Combination of Roll Grinding and High-Pressure Homogenization Can Prepare Stable Bicelles for Drug Delivery

Efficient Drug Loading Method for Poorly Water-Soluble Drug into Bicelles through Passive Diffusion

The bicelle, a type of solid lipid nanoparticle, comprises phospholipids with varying alkyl chain lengths and possesses the ability to solubilize poorly water-soluble drugs. Bicelle preparation is complicated and time-consuming because conventional drug-loading methods in bicelles require multiple rounds of thermal cycling or co-grinding with drugs and lipids. In this study, we proposed a simple drug-loading method for bicelles that utilizes passive diffusion. Drug-unloaded bicelles were placed inside a dialysis device and incubated in a saturated solution of ketoconazole (KTZ), which is a model drug. KTZ was successfully loaded into bare bicelles over time with morphological changes, and the final encapsulated concentration was dependent on the lipid concentration of the bicelles. When polyethylene glycol (PEG) chains of two different lengths (PEG2K and 5K) were incorporated into bicelles, PEG2k and PEG5k bicelles mitigated the morphological changes and improved the encapsulation rate. This mitigation of morphological changes enhanced the encapsulated drug concentration. Specifically, PEG5k bicelles, which exhibited the greatest prevention of morphological changes, had a lower encapsulated concentration after 24 h than that of PEG2k bicelles, indicating that PEGylation with a longer PEG chain length improved the loading capacity but decreased the encapsulation rate owing to the presence of a hydration layer of PEG. Thus, PEG with a certain length is more suitable for passive loading. Moreover, loading factors, such as temperature and vehicles used in the encapsulation process, affected the encapsulation rate of the drug. Taken together, the passive loading method offers high throughput with minimal resources, making it a potentially valuable approach during early drug development phases.

Morphological control and modern applications of bicelles

Bicellar systems have become popularized as their rich morphology can be applied in biochemistry, physical chemistry, and drug delivery technology. To the biochemical field, bicelles are powerful model membranes for the study of transmembrane protein behavior, membrane transport, and environmental interactions with the cell. Their morphological responses to environmental changes reveal a profound fundamental understanding of physical chemistry related to the principle of self-assembly. Recently, they have also drawn significant attention as theranostic nanocarriers in biopharmaceutical and diagnostic research due to their superior cellular uptake compared to liposomes. It is evident that applications are becoming broader, demanding to understand how the bicelle will form and behave in various environments. To consolidate current works on the bicelle's modern applications, this review will discuss various effects of composition and environmental conditions on the morphology, phase behavior, and stability. Furthermore, various applications such as payload entrapment and polymerization templating are presented to demonstrate their versatility and chemical nature.

Molecular-Level Structural Analysis of siRNA-Loaded Lipid Nanoparticles by 1H NMR Relaxometry: Impact of Lipid Composition on Their Structural Properties

1H NMR relaxometry was applied for molecular-level structural analysis of siRNA-loaded lipid nanoparticles (LNPs) to clarify the impact of the neutral lipids, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol, on the physicochemical properties of LNP. Incorporating DSPC and cholesterol in ionizable lipid-based LNP decreased the molecular mobility of ionizable lipids. DSPC reduced the overall molecular mobility of ionizable lipids, while cholesterol specifically decreased the mobility of the hydrophobic tails of ionizable lipids, suggesting that cholesterol filled the gap between the hydrophobic tails of ionizable lipids. The decrease in molecular mobility and change in orientation of lipid mixtures contributed to the maintenance of the stacked bilayer structure of siRNA and ionizable lipids, thereby increasing the siRNA encapsulation efficiency. Furthermore, NMR relaxometry revealed that incorporating those neutral lipids enhanced PEG chain flexibility at the LNP interface. Notably, a small amount of DSPC effectively increased PEG chain flexibility, possibly contributing to the improved dispersion stability and narrower size distribution of LNPs. However, cryogenic transmission electron microscopy represented that adding excess amounts of DSPC and cholesterol into LNP resulted in the formation of deformed particles and demixing cholesterol within the LNP, respectively. The optimal lipid composition of ionizable lipid-based LNPs in terms of siRNA encapsulation efficiency and PEG chain flexibility was rationalized based on the molecular-level characterization of LNPs. Moreover, the NMR relaxation rate of tertiary amine protons of ionizable lipids, which are the interaction site with siRNA, can be a valuable indicator of the encapsulated amount of siRNA within LNPs. Thus, NMR-based analysis can be a powerful tool for efficiently designing LNP formulations and their quality control based on the molecular-level elucidation of the physicochemical properties of LNPs.

One-Step Pharmaceutical Preparation of PEG-Modified Exosomes Encapsulating Anti-Cancer Drugs by a High-Pressure Homogenization Technique

The use of exosomes encapsulating therapeutic agents for the treatment of diseases is of increasing interest. However, some concerns such as limited efficiency and scalability of conventional drug encapsulation methods to exosomes have still remained; thus, a new approach that enables encapsulation of therapeutic agents with superior efficiency and scalability is required. Herein, we used RAW264 macrophage cell-derived exosomes (RAW-Exos) and demonstrated that high-pressure homogenization (HPH) using a microfluidizer decreased their particle size without changing their morphology, the amount of exosomal marker proteins, and cellular uptake efficiency into RAW264 and colon-26 cancer cells. Moreover, HPH allowed for modification of polyethylene glycol (PEG)-conjugated lipids onto RAW-Exos, as well as encapsulation of the anti-cancer agent doxorubicin. Importantly, the doxorubicin encapsulation efficiency became higher upon increasing the process pressure and simultaneous HPH with PEG-lipids. Moreover, treatment with PEG-modified RAW-Exos encapsulating doxorubicin significantly suppressed tumor growth in colon-26-bearing mice. Taken together, these results suggest that HPH using a microfluidizer could be useful to prepare PEG-modified Exos encapsulating anti-cancer drugs via a one-step pharmaceutical process, and that the prepared functional Exos could be applied for the treatment of cancer in vivo.

Scrutinizing the Feasibility of Nonionic Surfactants to Form Isotropic Bicelles of Curcumin: a Potential Antiviral Candidate Against COVID-19

Investigating bicelles as an oral drug delivery system and exploiting their structural benefits can pave the way to formulate hydrophobic drugs and potentiate their activity. Herein, the ability of non-ionic surfactants (labrasol®, tween 80, cremophore EL and pluronic F127) to form curcumin loaded bicelles with phosphatidylcholine, utilizing a simple method, was investigated. Molecular docking was used to understand the mechanism of bicelles formation. The % transmittance and TEM exhibited bicelles formation with labrasol® and tween 80, while cremophor EL and pluronic F127 tended to form mixed micelles. The surfactant-based nanostructures significantly improved curcumin dissolution (99.2 ± 2.6% within 10 min in case of tween 80-based bicelles) compared to liposomes and curcumin suspension in non-sink conditions. The prepared formulations improved curcumin ex vivo permeation over liposomes and drug suspension. Further, the therapeutic antiviral activity of the formulated curcumin against SARS-CoV-2 was potentiated over drug suspension. Although both Labrasol® and tween 80 bicelles could form bicelles and enhance the oral delivery of curcumin when compared to liposomes and drug suspension, the mixed micelles formulations depicted superiority than bicelles formulations. Our findings provide promising formulations that can be utilized for further preclinical and clinical studies of curcumin as an antiviral therapy for COVID-19 patients. Graphical Abstract.

Recent Advancements in Liposome-Targeting Strategies for the Treatment of Gliomas: A Systematic Review

Malignant tumors represent some of the most intractable diseases that endanger human health. A glioma is a tumor of the central nervous system that is characterized by severe invasiveness, blurred boundaries between the tumor and surrounding normal tissue, difficult surgical removal, and high recurrence. Moreover, the blood-brain barrier (BBB) and multidrug resistance (MDR) are important factors that contribute to the lack of efficacy of chemotherapy in treating gliomas. A liposome is a biofilm-like drug delivery system with a unique phospholipid bilayer that exhibits high affinities with human tissues/organs (e.g., BBB). After more than five decades of development, classical and engineered liposomes consist of four distinct generations, each with different characteristics: (i) traditional liposomes, (ii) stealth liposomes, (iii) targeting liposomes, and (iv) biomimetic liposomes, which offer a promising approach to promote drugs across the BBB and to reverse MDR. Here, we review the history, preparatory methods, and physicochemical properties of liposomes. Furthermore, we discuss the mechanisms by which liposomes have assisted in the diagnosis and treatment of gliomas, including drug transport across the BBB, inhibition of efflux transporters, reversal of MDR, and induction of immune responses. Finally, we highlight ongoing and future clinical trials and applications toward further developing and testing the efficacies of liposomes in treating gliomas.

A Liposomal Formulation for Improving Solubility and Oral Bioavailability of Nifedipine

Proliposomes were used to improve the solubility and oral bioavailability of nifedipine. Nifedipine proliposomes were prepared by methanol injection-spray drying method. The response surface method was used to optimize formulation to enhance the encapsulation efficiency (EE%) of nifedipine. The particle size of nifedipine proliposomes after rehydration was 114 nm. Surface morphology of nifedipine proliposomes was observed by a scanning electron microscope (SEM) and interaction of formulation ingredients was assessed by differential scanning calorimetry (DSC). The solubility of nifedipine is improved 24.8 times after forming proliposomes. In vitro release experiment, nifedipine proliposomes had a control release effect, especially in simulated gastric fluid. In vivo, nifedipine proliposomes significantly improved the bioavailability of nifedipine. The area under the concentration-time curve (AUC_0–∞) of nifedipine proliposomes was about 10 times than nifedipine after oral administration. The elimination half-life (T_1/2β) of nifedipine was increased from 1.6 h to 6.6 h. In conclusion, proliposomes was a promising system to deliver nifedipine through oral route and warranted further investigation.