Development of Nanoscale Oil Bodies for Targeted Treatment of Lung Cancer

Methods for making and observing model lipid droplets

We present methods for making and testing the membrane biophysics of model lipid droplets (LDs). Methods are described for imaging LDs ranging in size from 0.1 to 40 μm in diameter with high-resolution microscopy and spectroscopy. With known LD compositions, membrane binding, sorting, diffusion, and tension were measured via fluorescence correlation spectroscopy (FCS), fluorescence recovery after photobleaching (FRAP), fluorescence lifetime imaging microscopy (FLIM), atomic force microscopy (AFM), and imaging flow cytometry. Additionally, a custom, small-volume pendant droplet tensiometer is described and used to measure the association of phospholipids to the LD surface. These complementary, cross-validating methods of measuring LD membrane behavior reveal the interplay of biophysical processes on lipid droplet monolayers.

Artificial oil bodies: A review on composition, properties, biotechnological applications, and improvement methods

In order to simulate the structure of natural oil body, artificial oil bodies (AOBs) are fabricated by the integration of oleosins, triacylglycerols (TAGs) and phospholipids (PLs) in vitro. Recently, AOBs have gained great research interest both in the food and biological fields due to its ability to act as a novel delivery system for bioactive compounds and as a carrier for target proteins. This review aims to summarize the composition and the preparation methods of AOBs, examine the factors influencing their stability. Moreover, this contribution focusses on exploring the application of AOBs to encapsulate functional ingredients that are prone to oxidation as well as improve efficiency involved in protein purification, renaturation and immobilization by reducing the complex steps. In addition, the improvement measures to further enhance the stability and efficacy of AOBs are also discussed. The application of AOBs is expected to be a big step towards replacing existing bioreactors and delivery systems.

Methods for making and observing model lipid droplets

The mechanisms by which the lipid droplet (LD) membrane is remodeled in concert with the activation of lipolysis incorporate a complex interplay of proteins, phospholipids, and neutral lipids. Model LDs (mLDs) provide an isolated, purified system for testing the mechanisms by which the droplet composition, size, shape, and tension affects triglyceride metabolism. Described here are methods of making and testing mLDs ranging from 0.1 to 40 μm diameter with known composition. Methods are described for imaging mLDs with high-resolution microscopy during buffer exchanges for the measurement of membrane binding, diffusion, and tension via fluorescence correlation spectroscopy (FCS), fluorescence recovery after photobleaching (FRAP), fluorescence lifetime imaging microscopy (FLIM), atomic force microscopy (AFM), pendant droplet tensiometry, and imaging flow cytometry. These complementary, cross-validating methods of measuring LD membrane behavior reveal the interplay of biophysical processes in triglyceride metabolism.

Mammalian lipid droplets: structural, pathological, immunological and anti-toxicological roles

Mammalian lipid droplets (LDs) are specialized cytosolic organelles consisting of a neutral lipid core surrounded by a membrane made up of a phospholipid monolayer and a specific population of proteins that varies according to the location and function of each LD. Over the past decade, there have been significant advances in the understanding of LD biogenesis and functions. LDs are now recognized as dynamic organelles that participate in many aspects of cellular homeostasis plus other vital functions. LD biogenesis is a complex, highly-regulated process with assembly occurring on the endoplasmic reticulum although aspects of the underpinning molecular mechanisms remain elusive. For example, it is unclear how many enzymes participate in the biosynthesis of the neutral lipid components of LDs and how this process is coordinated in response to different metabolic cues to promote or suppress LD formation and turnover. In addition to enzymes involved in the biosynthesis of neutral lipids, various scaffolding proteins play roles in coordinating LD formation. Despite their lack of ultrastructural diversity, LDs in different mammalian cell types are involved in a wide range of biological functions. These include roles in membrane homeostasis, regulation of hypoxia, neoplastic inflammatory responses, cellular oxidative status, lipid peroxidation, and protection against potentially toxic intracellular fatty acids and lipophilic xenobiotics. Herein, the roles of mammalian LDs and their associated proteins are reviewed with a particular focus on their roles in pathological, immunological and anti-toxicological processes.

How plants solubilise seed fats: revisiting oleosin structure and function to inform commercial applications

Plants store triacylglycerides in organelles called oil bodies, which are important fuel sources for germination. Oil bodies consist of a lipid core surrounded by an interfacial single layer membrane of phospholipids and proteins. Oleosins are highly conserved plant proteins that are important for oil body formation, solubilising the triacylglycerides, stabilising oil bodies, and playing a role in mobilising the fuel during the germination process. The domain structure of oleosins is well established, with N- and C-terminal domains that are hydrophilic flanking a long hydrophobic domain that is proposed to protrude into the triacylglyceride core of the oil body. However, beyond this general understanding, little molecular level detail on the structure is available and what is known is disputed. This lack of knowledge limits our understanding of oleosin function and concomitantly our ability to engineer them. Here, we review the state of play in the literature regarding oleosin structure and function, and provide some examples of how oleosins can be used in commercial settings.

Fabrication and characterization of β-carotene emulsions stabilized by soy oleosin and lecithin mixtures with a composition mimicking natural soy oleosomes

Natural soy oleosomes are known to have a remarkable stability, given the advantage of their sophisticated membrane. The aim of the present study is to examine the concept of fabricating a β-carotene emulsion stabilized by soy oleosin (OLE) and lecithin (LEC) mixtures mimicking the membrane composition of soy oleosomes while providing preferable stability and bioaccessibility. For this, the fabricated emulsion was characterized in terms of droplet size distribution, and emulsion structure, stability and digestion (release and absorption of lipophilic β-carotene). Compared to SPI/LEC (10 : 1) stabilized emulsions, the OLE/LEC (10 : 1) mixture stabilized emulsion exhibited the highest emulsifying activity index (EAI) and emulsifying stability index (ESI) values, and higher encapsulation efficiency. Results show that the β-carotene emulsion stabilized by OLE and LEC mixtures at the ratio of 10 : 1 (w/w) has the most uniform droplet distribution and highest stability. The in vitro gastrointestinal digestion test revealed that the β-carotene emulsion stabilized by OLE and LEC mixtures was digested more rapidly than the emulsion stabilized by soy protein isolate (SPI) and LEC mixtures. In turn, the bioaccessibility and cellular uptake of β-carotene were enhanced, resulting in a higher absorption, a desirable feature of nutrition delivery systems. Our results demonstrated a promising way to fabricate emulsions mimicking natural soy oleosomes.

Biophysical characterization of full-length oleosin in dodecylphosphocholine micelles

Oleosin is a hydrophobic protein that punctuates the surface of plant seed lipid droplets, which are 20 nm-100 μm entities that serve as reservoirs for high-energy metabolites. Oleosin is purported to stabilize lipid droplets, but its exact mechanism of stabilization has not been established. Probing the structure of oleosin directly in lipid droplets is challenging due to the size of lipid droplets and their high degree of light scattering. Therefore, a medium in which the native structure of oleosin is retained, but is also amenable to spectroscopic studies is needed. Here, we show, using a suite of biophysical techniques, that dodecylphosphocholine micelles appear to support the tertiary structure of the oleosin protein (i.e., hairpin conformation) and render the protein in an oligomeric state that is amenable to more sophisticated biophysical techniques such as NMR.

In situ delivery of biobutyrate by probiotic Escherichia coli for cancer therapy

Butyrate has a bioactive function to reduce carcinogenesis. To achieve targeted cancer therapy, this study developed bacterial cancer therapy (BCT) with butyrate as a payload. By metabolic engineering, Escherichia coli Nissle 1917 (EcN) was reprogrammed to synthesize butyrate (referred to as biobutyrate) and designated EcN-BUT. The adopted strategy includes construction of a synthetic pathway for biobutyrate and the rational design of central metabolism to increase the production of biobutyrate at the expense of acetate. With glucose, EcN-BUT produced primarily biobutyrate under the hypoxic condition. Furthermore, human colorectal cancer cell was administrated with the produced biobutyrate. It caused the cell cycle arrest at the G1 phase and induced the mitochondrial apoptosis pathway independent of p53. In the tumor-bearing mice, the injected EcN-BUT exhibited tumor-specific colonization and significantly reduced the tumor volume by 70%. Overall, this study opens a new avenue for BCT based on biobutyrate.

Preparation and characterization of neutrally-buoyant oleosin-rich synthetic lipid droplets

Lipid droplets also known as oil bodies are found in a variety of organisms and function as stores of high-energy metabolites. Recently, there has been interest in using lipid droplets for protein production and drug delivery. Artificial lipid droplets have been previously prepared, but their short lifetime in solution and inhomogeneity has severely limited their applicability. Herein we report an improved methodology for the production of synthetic lipid droplets that overcomes the aforementioned limitations. These advancements include: 1) development of a methodology for the expression and purification of high-levels of oleosin, a crucial lipid droplet component, 2) preparation of neutrally-buoyant synthetic lipid droplets, and 3) production of synthetic lipid droplets of a specific size. Together, these important enhancements will facilitate the advancement of lipid droplet science and its application in biotechnology.

Metabolic engineering of probiotic Escherichia coli for cytolytic therapy of tumors

Bacterial cancer therapy was developed using probiotic Escherichia coli Nissle 1917 (EcN) for medical intervention of colorectal cancer. EcN was armed with HlyE, a small cytotoxic protein, under the control of the araBAD promoter (PBAD). The intrinsic limitation of PBAD for the gene expression is known to be negated by glucose and afflicted with all-or-nothing induction in host bacteria. This issue was addressed by metabolic engineering of EcN to uncouple the glucose-mediated control circuit and the L-arabinose transport-induction loop and to block L-arabinose catabolism. As a result, the reprogrammed strain (designated EcNe) enabled efficient expression of HlyE in a temporal control manner. The HlyE production was insensitive to glucose and reached a saturated level in response to L-arabinose at 30-50 μM. Moreover, the administrated EcNe exhibited tumor-specific colonization with the tumor-to-organ ratio of 106:1. Equipped with HlyE, EcNe significantly caused tumor regression in mice xenografted with human colorectal cancer cells. Overall, this study proposes a new strategy for the bacteria-mediated delivery of therapeutic proteins to tumors.

Nutraceutical Vegetable Oil Nanoformulations for Prevention and Management of Diseases

The scientific community is becoming increasingly interested in identifying, characterizing, and delivering nutraceuticals, which constitutes a multi-billion-dollar business. These bioactive agents are claimed to exhibit several health benefits, including the prevention and treatment of diseases such as arthritis, cancer, osteoporosis, cataracts, Alzheimer's, and Huntington's diseases, heart, brain and metabolic disorders, etc. Nutraceuticals are typically consumed as part of a regular human diet and are usually present within foods, comprising vegetable oil, although at low levels and variable composition. Thus, it is difficult to control the type, amount and frequency of their ingestion by individuals. Nanoformulations about vegetable oil-based bioactive compounds with nutraceutical properties are useful for overcoming these issues, while improving the uptake, absorption, and bioavailability in the body. The purpose of this current study is to review papers on such nanoformulations, particularly those relevant for health benefits and the prevention and management of diseases, as well as bioactives extracted from vegetable oils enhancing the drug effectiveness, retrieved through bibliographic databases by setting a timespan from January 2000 to April 2020 (about 1758 records).