Vault Protein (MVP-H6), the development of new affinity-based purification processes for such recombinant vaults, and the all-in-one biofabrication and encapsulation of a cargo recombinant protein within such vaults by their co-expression in human cells. Protocols proposed here allow the easy and straightforward biofabrication and purification of engineered vaults loaded with virtually any INT-tagged cargo protein, in very short times, paving the way to faster and easier engineering and production of better and more efficient DDS.

Mechanism of Lentinan Intestinal Absorption: Clathrin-Mediated Endocytosis and Macropinocytosis

Lentinan (LNT), a typical triple helix β-glucan extracted from Lentinus edodes, has been widely used as a functional food and an orally administered drug. However, its oral pharmacokinetics has been rarely reported. The aim of this work is to systematically study the pharmacokinetics and intestinal absorption mechanism of LNT after oral administration. Radioactive 99m-technetium (^99mTc) was introduced to label LNT to determine the plasma concentration, tissue distribution, and excretion of the β-glucan in rats after oral administration. The results confirmed the absorption of LNT, with the maximal plasma concentration reached at 1 h. 5-([4,6-Dichlorotriazin-2-yl]amino)fluorescein (DTAF) was used to label LNT to explore the absorption mechanism of LNT, utilizing both a Ussing chamber and a monolayer of Caco-2 cells. These transport assays showed that LNT could penetrate through the intestine and epithelial monolayer, which was mediated by macropinocytosis and clathrin-mediated endocytosis. These findings provide a pharmacokinetic reference for LNT and help provide a greater understanding of the absorption of β-glucans in general.

The Vault Nanoparticle: A Gigantic Ribonucleoprotein Assembly Involved in Diverse Physiological and Pathological Phenomena and an Ideal Nanovector for Drug Delivery and Therapy

Simple Summary

In recent decades, a molecular complex referred to as vault nanoparticle has attracted much attention by the scientific community, due to its unique properties. At the molecular scale, it is a huge assembly consisting of 78 97-kDa polypeptide chains enclosing an internal cavity, wherein enzymes involved in DNA integrity maintenance and some small noncoding RNAs are accommodated. Basically, two reasons justify this interest. On the one hand, this complex represents an ideal tool for the targeted delivery of drugs, provided it is suitably engineered, either chemically or genetically; on the other hand, it has been shown to be involved in several cellular pathways and mechanisms that most often result in multidrug resistance. It is therefore expected that a better understanding of the physiological roles of this ribonucleoproteic complex may help develop new therapeutic strategies capable of coping with cancer progression. Here, we provide a comprehensive review of the current knowledge.

Abstract

The vault nanoparticle is a eukaryotic ribonucleoprotein complex consisting of 78 individual 97 kDa-“major vault protein” (MVP) molecules that form two symmetrical, cup-shaped, hollow halves. It has a huge size (72.5 × 41 × 41 nm) and an internal cavity, wherein the vault poly(ADP-ribose) polymerase (vPARP), telomerase-associated protein-1 (TEP1), and some small untranslated RNAs are accommodated. Plenty of literature reports on the biological role(s) of this nanocomplex, as well as its involvement in diseases, mostly oncological ones. Nevertheless, much has still to be understood as to how vault participates in normal and pathological mechanisms. In this comprehensive review, current understanding of its biological roles is discussed. By different mechanisms, vault’s individual components are involved in major cellular phenomena, which result in protection against cellular stresses, such as DNA-damaging agents, irradiation, hypoxia, hyperosmotic, and oxidative conditions. These diverse cellular functions are accomplished by different mechanisms, mainly gene expression reprogramming, activation of proliferative/prosurvival signaling pathways, export from the nucleus of DNA-damaging drugs, and import of specific proteins. The cellular functions of this nanocomplex may also result in the onset of pathological conditions, mainly (but not exclusively) tumor proliferation and multidrug resistance. The current understanding of its biological roles in physiological and pathological processes should also provide new hints to extend the scope of its exploitation as a nanocarrier for drug delivery.

Latest Advances in the Development of Eukaryotic Vaults as Targeted Drug Delivery Systems

The use of smart drug delivery systems (DDSs) is one of the most promising approaches to overcome some of the drawbacks of drug-based therapies, such as improper biodistribution and lack of specific targeting. Some of the most attractive candidates as DDSs are naturally occurring, self-assembling protein nanoparticles, such as viruses, virus-like particles, ferritin cages, bacterial microcompartments, or eukaryotic vaults. Vaults are large ribonucleoprotein nanoparticles present in almost all eukaryotic cells. Expression in different cell factories of recombinant versions of the "major vault protein" (MVP) results in the production of recombinant vaults indistinguishable from native counterparts. Such recombinant vaults can encapsulate virtually any cargo protein, and they can be specifically targeted by engineering the C-terminus of MVP monomer. These properties, together with nanometric size, a lumen large enough to accommodate cargo molecules, biodegradability, biocompatibility and no immunogenicity, has raised the interest in vaults as smart DDSs. In this work we provide an overview of eukaryotic vaults as a new, self-assembling protein-based DDS, focusing in the latest advances in the production and purification of this platform, its application in nanomedicine, and the current preclinical and clinical assays going on based on this nanovehicle.