Pharmacokinetics of lipid-drug conjugates loaded into liposomes

Rg3-lipo biomimetic delivery of paclitaxel enhances targeting of tumors and myeloid-derived suppressor cells

Liposomal drug delivery systems have revolutionized traditional cytotoxic drugs. However, the relative instability and toxicity of the existing liposomal drug delivery systems compromised their efficacy. Herein, we present Rg3-lipo, an innovative drug delivery system using a glycosyl moiety-enriched ginsenoside (Rg3). This system is distinguished by its glycosyl moieties exposed on the liposomal surface. These moieties imitate human cell membranes to stabilize and evade phagocytic clearance. The Rg3-lipo system loaded with paclitaxel (PTX-Rg3-lipo) demonstrated favorable bioavailability and safety in Sprague-Dawley rats, beagle dogs, and cynomolgus monkeys. With its glycosyl moieties recognizing tumor cells via the glucose transporter Glut1, PTX-Rg3-lipo inhibited gastric, breast, and esophageal cancers in human cancer cell lines, tumor-bearing mice, and patient-derived xenograft models. These glycosyl moieties selectively targeted myeloid-derived suppressor cells (MDSCs) through the glucose transporter Glut3 to attenuate their immunosuppressive effect. The mechanism study revealed that Rg3-lipo suppressed glycolysis and downregulated the transcription factors c-Maf and Mafb overcoming the MDSC-mediated immunosuppressive microenvironment and enhancing PTX-Rg3-lipo's antitumor effect. Taken together, we supply substantial evidence for its advantageous bioavailability and safety in multiple animal models, including nonhuman primates, and Rg3-lipo's dual targeting of cancer cells and MDSCs. Further investigation regarding Rg3-lipo's druggability will be conducted in clinical trials.

Immune Implications of Cholesterol-Containing Lipid Nanoparticles

The majority of clinically approved nanoparticle-mediated therapeutics are lipid nanoparticles (LNPs), and most of these LNPs are liposomes containing cholesterol. LNP formulations significantly alter the drug pharmacokinetics (PK) due to the propensity of nanoparticles for uptake by macrophages. In addition to readily engulfing LNPs, the high expression of cholesterol hydroxylases and reactive oxygen species (ROS) in macrophages suggests that they will readily produce oxysterols from LNP-associated cholesterol. Oxysterols are a heterogeneous group of cholesterol oxidation products that have potent immune modulatory effects. Oxysterols are implicated in the pathogenesis of atherosclerosis and certain malignancies; they have also been found in commercial liposome preparations. Yet, the in vivo metabolic fate of LNP-associated cholesterol remains unclear. We review herein the mechanisms of cellular uptake, trafficking, metabolism, and immune modulation of endogenous nanometer-sized cholesterol particles (i.e., lipoproteins) that are also relevant for cholesterol-containing nanoparticles. We believe that it would be imperative to better understand the in vivo metabolic fate of LNP-associated cholesterol and the immune implications for LNP-therapeutics. We highlight critical knowledge gaps that we believe need to be addressed in order to develop safer and more efficacious lipid nanoparticle delivery systems.

Improved therapeutic index of the liposomal docetaxel-glutathione prepared by active click loading

The clinical usage of docetaxel (DTX) is severely hindered by the dose-limiting neutropenia and peripheral neurotoxicity of polysorbate 80-solubilized DTX injection, and there are no alternative formulations until now. In this study, we developed a new liposomal formulation of DTX to reduce its toxicities, accompanying with the greatly improved antitumor activity. The DTX was encapsulated into liposomes in the form of hydrophilic glutathione (GSH)-conjugated prodrugs using a click drug loading method, which achieved a high encapsulation efficiency (∼95 %) and loading capacity (∼30 % wt). The resulting liposomal DTX-GSH provided a sustained and efficient DTX release (∼50 % within 48 h) in plasma, resulting in a greatly improved antitumor activities as compared with that of polysorbate 80-solubilized DTX injection in the subcutaneous and orthotopic 4T1 breast tumor bearing mice. Even large tumors > 500 mm3 could be effectively inhibited and shrunk after the administration of liposomal DTX-GSH. More importantly, the liposomal DTX-GSH significantly decreased the neutropenia and peripheral neurotoxicity as compared with that of polysorbate 80-solubilized DTX injection at the equivalent dose. These data suggested that the liposomal DTX-GSH might become a superior alternative formulation to the commercial DTX injection.

Linoleate-pazopanib conjugation as active pharmacological ingredient to abolish hepatocellular carcinoma growth

Small molecule compounds targeting multiple kinases involved in neoangiogenesis have shown survival benefits in patients with unresectable hepatocellular carcinoma (HCC). Nonetheless, despite the beneficial effects of multikinase inhibitors (MKIs), a lack of boosting adjuvant limits their objective response rate. Lipid conjugates have been used to improve delivery efficacy or pharmaceutical benefits for decades. However, the feasibility of utilizing lipid-drug conjugates (LDCs) in HCC regimens remains untested. In this study, oral feeding of linoleate-fluorescein isothiocyanate conjugates showed that the compound was well distributed in a spontaneous HCC mouse model. Therefore, a rationale design was developed for chemically synthesizing a linoleate-pazopanib conjugate (LAPC). The LAPC showed a significantly improved cytotoxicity compared to the parental drug pazopanib. Pazopanib's angiogenic suppressing signals were not observed in LAPC-treated HCC cells, potentially suggesting an altered mechanism of action (MOA). In an efficacy trial comparing placebo, oral pazopanib, and LAPC treatments in the hepatitis B virus transgene-related spontaneous HCC mouse model (HBVtg-HCC), the LAPC treatment demonstrated superior tumor ablating capacity in comparison to both placebo and pazopanib treatments, without any discernible systemic toxicity. The LAPC exposure is associated with an apoptosis marker (Terminal deoxynucleotidyl transferase dUTP nick end labeling [TUNEL]) and an enhanced ferroptosis (glutathione peroxidase 4 [GPX4]) potential in HBVtg-HCC tumors. Therefore, the LAPC showed excellent HCC ablative efficacy with altered MOA. The molecular mechanisms of the LAPC and LDCs for HCC therapeutics are of great academic interest. Further comprehensive preclinical trials (e.g., chemical-manufacture-control, toxicity, distribution, and pharmacokinetics/pharmacodynamics) are expected.

Tumor microenvironment stimuli-responsive lipid-drug conjugates for cancer treatment

Lipid drug conjugates (LDCs) have attracted considerable attention in the fields of drug delivery and pharmacology due to their ability to target specific cells, increase drug solubility, reduce toxicity, and improve therapeutic efficacy. These unique features make LDCs promising candidates for the treatment cancer, inflammation, and infectious diseases. In fact, by choosing specific linkers between the lipid and drug molecules, stimuli-responsive LDCs can be designed to target cancer cells based on the unique properties of the tumor microenvironment. Despite the fact that many reviews have described LDCs, few articles have focused on tumor microenvironmental stimuli-responsive LDCs for cancer treatment. Therefore, the key elements of these types of LDCs in cancer treatment will be outlined and discussed in this paper. Our paper goes into detail on the concepts and benefits of LDCs, the various types of tumor microenvironment stimuli-responsive LDCs (such as pH, redox, enzyme, or reactive oxygen species-responsive LDCs), and the current status of LDCs in clinical trials.

Dual targeted zeolitic imidazolate framework nanoparticles for treating metastatic breast cancer and inhibiting bone destruction

Tumor bone metastasis is still difficult to cure despite the development of various treatment strategies. Drug delivery systems can improve the poor biological distribution of anticancer drugs in tumors. But only a very small number of nanoparticles can cross the physiological barrier to reach the tumor. In addition, the progression of bone metastasis is influenced by tumor cells, osteoclasts and bone matrix. To address these problems, a bone and tumor dual targeted nanocarrier was developed by utilizing NF-κB inhibitor loaded into zeolitic imidazolate framework-8 (ZIF-8) (CZ), which was then coated with hyaluronic acid/alendronate (HA/ALN). The CZ prepared by two-step method had high loading capacity, and the loading efficiency of Cur was to be 47.55 ± 4.03%. HA/ALN functionalization avoided explosive release of reagents and improved the stability of nanoparticles. The dual targeted ZIF-8 nanoparticle (CZ@HA/ALN) had a pH-triggered drug release performance, which effectively inhibited breast cancer cells growth and osteoclastogenesis in vitro. Uptake experiments showed that the conjugation of ALN with HA did not affect targeting ability of HA. Moreover, HA/ALN functionalized nanoparticles were more aggregated at bone metastasis sites than HA functionalized nanoparticles. CZ@HA/ALN could block the PD-1 immune check point, leading to Raw 264.7 cells differentiation into anti-tumor macrophage rather than osteoclast. The antitumor experiments in vivo exhibited that the dual targeted ZIF-8 nanoparticle effectively inhibited bone resorption and tumor progress, thereby improving the bone microenvironment. Therefore, this single but versatile nanoparticle provided a promising therapeutic scheme for bone metastasis treatment.

Updates on Responsive Drug Delivery Based on Liposome Vehicles for Cancer Treatment

Liposomes are well-known nanoparticles with a non-toxic nature and the ability to incorporate both hydrophilic and hydrophobic drugs simultaneously. As modern drug delivery formulations are produced by emerging technologies, numerous advantages of liposomal drug delivery systems over conventional liposomes or free drug treatment of cancer have been reported. Recently, liposome nanocarriers have exhibited high drug loading capacity, drug protection, improved bioavailability, enhanced intercellular delivery, and better therapeutic effect because of resounding success in targeting delivery. The site targeting of smart responsive liposomes, achieved through changes in their physicochemical and morphological properties, allows for the controlled release of active compounds under certain endogenous or exogenous stimuli. In that way, the multifunctional and stimuli-responsive nanocarriers for the drug delivery of cancer therapeutics enhance the efficacy of treatment prevention and fighting over metastases, while limiting the systemic side effects on healthy tissues and organs. Since liposomes constitute promising nanocarriers for site-targeted and controlled anticancer drug release, this review focuses on the recent progress of smart liposome achievements for anticancer drug delivery applications.

Indocarbocyanine nanoparticles extravasate and distribute better than liposomes in brain tumors

Glioblastoma (GBM) is the most devastating and aggressive brain tumor in adults. Hidden behind the blood-brain and blood-tumor barriers (BBTB), this invasive type of brain tumor is not readily accessible to nano-sized particles. Here we demonstrate that fluorescent indocarbocyanine lipids (ICLs: DiD, DiI) formulated in PEGylated lipid nanoparticle (PLN) exhibit highly efficient penetration and accumulation in GBM. PLN-formulated ICLs demonstrated more efficient penetration in GBM spheroids and organoids in vitro than liposomal ICLs. Over 82% of the tumor's extravascular area was positive for ICL fluorescence in the PLN group versus 13% in the liposomal group just one hour post-systemic injection in the intracranial GBM model. Forty-eight hours post-injection, PLN-formulated ICLs accumulated in 95% of tumor myeloid-derived suppressor cells and macrophages, 70% of tumor regulatory T cells, 50% of tumor-associated microglia, and 65% of non-immune cells. PLN-formulated ICLs extravasated better than PEGylated liposomal doxorubicin and fluorescent dextran and efficiently accumulated in invasive tumor margins and brain-invading cells. While liposomes were stable in serum in vitro and in vivo, PLNs disassembled before entering tumors, which could explain the differences in their extravasation efficiency. These findings offer an opportunity to improve therapeutic cargo delivery to invasive GBM.

Ex-vivo activation of a liposomal prodrug of mitomycin C by human tumors

PURPOSE

To examine the ex- vivo ability of explanted human tumors and normal tissue to activate liposomal mitomycin C lipidic prodrug (MLP) by releasing the active free drug form, mitomycin C (MMC).

METHODS

We tested conversion of MLP to MMC in an ex vivo assay using explanted tissues obtained during routine surgery to remove primary tumors or metastases. Tumor and adjacent normal tissue were obtained from freshly explanted tumors and were immediately deep frozen at - 70 °C. On test day, the fragments were thawed, homogenized and incubated in the presence of a fixed amount of liposomal MLP at 37 °C for 1 h. We measured MLP and its rate of conversion to MMC by HPLC. Controls included plasma, malignant effusions, red blood cells, tumor cell lines, mouse liver, and buffer with dithiothreitol, a potent reducing agent.

RESULTS

Most patients tested (16/20) were diagnosed with colo-rectal carcinoma. The average fraction of MLP cleaved per 100-mg tumor tissue (21.1%, SEM = 1.8) was greater than per 100-mg normal tissue (16.6%, SEM = 1.3). When the tumor and normal tissue samples were paired by patient, the difference was statistically significant (p = 0.022, paired t test). Biological fluids did not activate liposomal MLP, while normal liver tissue strongly does. Interestingly, the omental fatty tissue also greatly activated MLP.

CONCLUSIONS

Tumor tissue homogenates activate MLP with greater efficiency than the surrounding normal tissues, but far less than liver and adipose tissue. These observations demonstrate the bioavailability of liposomal MLP in human tumors, and its pharmacologic potential in cancer therapy.

A Review of Liposomes as a Drug Delivery System: Current Status of Approved Products, Regulatory Environments, and Future Perspectives

Liposomes have been considered promising and versatile drug vesicles. Compared with traditional drug delivery systems, liposomes exhibit better properties, including site-targeting, sustained or controlled release, protection of drugs from degradation and clearance, superior therapeutic effects, and lower toxic side effects. Given these merits, several liposomal drug products have been successfully approved and used in clinics over the last couple of decades. In this review, the liposomal drug products approved by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) are discussed. Based on the published approval package in the FDA and European public assessment report (EPAR) in EMA, the critical chemistry information and mature pharmaceutical technologies applied in the marketed liposomal products, including the lipid excipient, manufacturing methods, nanosizing technique, drug loading methods, as well as critical quality attributions (CQAs) of products, are introduced. Additionally, the current regulatory guidance and future perspectives related to liposomal products are summarized. This knowledge can be used for research and development of the liposomal drug candidates under various pipelines, including the laboratory bench, pilot plant, and commercial manufacturing.

Lipophilic Conjugates of Drugs: A Tool to Improve Drug Pharmacokinetic and Therapeutic Profiles

Lipophilic conjugates (LCs) of small molecule drugs have been used widely in clinical and pre-clinical studies to achieve a number of pharmacokinetic and therapeutic benefits. For example, lipophilic derivatives of drugs are employed in several long acting injectable products to provide sustained drug exposure for hormone replacement therapy and to treat conditions such as neuropsychiatric diseases. LCs can also be used to modulate drug metabolism, and to enhance drug permeation across membranes, either by increasing lipophilicity to enhance passive diffusion or by increasing protein-mediated active transport. Furthermore, such conjugation strategies have been employed to promote drug association with endogenous macromolecular carriers (e.g. albumin and lipoproteins), and this in turn results in altered drug distribution and pharmacokinetic profiles, where the changes can be 'general' (e.g. prolonged plasma half-life) or 'specific' (e.g. enhanced delivery to specific tissues in parallel with the macromolecular carriers). Another utility of LCs is to enhance the encapsulation of drugs within engineered nanoscale drug delivery systems, in order to best take advantage of the targeting and pharmacokinetic benefits of nanomedicines. The current review provides a summary of the mechanisms by which lipophilic conjugates, including in combination with delivery vehicles, can be used to control drug delivery, distribution and therapeutic profiles. The article is structured into sections which highlight a specific benefit of LCs and then demonstrate this benefit with case studies. The review attempts to provide a toolbox to assist researchers to design and optimise drug candidates, including consideration of drug-formulation compatibility.

Progress in nanostructure understanding of edible crystalline fats and their application in nano-delivery systems: Cocoa butter as a model

Nucleation and crystal growth of edible fats at the nanoscale have received little attention due to analytical limitations. A key factor to modify the properties of edible fats is nanostructure understanding. Progress within the last years will be presented, including analytical techniques used to investigate fat crystallization. Cocoa butter has been the subject of several works due to its properties and its high impact on chocolate manufacturing. Moreover, this vegetable fat has been used as the solid lipid component in nano delivery systems. Since nanoplatelet is the smallest unit in crystalline fats, and the nanoscale is influenced by supersaturation, temperature, shear fields, and surfactants, nanostructure engineering is possible. On its part, cocoa butter has been included in innovative delivery systems along the last years. This review will highlight main results and challenges on these topics.

Direct comparison of two kinds of linoleic acid-docetaxel derivatives: in vitro cytotoxicity and in vivo antitumor activity

Rational designed lipid-drug derivatives provide a favorable approach to improve the druggability of highly hydrophobic prototypes. It has been regarded as common sense that good cytotoxicity is the guarantee of superior anticancer efficacy for candidate derivatives screening. However, does it apply to lipid-drug conjugate-based self-assembled nanoparticles? Here, we established the above two derivatives and a non-correlation between the cytotoxic activity in vitro and drug efficacy in vivo was found. The IC₅₀ of DSL NPs (DTX-S-LA nanoparticles) and DL NPs (DTX-LA nanoparticles) were 4.02 and 209.6 ng/mL (DTX equivalent concentration), respectively. However, DL NPs unexpectedly showed stronger tumor inhibition abilities than DSL NPs. To explain the non-positive correlation between cytotoxicity and anticancer efficacy, more experiments were carried out in depth. Remarkably, the drug release studies in blood and PK study both suggested that the DL NPs were more stable to remain the structural integrity in circulation, which resulted in more accumulation in tumor sites. As verified by the bio-distribution study, DL NPs performed a superior target effect than DSL NPs in tumors. Our data indicated that the biological fates of so-called smart bond inserted derivatives in vivo are complicated; thus, simple cytotoxicity is not enough for derivatives screening, and the comprehensive understanding of both in vitro and in vivo behaviors is essential.

Liposomal Formulation of a Melphalan Lipophilic Prodrug: Studies of Acute Toxicity, Tolerability, and Antitumor Efficacy

BACKGROUND

Recently we developed a scalable scheme of synthesis of melphalan ester conjugate with 1,2-dioleoyl-sn-glycerol (MlphDG) and a protocol for the fabrication of its lyophilized liposomal formulation.

OBJECTIVE

Herein we compared this new convenient in use formulation of MlphDG with parent drug Alkeran® in rats concerning several toxicological parameters and evaluated its antitumor efficacy in the model of breast cancer in mice.

METHOD

Liposomes of approximately 100 nm in diameter, consisting of egg phosphatidylcholine, soybean phosphatidylinositol, and MlphDG, or placebo liposomes without the drug were produced by extrusion and lyophilized. Alkeran® or liposomes recovered by the addition of water were injected into the tail vein of animals. Clinical examination of rats consisted of detailed inspection of the behavior, general status, and hematological parameters. Mice with transplanted breast cancer WNT-1 were subjected to multiple treatments with the drugs; tumor growth inhibition was assessed, together with cellular immunity parameters.

RESULTS

Liposomes showed approximately two times lower acute toxicity and better tolerability than Alkeran® in terms of behavioral criteria. The toxic effects of liposomes on hemopoiesis were manifested at higher doses than in the case of Alkeran®, proportionally to the difference in LD50 values. The formulation inhibited tumor growth significantly more effectively than Alkeran®, delaying the start of the exponential growth phase and exhibiting no additional toxic effects toward bone marrow.

CONCLUSION

Lower toxicity of the liposomal formulation of MlphDG promises improved quality of life for cancer patients in need of treatment with melphalan. Presumably, the list of indications for melphalan therapy could be extended.

Phosphatidylinositol Stabilizes Fluid-Phase Liposomes Loaded with a Melphalan Lipophilic Prodrug

Previously, a liposomal formulation of a chemotherapeutic agent melphalan (Mlph) incorporated in a fluid lipid bilayer of natural phospholipids in the form of dioleoylglyceride ester (MlphDG) was developed and the antitumor effect was confirmed in mouse models. The formulation composed of egg phosphatidylcholine (ePC), soybean phosphatidylinositol (PI), and MlphDG (8:1:1, by mol) showed stability in human serum for at least 4–5 h. On the contrary, replacing PI with pegylation of the liposomes, promoted fast dissociation of the components from the bilayer. In this work, interactions of MlphDG-liposomes with the most abundant plasma protein—albumin—in function of the presence of PI in the formulation were explored using Fourier transform infrared spectroscopy. The release of MlphDG from the liposomes was studied by asymmetrical flow field-flow fractionation (AF4) using micelles formed by a polyethylene glycol conjugate with phosphatidylethanolamine to mimic the physiological lipid sink like lipoproteins. Our results show that PI actually protects the membrane of MlphDG-liposomes from the protein penetration, presumably due to pairing between the positively charged MlphDG and negatively charged PI, which compensates for the heterogeneity of the lipid bilayer. The AF4 technique also evidences high stability of the formulation as a drug carrier.

Enhancing the preservation of liposomes: The role of cryoprotectants, lipid formulations and freezing approaches

In the last decades, liposomes acquired a striking success in the biomedical field thanks to their biocompatibility and drug delivery ability. Many liposomal drug formulations have been already approved by the Food and Drug Administration (FDA) and used for the treatment of a wide range of pathologies with or without further engineering. Their clinical application requires strict compliance with high standard quality rules, and it is crucial to employ storage methods that do not affect the integrity of the vesicles and preventing the leakage of their cargo. In this work, the design of a suitable formulation for freeze-drying had been investigated for two different liposomes, DOPC-DOTAP and the PEGylated counterpart, DOPC-DOTAP-DSPE-PEG. The role of various cryoprotectants was evaluated paying attention to their ability to preserve the structural integrity of liposomes. At first, the study was focused on freezing and two methodologies were investigated, quenching in liquid nitrogen and shelf-ramped freezing. This analysis showed that the disaccharides (cellobiose, glucose, lactose, sucrose, and trehalose) and the polyol (mannitol) protected successfully the integrity of liposomes, while during the process, in the presence of a surfactant, liposomes were strongly damaged and fragmented by the ice crystals. Furthermore, the choice of the rate of freezing depended on the different compositions of the lipid bilayer. Finally, the effects of lyophilization on liposomes with and without additives were studied; cellobiose, lactose and trehalose showed encouraging results for the maintenance of the morpho-functional parameters of liposomes during the entire freeze-drying process.

Nanomedicine Reformulation of Chloroquine and Hydroxychloroquine

The chloroquine family of antimalarials has a long history of use, spanning many decades. Despite this extensive clinical experience, novel applications, including use in autoimmune disorders, infectious disease, and cancer, have only recently been identified. While short term use of chloroquine or hydroxychloroquine is safe at traditional therapeutic doses in patients without predisposing conditions, administration of higher doses and for longer durations are associated with toxicity, including retinotoxicity. Additional liabilities of these medications include pharmacokinetic profiles that require extended dosing to achieve therapeutic tissue concentrations. To improve chloroquine therapy, researchers have turned toward nanomedicine reformulation of chloroquine and hydroxychloroquine to increase exposure of target tissues relative to off-target tissues, thereby improving the therapeutic index. This review highlights these reformulation efforts to date, identifying issues in experimental designs leading to ambiguity regarding the nanoformulation improvements and lack of thorough pharmacokinetics and safety evaluation. Gaps in our current understanding of these formulations, as well as recommendations for future formulation efforts, are presented.

Recent Progress in Bioconjugation Strategies for Liposome-Mediated Drug Delivery

In nanoparticle (NP)-mediated drug delivery, liposomes are the most widely used drug carrier, and the only NP system currently approved by the FDA for clinical use, owing to their advantageous physicochemical properties and excellent biocompatibility. Recent advances in liposome technology have been focused on bioconjugation strategies to improve drug loading, targeting, and overall efficacy. In this review, we highlight recent literature reports (covering the last five years) focused on bioconjugation strategies for the enhancement of liposome-mediated drug delivery. These advances encompass the improvement of drug loading/incorporation and the specific targeting of liposomes to the site of interest/drug action. We conclude with a section highlighting the role of bioconjugation strategies in liposome systems currently being evaluated for clinical use and a forward-looking discussion of the field of liposomal drug delivery.

Stimuli-responsive phospholipid-drug conjugates (PDCs)-based nanovesicles for drug delivery and theranostics

Liposomes represent one of the most successful nano-drug delivery systems among enormous nano-carriers. Although great progress has been made in conventional liposomes, the emerging shortcomings still impair the therapeutic index. The proposal of stimuli-responsive phospholipid-drug conjugates (PDCs)-based nanovesicles solves the challenges that conventional liposomes are faced with, showing great potential for cancer diagnosis and therapy. Herein, we intend to overview the current progress and unique advantages of stimuli-responsive PDCs-based nanovesicles. First, the challenges of conventional liposomes and the development of PDCs-based nanovesicles are summarized. Next, the stimuli-responsive elements used in current stimuli-responsive PDCs-based nanovesicles are outlined. Then, the unique superiorities of stimuli-responsive PDCs-based nanovesicles for drug delivery and theranostics are highlighted in detail. Finally, the future opportunities and challenges of stimuli-responsive PDCs-based nanovesicles for clinical translation are put forward.

Construction of chlorogenic acid-containing liposomes with prolonged antitumor immunity based on T cell regulation

As a potential cancer immunotherapeutic agent, chlorogenic acid (CHA) has entered phase II clinical trials in China as a lyophilized powder formulation for treating glioma. However, the in vivo instability of CHA necessitates daily intramuscular injections, resulting in patient noncompliance. In this study, CHA-phospholipid complex (PC)-containing PEGylated liposomes (CHA-PC PEG-Lipo, named as CPPL), with CHA-PC as the drug intermediate, were prepared to lower the administration frequency. CPPL demonstrated excellent physicochemical properties, enhanced tumor accumulation, and inhibited tumor growth even when the administration interval was prolonged to 4 days when compared to a CHA solution and CHA-PC loaded liposomes (CHA-PC Lipo, labeled as CPL), both of which only demonstrated antitumor efficacy with once-daily administration. Further evaluation of the in vivo antitumor immune mechanism suggested that the extended antitumor immune efficacy of CPPL could be attributed to its distinct immune-stimulating mechanism when compared with CHA solution and CPL, such as stimulating both CD4⁺ and CD8⁺ T cell infiltration, inhibiting myeloid-derived suppressor cell expression, reducing the expression of Th2 related factors, and notably, increasing the memory T cells in tumor tissues. This CHA-containing formulation could reduce the frequency of in vivo CHA administration during cancer treatment via T cells, especially memory T cell regulation.

Emerging insights on drug delivery by fatty acid mediated synthesis of lipophilic prodrugs as novel nanomedicines

Many drug molecules that are currently in the market suffer from short half-life, poor absorption, low specificity, rapid degradation, and resistance development. The design and development of lipophilic prodrugs can provide numerous benefits to overcome these challenges. Fatty acids (FAs), which are lipophilic biomolecules constituted of essential components of the living cells, carry out many necessary functions required for the development of efficient prodrugs. Chemical conjugation of FAs to drug molecules may change their pharmacodynamics/pharmacokinetics in vivo and even their toxicity profile. Well-designed FA-based prodrugs can also present other benefits, such as improved oral bioavailability, promoted tumor targeting efficiency, controlled drug release, and enhanced cellular penetration, leading to improved therapeutic efficacy. In this review, we discuss diverse drug molecules conjugated to various unsaturated FAs. Furthermore, various drug-FA conjugates loaded into various nanostructure delivery systems, including liposomes, solid lipid nanoparticles, emulsions, nano-assemblies, micelles, and polymeric nanoparticles, are reviewed. The present review aims to inspire readers to explore new avenues in prodrug design based on the various FAs with or without nanostructured delivery systems.

Construction a Long-Circulating Delivery System of Liposomal Curcumin by Coating Albumin

Although the bioavailability and stability of curcumin can be greatly improved by liposomes encapsulation, its application is still limited due to the short circulating time. In this present work, we aim to construct a long-circulating delivery system of liposomal curcumin (Cur-Lips) by coating bovine serum albumin (BSA), namely, BSA-coated liposomal curcumin (BSA-Cur-Lips). The effects of coating albumin on the physicochemical properties of Cur-Lips were investigated. It was found that BSA-Cur-Lips was more spherical, more homogeneous in size, and significantly larger than Cur-Lips. Combining sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Coomassie bright blue staining, and X-ray photoelectron spectroscopy analysis (XPS), we confirmed that albumin molecules were stably located on the surface of BSA-Cur-Lips. In addition, the impacts of the coating albumin on the Cur-Lips release and phagocytosis by mouse macrophages Raw264.7 in vitro were investigated. We found that no significant initial burst drug release effect was observed for both Cur-Lips and BSA-Cur-Lips and the presence of albumin can enhance the liposome structure stability and slow down the release of Cur. More importantly, the macrophage phagocytosis of Cur-Lips was significantly reduced after coating albumin. In conclusion, coating albumin is a promising approach for developing a long-circulating delivery system of liposomal curcumin, and its properties including low phagocytosis, slow drug release, enhanced stability, and nontoxicity give this system great prospects for practical use.

Following the Fate of Dye-Containing Liposomes In Vitro

The rather limited success of translation from basic research to clinical application has been highlighted as a major issue in the nanomedicine field. To identify the factors influencing the applicability of nanosystems as drug carriers and potential nanomedicine, we focused on following their fate through fluorescence-based assays, namely flow cytometry and imaging. These methods are often used to follow the nanocarrier internalization and targeting; however, the validity of the obtained results strictly depends on how much the nanosystem’s fate can be inferred from the fate of fluorescent dyes. To evaluate the parameters that affect the physicochemical and biological stability of the labeled nanosystems, we studied the versatility of two lipid dyes, TopFluor^®-PC and Cy5-DSPE, in conventional liposomes utilizing well-defined in vitro assays. Our results suggest that the dye can affect the major characteristics of the system, such as vesicle size and zeta-potential. However, a nanocarrier can also affect the dye properties. Medium, temperature, time, fluorophore localization and its concentration, as well as their interplay, affect the outcome of tracing experiments. Therefore, an in-depth characterization of the labeled nanosystem should be fundamental to understand the conditions that validate the results within the screening process in optimization of nanocarrier.

Lipid Vesicles Loaded with an HIV-1 Fusion Inhibitor Peptide as a Potential Microbicide

The effective use of fusion inhibitor peptides against cervical and colorectal infections requires the development of sustained release formulations. In this work we comparatively study two different formulations based on polymeric nanoparticles and lipid vesicles to propose a suitable delivery nanosystem for releasing an HIV-1 fusion inhibitor peptide in vaginal mucosa. Polymeric nanoparticles of poly-d,l-lactic-co-glycolic acid (PLGA) and lipid large unilamellar vesicles loaded with the inhibitor peptide were prepared. Both formulations showed average sizes and polydispersity index values corresponding to monodisperse systems appropriate for vaginal permeation. High entrapment efficiency of the inhibitor peptide was achieved in lipid vesicles, which was probably due to the peptide's hydrophobic nature. In addition, both nanocarriers remained stable after two weeks stored at 4 °C. While PLGA nanoparticles (NPs) did not show any delay in peptide release, lipid vesicles demonstrated favorably prolonged release of the peptide. Lipid vesicles were shown to improve the retention of the peptide on ex vivo vaginal tissue in a concentration sufficient to exert its pharmacological effect. Thus, the small size of lipid vesicles, their lipid-based composition as well as their ability to enhance peptide penetration on vaginal tissue led us to consider this formulation as a better nanosystem than polymeric nanoparticles for the sustained delivery of the HIV-1 fusion inhibitor peptide in vaginal tissues.

Nanocarriers for the Delivery of Medical, Veterinary, and Agricultural Active Ingredients

Nanocarrier-based delivery systems can be used to increase the safety and efficacy of active ingredients in medical, veterinary, or agricultural applications, particularly when such ingredients are unstable, sparingly soluble, or cause off-target effects. In this review, we highlight the diversity of nanocarrier materials and their key advantages compared to free active ingredients. We discuss current trends based on peer-reviewed research articles, patent applications, clinical trials, and the nanocarrier formulations already approved by regulatory bodies. Although most nanocarriers have been engineered to combat cancer, the number of formulations developed for other purposes is growing rapidly, especially those for the treatment of infectious diseases and parasites affecting humans, livestock, and companion animals. The regulation and prohibition of many pesticides have also fueled research to develop targeted pesticide delivery systems based on nanocarriers, which maximize efficacy while minimizing the environmental impact of agrochemicals.

Mechanistic and therapeutic study of novel anti-tumor function of natural compound imperialine for treating non-small cell lung cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Bulbus Fritillaria cirrhosa D. Don (BFC) is a Chinese traditional herbal medicine that has long been used as an indispensable component in herbal prescriptions for bronchopulmonary diseases due to its well-established strong anti-inflammation and pulmonary harmonizing effects. Interestingly, there are few case reports in traditional Chinese medicine available where they found it to contribute in anti-tumor therapies. Imperialine is one of the most favored active substances extracted from BFC and has been widely recognized as an anti-inflammatory agent.

AIM OF THE STUDY

The aim of the current work is to provide first-hand evidences both in vitro and in vivo showing that imperialine exerts anti-cancer effects against non-small cell lung cancer (NSCLC), and to explore the molecular mechanism of this anti-tumor activity. It is also necessary to examine its systemic toxicity, and to investigate how to develop strategies for feasible clinical translation of imperialine.

MATERIALS AND METHODS

To investigate anti-NSCLC efficacy of imperialine using both in vitro and in vivo methods where A549 cell line were chosen as in vitro model NSCLC cells and A549 tumor-bearing mouse model was constructed for in vivo study. The detailed underlying anti-cancer mechanism has been systematically explored for the first time through a comprehensive set of molecular biology methods mainly including immunohistochemistry, western blot and enzyme-linked immunosorbent assays. The toxicity profile of imperialine treatments were evaluated using healthy nude mice by examining hemogram and histopathology. An imperialine-loaded liposomal drug delivery system was developed using thin film hydration method to evaluate target specific delivery.

RESULTS

The results showed that imperialine could suppress both NSCLC tumor and associated inflammation through an inflammation-cancer feedback loop in which NF-κB activity was dramatically inhibited by imperialine. The NSCLC-targeting liposomal system was successfully developed for targeted drug delivery. The developed platform could favorably enhance imperialine cellular uptake and in vivo accumulation at tumor sites, thus improving overall anti-tumor effect. The toxicity assays revealed imperialine treatments did not significantly disturb blood cell counts in mice or exert any significant damage to the main organs.

CONCLUSIONS

Imperialine exerts anti-cancer effects against NSCLC both in vitro and in vivo, and this previously unknown function is related to NF-κB centered inflammation-cancer feedback loop. Imperialine mediated anti-cancer activity is not through cytotoxicity and exhibit robust systemic safety. Furthermore, the liposome-based system we commenced would dramatically enhance therapeutic effects of imperialine while exhibiting extremely low side effects both on cellular and in NSCLC model. This work has identified imperialine as a promising novel anti-cancer compound and offered an efficient target-delivery solution that greatly facilitate practical use of imperialine.

Immunological and Toxicological Considerations for the Design of Liposomes

Liposomes hold great potential as gene and drug delivery vehicles due to their biocompatibility and modular properties, coupled with the major advantage of attenuating the risk of systemic toxicity from the encapsulated therapeutic agent. Decades of research have been dedicated to studying and optimizing liposomal formulations for a variety of medical applications, ranging from cancer therapeutics to analgesics. Some effort has also been made to elucidate the toxicities and immune responses that these drug formulations may elicit. Notably, intravenously injected liposomes can interact with plasma proteins, leading to opsonization, thereby altering the healthy cells they come into contact with during circulation and removal. Additionally, due to the pharmacokinetics of liposomes in circulation, drugs can end up sequestered in organs of the mononuclear phagocyte system, affecting liver and spleen function. Importantly, liposomal agents can also stimulate or suppress the immune system depending on their physiochemical properties, such as size, lipid composition, pegylation, and surface charge. Despite the surge in the clinical use of liposomal agents since 1995, there are still several drawbacks that limit their range of applications. This review presents a focused analysis of these limitations, with an emphasis on toxicity to healthy tissues and unfavorable immune responses, to shed light on key considerations that should be factored into the design and clinical use of liposomal formulations.

Improving the Stability of Liposomal Curcumin by Adjusting the Inner Aqueous Chamber pH of Liposomes

Curcumin (CURC) is a hydrophobic molecule and its water solubility can be greatly improved by liposome encapsulation. However, investigations on the stability of pH-sensitive molecules incorporated into liposomal membranes are limited. In this study, CURC-loaded liposomes with varied internal pH values (pH 2.5, 5.0, or 7.4) were prepared and designated as CURC-LP (pH 2.5), CURC-LP (pH 5.0), and CURC-LP (pH 7.4). Physical properties including particle size, ζ-potential, morphology, entrapment efficiency, and physical stabilities of these CURC-LPs were assessed. In addition, the chemical stability of liposomal CURC to different external physiological environments and internal microenvironmental pH levels were investigated. We found that among these CURC-LPs, CURU-LP (pH 2.5) has the highest entrapment efficiency (73.7%), the best physical stabilities, and the slowest release rate in vitro. Liposomal CURC remains more stable in an acid external environment. In the physiological environment, the chemical stability of liposomal CURC is microenvironmental pH-dependent. In conclusion, we prove that the stability of liposomal CURC is external physiological environment- and internal microenvironmental pH-dependent. These findings suggest that creating an acidic microenvironment in the internal chamber of liposomes is beneficial to the stability of liposomal CURC, as well as for other pH-sensitive molecules.

Development of Promitil®, a lipidic prodrug of mitomycin c in PEGylated liposomes: From bench to bedside

Several liposome products have been approved for the treatment of cancer. In all of them, the active agents are encapsulated in the liposome water phase passively or by transmembrane ion gradients. An alternative approach in liposomal drug delivery consists of chemically modifying drugs to form lipophilic prodrugs with strong association to the liposomal bilayer. Based on this approach, we synthesized a mitomycin c-derived lipidic prodrug (MLP) which is entrapped in the bilayer of PEGylated liposomes (PL-MLP, Promitil®), and activated by thiolytic cleavage. PL-MLP is stable in plasma with thiolytic activation of MLP occurring exclusively in tissues and is more effective and less toxic than conventional chemotherapy in various tumor models. PL-MLP has completed phase I clinical development where it has shown a favorable safety profile and a 3-fold reduction in toxicity as compared to free mitomycin c. Clinical and pharmacokinetic studies in patients with advanced colo-rectal carcinoma have indicated a significant rate of disease stabilization (39%) in this chemo-refractory population and significant prolongation of median survival in patients attaining stable disease (13.9 months) versus progressive disease patients (6.35 months). The pharmacokinetics of MLP was typically stealth with long T½ (~1 day), slow clearance and small volume of distribution. Interestingly, a longer T½, and slower clearance were both correlated with disease stabilization and longer survival. This association of pharmacokinetic parameters with patient outcome suggests that arrest of tumor growth is related to the enhanced tumor localization of long-circulating liposomes and highlights the importance of personalized pharmacokinetic evaluation in the clinical use of nanomedicines. Another important area where PL-MLP may have an added value is in chemoradiotherapy, where it has shown a strong radiosensitizing effect in animal models based on a unique mechanism of enhanced prodrug activation and encouraging results in early human testing.

Nanomedicine review: clinical developments in liposomal applications

Background

In recent years, disease treatment has evolved strategies that require increase in pharmaceutical agent’s efficacy and selectivity while decreasing their toxicity in normal tissues. These requirements have led to the development of nanoscale liposome systems for drug release. This review focuses on lipid features, pharmacological properties of liposomal formulations and the clinical studies of their application.

Main body

Several lipids are available, but their properties could affect pharmacological or clinical efficiency of drug formulations. Many liposomal formulations have been developed and are currently on the market. Proper selection of lipid is essential for the pharmacological effect to be improved. Most of the formulations use mainly zwitterionic, cationic or anionic lipids, PEG and/or cholesterol, which have different effects on stability, pharmacokinetics and delivery of the drug formulation. Clinical trials have shown that liposomes are pharmacologically and pharmacokinetically more efficient than drug-alone formulations in treating acute myeloid leukemia, hepatitis A, pain management, ovary, gastric breast and lung cancer, among others.

Conclusion

Liposomal formulations are less toxic than drugs alone and have better pharmacological parameters. Although they seem to be the first choice for drug delivery systems for various diseases, further research about dosage regimen regarding dose and time needs to be carried out.

Integrating Nanotechnology into Cancer Care

Research activity in medical and cancer nanotechnology has grown dramatically over the past 15 years. The field has become a cradle of multidisciplinary investigations bringing together physicists, chemists, and engineers working with clinicians and biologists to address paramount problems in cancer care and treatment. Some have argued that the explosion in the number of research papers has not been followed by sufficient clinical activity in nanomedicine. However, three new nanodrugs have now been approved by the U.S. Food and Drug Administration (FDA) in the past three years, confirming the validity of nanotechnology approaches in cancer. Excitingly, translational pipelines contain several additional intriguing candidates. In this Nano Focus article, we discuss potential barriers inhibiting further incorporation of nanomedicines into patient care, possible strategies to overcome these barriers, and promising new directions in cancer interventions based on nanotechnology. Insights presented herein are outcomes of discussions held at a recent strategic workshop hosted by the National Cancer Institute (NCI), which brought together research, clinical, and commercial leaders of the nanomedicine field.

Drug-Lipid Conjugates for Enhanced Oral Drug Delivery

Oral drug delivery route is one of the most convenient and extensively utilised routes for drug administration. But there exists class of drugs which exhibit poor bioavailability on oral drug administration. Designing of drug-lipid conjugates (DLCs) is one of the rationale strategy utilised in overcoming this challenge. This review extensively covers the various dimensions of drug modification using lipids to attain improved oral drug delivery. DLCs help in improving oral delivery by providing benefits like improved permeability, stability in gastric environment, higher drug loading in carriers, formation of self-assembled nanostructures, etc. The clinical effectiveness of DLCs is highlighted from available marketed drug products along with many DLCs in phase of clinical trials. Conclusively, this drug modification strategy can potentially help in augmenting oral drug delivery in future.

Antitumor activity of the bioreductive prodrug 3-(2-nitrophenyl) propionic acid-paclitaxel nanoparticles (NPPA-PTX NPs) on MDA-MB-231 cells: in vitro and in vivo

Background

3-(2-Nitrophenyl) propionic acid-paclitaxel (NPPA-PTX) is a paclitaxel (PTX) bioreductive prodrug synthesized by our lab. We hypothesize that NPPA-PTX can self-assemble to form nanoparticles (NPs).

Materials and methods

In the present research, the theoretical partition coefficient (XlogP) and Hansen solubility parameters of NPPA-PTX were calculated. NPPA-PTX nanoparticles prepared by NPPA-PTX and DSPE-PEG (NPPA-PTX:DSPE-PEG =1:0.1, w/w) (NPPA-PTX@PEG NPs) were prepared and characterized. The cellular uptake, in vitro antitumor activity, in vivo targeting effect, tumor distribution, in vivo antitumor activity, and safety of NPPA-PTX@PEG NPs were investigated.

Results

Our results indicate that NPPA-PTX can self-assemble to form NPPA-PTX@PEG NPs. Both the cellular uptake and safety of NPPA-PTX@PEG NPs were higher than those of Taxol. NPPA-PTX@PEG NPs could target tumor tissues by a passive targeting effect. In tumor tissues, NPPA-PTX@PEG NPs could completely transform into active PTX. The in vivo antitumor activity of NPPA-PTX@PEG NPs was confirmed in MDA-MB-231 tumor-bearing nude mice.

Conclusion

The bioreductive prodrug NPPA-PTX could self-assemble to form NPs. The safety and antitumor activity of NPPA-PTX@PEG were confirmed in our in vitro and in vivo experiments. The NPPA-PTX@PEG NPs developed in this study could offer a new way of preparing bioreductive prodrug, self-assembled NPs suitable for antitumor therapy.

Novel SN38 derivative-based liposome as anticancer prodrug: an in vitro and in vivo study

Background

Many novel drug delivery systems have been extensively studied to exploit the full therapeutic potential of SN38, which is one of the most potent antitumor analogs of camptothecins (CPTs), whose clinical application is seriously hindered by poor water solubility, low plasmatic stability, and severe toxicity, but results are always unsatisfactory.

Methods

In this study, combining the advantages of prodrug and nanotechnology, a lipophilic prodrug of SN38, SN38-PA, was developed by conjugating palmitic acid to SN38 via ester bond at C₁₀ position, and then the lipophilic prodrug was encapsulated into a long-circulating liposomal carrier by film dispersion method.

Results

The SN38-PA liposomes were characterized as follows: an average particle size of 80.13 nm, an average zeta potential of -33.53 mv, and the entrapment efficiency of 99%. Compared with CPT-11, SN38-PA liposome was more stable in close lactone form, more efficient in conversion rate to SN38, and more potent in cytotoxicity against tumor cells. Pharmacokinetic study showed that SN38-PA liposome had significantly enhanced plasma half-life (t_1/2) value of SN38 and increased area under the curve (AUC) of SN38, which was 7.5-fold higher than that of CPT-11. Biodistribution study showed that SN38-PA liposome had more active metabolite SN38 in each tissue. Finally, the pharmacodynamic study showed that SN38-PA liposome had higher antitumor effect with the antitumor inhibition rate of 1.61 times than that of CPT-11.

Conclusion

These encouraging data merit further investigation on this novel SN38-PA liposome.