Liposomal nanomedicine for breast cancer therapy

Drug nanocrystals: Surface engineering and its applications in targeted delivery

Drug nanocrystals have received significant attention in drug development due to their enhanced dissolution rate and improved water solubility, making them effective in overcoming issues related to drug hydrophobicity, thereby improving drug bioavailability and treatment effectiveness. Recent advances in preparation techniques have facilitated research on drug surface properties, leading to valuable surface engineering strategies. Surface modification can stabilize drug nanocrystals, making them suitable for versatile drug delivery platforms. Functionalized ligands further enhance the potential for targeted delivery, enabling precision medicine. This review focuses on the surface engineering of drug nanocrystals, discussing various preparation methods, surface ligand design strategies, and their applications in targeted drug delivery, especially for cancer treatments. Finally, challenges and future directions are also discussed to promote the development of drug nanocrystals. The surface engineering of drug nanocrystals promises new opportunities for treating complex and chronic diseases while broadening the application of drug delivery systems.

Formulation and Evaluation of a Transferosomal Gel of Famciclovir for Transdermal Use

Objectives

Famciclovir, the drug of choice for cold sores and recurrent genital herpes, has poor oral bioavailability and is associated with numerous side effects. The study aimed to explore the possibility of transdermal application of famciclovir through a transferosome-loaded gelling system to localize the drug at the site of application with improved penetrability, therapeutic effects, and comfort.

Materials and Methods

Transferosomes of famciclovir were prepared using tween 80, phospholipid, and cholesterol. To optimize drug entrapment and the vesicular size of the transferosomes, a central composite design was employed. The optimized formulation was evaluated for physicochemical characteristics, surface morphology, and degree of deformability. The optimized product was included in the Carbopol 940 gelling system. The gel was evaluated for ex vivo permeation, skin irritation, drug deposition at various skin layers, and histopathological analysis.

Results

The design optimization yielded an optimized product (FAMOPT) of nanosized (339 nm) stable vesicles of the transferosome of famciclovir. The surface morphology analysis revealed the formation of nanovesicles without aggregation. Compatibility between the drug and excipients was established. The elasticity of the vesicles demonstrated resistance to leakage. The permeation of the drug was enhanced by 2.8 times. The gel was found to be non-irritating and non-sensitizing to the animal skin. The drug deposition at various skin layers was remarkably improved, indicating effective drug penetration. The histopathological examination further demonstrated the penetration of nano-vesiculate drugs through deeper layers of the skin.

Conclusion

Hence, nano-vesicular famciclovir delivery is a promising alternative to conventional famciclovir delivery with enhanced local and systemic action for herpes treatment.

QbD Enabled Development and Evaluation of Pazopanib Loaded Nanoliposomes for PDAC Treatment

Pancreatic ductal adenocarcinoma (PDAC) is one of the highly fatal types of cancer with high mortality/incidence. Considering the crucial role of vascular endothelial growth factor (VEGF) in PDAC progression, its inhibition can be a viable strategy for the treatment. Pazopanib, a second-generation VEGF inhibitor, is approved for the treatment of various oncological conditions. However, due to associated limitations like low oral bioavailability (14-39%), high inter/intra-subject variability, stability issues, etc., high doses (800 mg) are required, which further lead to non-specific toxicities and also contribute toward cancer resistance. Thus, to overcome these challenges, pazopanib-loaded PEGylated nanoliposomes were developed and evaluated against pancreatic cancer cell lines. The nanoliposomes were prepared by thin-film hydration method, followed by characterization and stability studies. This QbD-enabled process design successfully led to the development of a suitable pazopanib liposomal formulation with desirable properties. The % entrapment of PZP-loaded non-PEGylated and PEGylated nanoliposomes was found to be 75.2% and 84.9%, respectively, whereas their particle size was found to be 129.7 nm and 182.0 nm, respectively. The developed liposomal formulations exhibited a prolonged release and showed desirable physicochemical properties. Furthermore, these liposomal formulations were also assessed for in vitro cell lines, such as cell cytotoxicity assay and cell uptake. These studies confirm the effectiveness of developed liposomal formulations against pancreatic cancer cell lines. The outcomes of this work provide encouraging results and a way forward to thoroughly investigate its potential for PDAC treatment.

A Journey of Challenges and Victories: A Bibliometric Worldview of Nanomedicine since the 21st Century

Nanotechnology profoundly affects the advancement of medicine. Limitations in diagnosing and treating cancer and chronic diseases promote the growth of nanomedicine. However, there are very few analytical and descriptive studies regarding the trajectory of nanomedicine, key research powers, present research landscape, focal investigative points, and future outlooks. Herein, articles and reviews published in the Science Citation Index Expanded of Web of Science Core Collection from first January 2000 to 18th July 2023 are analyzed. Herein, a bibliometric visualization of publication trends, countries/regions, institutions, journals, research categories, themes, references, and keywords is produced and elaborated. Nanomedicine-related academic output is increasing since the COVID-19 pandemic, solidifying the uneven global distribution of research performance. While China leads in terms of publication quantity and has numerous highly productive institutions, the USA has advantages in academic impact, commercialization, and industrial value. Nanomedicine integrates with other disciplines, establishing interdisciplinary platforms, in which drug delivery and nanoparticles remain focal points. Current research focuses on integrating nanomedicine and cell ferroptosis induction in cancer immunotherapy. The keyword "burst testing" identifies promising research directions, including immunogenic cell death, chemodynamic therapy, tumor microenvironment, immunotherapy, and extracellular vesicles. The prospects, major challenges, and barriers to addressing these directions are discussed.

Therapeutic Delivery of Tumor Suppressor miRNAs for Breast Cancer Treatment

The death rate from breast cancer (BC) has dropped due to early detection and sophisticated therapeutic options, yet drug resistance and relapse remain barriers to effective, systematic treatment. Multiple mechanisms underlying miRNAs appear crucial in practically every aspect of cancer progression, including carcinogenesis, metastasis, and drug resistance, as evidenced by the elucidation of drug resistance. Non-coding RNAs called microRNAs (miRNAs) attach to complementary messenger RNAs and degrade them to inhibit the expression and translation to proteins. Evidence suggests that miRNAs play a vital role in developing numerous diseases, including cancer. They affect genes critical for cellular differentiation, proliferation, apoptosis, and metabolism. Recently studies have demonstrated that miRNAs serve as valuable biomarkers for BC. The contrast in the expression of miRNAs in normal tissue cells and tumors suggest that miRNAs are involved in breast cancer. The important aspect behind cancer etiology is the deregulation of miRNAs that can specifically influence cellular physiology. The main objective of this review is to emphasize the role and therapeutic capacity of tumor suppressor miRNAs in BC and the advancement in the delivery system that can deliver miRNAs specifically to cancerous cells. Various approaches are used to deliver these miRNAs to the cancer cells with the help of carrier molecules, like nanoparticles, poly D, L-lactic-co-glycolic acid (PLGA) particles, PEI polymers, modified extracellular vesicles, dendrimers, and liposomes. Additionally, we discuss advanced strategies of TS miRNA delivery techniques such as viral delivery, self-assembled RNA-triple-helix hydrogel drug delivery systems, and hyaluronic acid/protamine sulfate inter-polyelectrolyte complexes. Subsequently, we discuss challenges and prospects on TS miRNA therapeutic delivery in BC management so that miRNAs will become a routine technique in developing individualized patient profiles.

Receptor-Mediated Targeted Delivery of Surface-ModifiedNanomedicine in Breast Cancer: Recent Update and Challenges

Breast cancer therapeutic intervention continues to be ambiguous owing to the lack of strategies for targeted transport and receptor-mediated uptake of drugs by cancer cells. In addition to this, sporadic tumor microenvironment, prominent restrictions with conventional chemotherapy, and multidrug-resistant mechanisms of breast cancer cells possess a big challenge to even otherwise optimal and efficacious breast cancer treatment strategies. Surface-modified nanomedicines can expedite the cellular uptake and delivery of drug-loaded nanoparticulate constructs through binding with specific receptors overexpressed aberrantly on the tumor cell. The present review elucidates the interesting yet challenging concept of targeted delivery approaches by exploiting different types of nanoparticulate systems with multiple targeting ligands to target overexpressed receptors of breast cancer cells. The therapeutic efficacy of these novel approaches in preclinical models is also comprehensively discussed in this review. It is concluded from critical analysis of related literature that insight into the translational gap between laboratories and clinical settings would provide the possible future directions to plug the loopholes in the process of development of these receptor-targeted nanomedicines for the treatment of breast cancer.

Recent advances in liposome formulations for breast cancer therapeutics

Among many nanoparticle-based delivery platforms, liposomes have been particularly successful with many formulations passed into clinical applications. They are well-established and effective gene and/or drug delivery systems, widely used in cancer therapy including breast cancer. In this review we discuss liposome design with the targeting feature and triggering functions. We also summarise the recent progress (since 2014) in liposome-based therapeutics for breast cancer including chemotherapy and gene therapy. We finally identify some challenges on the liposome technology development for the future clinical translation.

Nanotheranostics for Cancer Therapy and Detection: State of the Art

Nanotheranostics, an approach of combining both diagnosis and therapy, is one of the latest advances in cancer therapy particularly. Nanocarriers designed and derived from inorganic materials such as like gold nanoparticles, silica nanoparticles, magnetic nanoparticles and carbon nanotubes have been explored for tremendous applications in this area. Similarly, nanoparticles composed of some organic material alone or in combination with inorganic nano-cargos have been developed pre-clinically and possess excellent features desired. Photothermal therapy, MRI, simultaneous imaging and delivery, and combination chemotherapy with a diagnosis are a few of the known methods exploring cancer therapy and detection at organ/tissue/molecular/sub-cellular level. This review comprises an overview of the recent reports meant for nano theranostics purposes. Targeted cancer nanotheranostics have been included for understating tumor micro-environment or cell-specific targeting approach employed. A brief account of various strategies is also included for the readers highlighting the mechanism of cancer therapy.

Galactosylated TPGS Micelles for Docetaxel Targeting to Hepatic Carcinoma: Development, Characterization, and Biodistribution Study

Hepatocellular carcinoma (HCC) is a foremost type of cancer problem in which asialoglycoprotein receptors are overexpressed. In this study, asialoglycoprotein receptor-targeted nanoformulation (galactose-conjugated TPGS micelles) loaded with docetaxel (DTX) was developed to achieve its site-specific delivery for HCC therapy. The pharmaceutical characteristics like shape morphology, average particle size and zeta potential, drug entrapment efficiency, and in vitro release kinetics of developed system were evaluated. DTX-loaded galactosylated TPGS (DTX-TPGS-Gal) micelles and TPGS micelles (DTX-TPGS) were having 58.76 ± 1.82% and 54.76 ± 1.42% entrapment of the DTX, respectively. In vitro drug release behavior from micelles was controlled release. Cytotoxicitiy (IC₅₀) of DTX-TPGS-Gal formulation on HepG2 cell lines was significantly (p ≤ 0.01) lower (6.3 ± 0.86 μg/ml) than DTX-TPGS (9.06 ± 0.82 μg/ml) and plain DTX (16.06 ± 0.98 μg/ml) indicating higher efficacy of targeted formulation. Further, in vivo biodistribution studies in animal model showed maximum drug accumulation at target site, i.e., the liver in the case of DTX-TPGS-Gal as compared with non-targeted one. It is concluded from the findings that TPGS-Gal micelles can be utilized for targeted drug delivery of cytotoxic drugs towards HCC with minimized side effects. Graphical abstract.

Liposomal Avicequinone-B formulations: Aqueous solubility, physicochemical properties and apoptotic effects on cutaneous squamous cell carcinoma cells

BACKGROUND

Avicequinone-B (Naphtho[2,3-b]furan-4,9-dione) is a furanonaphthoquinone derivative. It is a hydrophobic compound with poor aqueous solubility, which may restrict its potential pharmaceutical and biomedical applications.

PURPOSE

We synthesized different liposomal formulations of Avicequinone-B, and measured their particle size, aqueous solubility, and physicochemical properties. In addition, we investigated the anticancer activity of liposomal Avicequinone-B in human cutaneous squamous cell carcinoma (SCC) cells.

METHODS

Liposomal Avicequinone-B formulations were synthesized using the thin-film hydration method. Drug yield, encapsulation efficiency and aqueous solubility were determined by high performance liquid chromatography. Particle size and polydispersity index were measured by submicron particle size analyzer, and ultrastructural morphology was visualized by transmission electron microscopy. Thermal transitions were determined by differential scanning calorimetry. Anti-skin cancer activity was determined in HSC-1 cells (human cutaneous SCC cell line) using the MTS cytotoxicity assay, apoptosis was assessed by caspase-3/7 activity assay, mitochondrial membrane potential was determined by JC-10 assay, and signal transduction pathways were evaluated by Western blot analysis.

RESULTS

Liposomal Avicequinone-B formulations showed adequate yield and high encapsulation efficiency. These liposomal formulations produced small, uniformly sized nanoparticles, and greatly increased the aqueous solubility of Avicequinone-B. Differential scanning calorimetry showed loss of thermal phase transitions. In addition, liposomal Avicequinone-B showed significant cytotoxic effect on HSC-1 cells, through reduction of mitochondrial membrane potential, increased cytosolic cytochrome-c level, increased cleaved caspase 8 level, and induction of apoptosis. This was mediated through activation of ERK, p38 and JNK signaling pathways.

CONCLUSION

Liposomal Avicequinone-B demonstrated improved aqueous solubility and physicochemical characteristics, and induced apoptosis in cutaneous SCC cells. Therefore, liposomal Avicequinone-B may have potential uses as a topical anti-skin cancer drug formulation in the future.

Blood Interactions, Pharmacokinetics, and Depth-Dependent Ablation of Rat Mammary Tumors with Photoactivatable, Liposomal Doxorubicin

Photosensitizers can be integrated with drug delivery vehicles to develop chemophototherapy agents with antitumor synergy between chemo- and photocomponents. Long-circulating doxorubicin (Dox) in porphyrin-phospholipid (PoP) liposomes (LC-Dox-PoP) incorporates a phospholipid-like photosensitizer (2 mole %) in the bilayer of Dox-loaded stealth liposomes. Hematological effects of endotoxin-minimized LC-Dox-PoP were characterized via standardized assays. In vitro interaction with erythrocytes, platelets, and plasma coagulation cascade were generally unremarkable, whereas complement activation was found to be similar to that of commercial Doxil. Blood partitioning suggested that both the Dox and PoP components of LC-Dox-PoP were stably entrapped or incorporated in liposomes. This was further confirmed with pharmacokinetic studies in Fischer rats, which showed the PoP and Dox components of the liposomes both had nearly identical, long circulation half-lives (25-26 hours). In a large orthotopic mammary tumor model in Fischer rats, following intravenous dosing (2 mg/kg Dox), the depth of enhanced Dox delivery in response to 665 nm laser irradiation was over 1 cm. LC-Dox-PoP with laser treatment cured or potently suppressed tumor growth, with greater efficacy observed in tumors 0.8 to 1.2 cm, compared with larger ones. The skin at the treatment site healed within approximately 30 days. Taken together, these data provide insight into nanocharacterization and photo-ablation parameters for a chemophototherapy agent.

SN38-loaded <100 nm targeted liposomes for improving poor solubility and minimizing burst release and toxicity: in vitro and in vivo study

Background

SN38 (7-ethyl-10-hydroxycamptothecin) is a camptothecin derivative acts against various tumors. However, SN38 is hydrolyzed in the physiological environment (pH 7.4), and this instability interferes with its potential therapeutic effect. Our objective was to investigate SN38-loaded liposomes to overcome the poor solubility of SN38 and its biodistribution, which further diminish its toxicity.

Materials and methods

The sub-100 nm targeted liposomes was employed to deliver SN-38 and evaluate the characterization, release behaviors, cytotoxicity, in vivo pharmacokinetics and biochemical assay.

Results

The SN38-loaded targeted liposomes consisted of small (100.49 nm) spherical nanoparticles with negative charge (−37.93 mV) and high entrapment efficiency (92.47%). The release behavior of the SN38-loaded targeted liposomes was fitted with Higuchi kinetics (R²=0.9860). Free SN38 presented initial burst release. The IC₅₀ for the SN38-loaded targeted liposomes (0.11 μM) was significantly lower than for the SN38 solution (0.37 μM) in the MCF7 cell line (P<0.01). Confocal laser scanning microscopy also confirmed highly efficient accumulation in the MCF7 cells. Pharmacokinetics demonstrated that the SN38-loaded targeted liposomes had a slightly increased half-life and mean residence time and decreased area under the concentration–time curve and maximum concentration. The results suggested that retention was achieved while the exposure of SN38 was significantly decreased. A noninvasive in vivo imaging system also showed that the targeted liposomes selectively targeted MCF7 tumors. In vivo toxicity data demonstrated that the decrease in platelets was significantly improved by SN38-loaded targeted liposomes, and diarrhea was not observed in BALB/c mice.

Conclusion

In summary, SN38-loaded targeted liposomes could be a good candidate for application in human breast cancer.

Elasto-electro-capillarity: drop equilibrium on a charged, elastic solid

We present a study here on elasto-electro-capillarity - for the first time, the matter of drop equilibrium on a soft (elastic and incompressible) and charged solid has been studied. Charges on the elastic solid induce an electric double layer or EDL at the solid-drop interface. Our analysis accounts for the electrostatic wetting contribution of the EDL in the overall energy balance. Our results reveal that (a) with an increase in "softness", the equilibrium solid-liquid contact angles show transition from the EDL-modified Young's law (rigid limit) to the EDL-modified Neumann's law (soft limit); (b) the EDL effects invariably enhance solid deformation and lower the apparent contact angle made by the drop with the undeformed solid; (c) the solid contact angles increase and the cusp made by the deformed solid undergoes enhanced rotation due to the EDL effects; and (d) the EDL effects are more prominent for the case where the solid-vapor surface energy exceeds the solid-liquid surface energy. The fact that the EDL effects invariably decrease the overall wetting energy of the system, thereby supporting a larger increase in the elastic energy associated with a larger solid deformation, explains all these findings and establishes that surface charges enhance the "softness" of a soft surface in the context of elastocapillarity.

Preparation and Characterization of Lipophilic Doxorubicin Pro-drug Micelles

Micelles have been successfully used for the delivery of anticancer drugs. Amphiphilic polymers form core-shell structured micelles in an aqueous environment through self-assembly. The hydrophobic core of micelles functions as a drug reservoir and encapsulates hydrophobic drugs. The hydrophilic shell prevents the aggregation of micelles and also prolongs their systemic circulation in vivo. In this protocol, we describe a method to synthesize a doxorubicin lipophilic pro-drug, doxorubicin-palmitic acid (DOX-PA), which will enhance drug loading into micelles. A pH-sensitive hydrazone linker was used to conjugate doxorubicin with the lipid, which facilitates the release of free doxorubicin inside cancer cells. Synthesized DOX-PA was purified with a silica gel column using dichloromethane/methanol as the eluent. Purified DOX-PA was analyzed with thin layer chromatography (TLC) and (1)H-Nuclear Magnetic Resonance Spectroscopy ((1)H-NMR). A film dispersion method was used to prepare DOX-PA loaded DSPE-PEG micelles. In addition, several methods for characterizing micelle formulations are described, including determination of DOX-PA concentration and encapsulation efficiency, measurement of particle size and distribution, and assessment of in vitro anticancer activities. This protocol provides useful information regarding the preparation and characterization of drug-loaded micelles and thus will facilitate the research and development of novel micelle-based cancer nanomedicines.

Targeted Ultrasound-Assisted Cancer-Selective Chemical Labeling and Subsequent Cancer Imaging using Click Chemistry

Metabolic sugar labeling followed by the use of reagent-free click chemistry is an established technique for in vitro cell targeting. However, selective metabolic labeling of the target tissues in vivo remains a challenge to overcome, which has prohibited the use of this technique for targeted in vivo applications. Herein, we report the use of targeted ultrasound pulses to induce the release of tetraacetyl N-azidoacetylmannosamine (Ac4 ManAz) from microbubbles (MBs) and its metabolic expression in the cancer area. Ac4 ManAz-loaded MBs showed great stability under physiological conditions, but rapidly collapsed in the presence of tumor-localized ultrasound pulses. The released Ac4 ManAz from MBs was able to label 4T1 tumor cells with azido groups and significantly improved the tumor accumulation of dibenzocyclooctyne (DBCO)-Cy5 by subsequent click chemistry. We demonstrated for the first time that Ac4 ManAz-loaded MBs coupled with the use of targeted ultrasound could be a simple but powerful tool for in vivo cancer-selective labeling and targeted cancer therapies.

Novel therapeutic approaches for pulmonary arterial hypertension: Unique molecular targets to site-specific drug delivery

Pulmonary arterial hypertension (PAH) is a cardiopulmonary disorder characterized by increased blood pressure in the small arterioles supplying blood to lungs for oxygenation. Advances in understanding of molecular and cellular biology techniques have led to the findings that PAH is indeed a cascade of diseases exploiting multi-faceted complex pathophysiology, with cellular proliferation and vascular remodeling being the key pathogenic events along with several cellular pathways involved. While current therapies for PAH do provide for amelioration of disease symptoms and acute survival benefits, their full therapeutic potential is hindered by patient incompliance and off-target side effects. To overcome the issues related with current therapy and to devise a more selective therapy, various novel pathways are being investigated for PAH treatment. In addition, inability to deliver anti-PAH drugs to the disease site i.e., distal pulmonary arterioles has been one of the major challenges in achieving improved patient outcomes and improved therapeutic efficacy. Several novel carriers have been explored to increase the selectivity of currently approved anti-PAH drugs and to act as suitable carriers for the delivery of investigational drugs. In the present review, we have discussed potential of various novel molecular pathways/targets including RhoA/Rho kinase, tyrosine kinase, endothelial progenitor cells, vasoactive intestinal peptide, and miRNA in PAH therapeutics. We have also discussed various techniques for site-specific drug delivery of anti-PAH therapeutics so as to improve the efficacy of approved and investigational drugs. This review will provide gainful insights into current advances in PAH therapeutics with an emphasis on site-specific drug payload delivery.

Multifunctional iron bound lactoferrin and nanomedicinal approaches to enhance its bioactive functions

Lactoferrin (Lf), an iron-binding protein from the transferrin family has been reported to have numerous functions. Even though Lf was first isolated from milk, it is also found in most exocrine secretions and in the secondary granules of neutrophils. Antimicrobial and anti-inflammatory activity reports on lactoferrin identified its significance in host defense against infection and extreme inflammation. Anticarcinogenic reports on lactoferrin make this protein even more valuable. This review is focused on the structural configuration of iron-containing and iron-free forms of lactoferrin obtained from different sources such as goat, camel and bovine. Apart for emphasizing on the specific beneficial properties of lactoferrin from each of these sources, the general antimicrobial, immunomodulatory and anticancer activities of lactoferrin are discussed here. Implementation of nanomedicinial strategies that enhance the bioactive function of lactoferrin are also discussed, along with information on lactoferrin in clinical trials.

Theranostic lipid nanoparticles for cancer medicine

Disease heterogeneity within and between patients necessitates a patient-focused approach to cancer treatment. This exigency forms the basis for the medical practice termed personalized medicine. An emerging, important component of personalized medicine is theranostics. Theranostics describes the co-delivery of therapeutic and imaging agents in a single formulation. Co-delivery enables noninvasive, real-time visualization of drug fate, including drug pharmacokinetic and biodistribution profiles and intratumoral accumulation. These technological advances assist drug development and ultimately may translate to improved treatment planning at the bedside. Nanocarriers are advantageous for theranostics as their size and versatility enables integration of multiple functional components in a single platform. This chapter focuses on recent developments in advanced lipid theranostic nanomedicine from the perspective of the "all-in-one" or the "one-for-all" approach. The design paradigm of "all-in-one" is the most common approach for assembling theranostic lipid nanoparticles, where the advantages of theranostics are achieved by combining multiple components that each possesses a specific singular function for therapeutic activity or imaging contrast. We will review lipoprotein nanoparticles and liposomes as representatives of the "all-in-one" approach. Complementary to the "all-in-one" approach is the emerging paradigm of the "one-for-all" approach where nanoparticle components are intrinsically multifunctional. We will discuss the "one-for-all" approach using porphysomes as a representative. We will further discuss how the concept of "one-for-all" might overcome the regulatory hurdles facing theranostic lipid nanomedicine.

Short-chain glycoceramides promote intracellular mitoxantrone delivery from novel nanoliposomes into breast cancer cells

PURPOSE

To improve therapeutic activity of mitoxantrone (MTO)-based chemotherapy by reducing toxicity through encapsulation in nanoliposomes and enhancing intracellular drug delivery using short-chain sphingolipid (SCS) mediated tumor cell membrane permeabilization.

METHODS

Standard (MTOL) and nanoliposomes enriched with the SCS, C8-Glucosylceramide or C8-Galactosylceramide (SCS-MTOL) were loaded by a transmembrane ammonium sulphate gradient and characterized by DLS and cryo-TEM. Intracellular MTO delivery was measured by flow cytometry and imaged by fluorescence microscopy. In vitro cytotoxicity was studied in breast carcinoma cell lines. Additionally, live cell confocal microscopy addressed the drug delivery mechanism by following the intracellular fate of the nanoliposomes, the SCS and MTO. Intratumoral MTO localization in relation to CD31-positive tumor vessels and CD11b positive cells was studied in an orthotopic MCF-7 breast cancer xenograft.

RESULTS

Stable SCS-MTOL were developed increasing MTO delivery and cytotoxicity to tumor cells compared to standard MTOL. This effect was much less pronounced in normal cells. The drug delivery mechanism involved a transfer of SCS to the cell membrane, independently of drug transfer and not involving nanoliposome internalization. MTO was detected intratumorally upon MTOL and SCS-MTOL treatment, but not after free MTO, suggesting an important improvement in tumor drug delivery by nanoliposomal formulation. Nanoliposomal MTO delivery and cellular uptake was heterogeneous throughout the tumor and clearly correlated with CD31-positive tumor vessels. Yet, MTO uptake by CD11b positive cells in tumor stroma was minor.

CONCLUSIONS

Nanoliposomal encapsulation improves intratumoral MTO delivery over free drug. Liposome bilayer-incorporated SCS preferentially permeabilize tumor cell membranes enhancing intracellular MTO delivery.

A review of mechanistic insight and application of pH-sensitive liposomes in drug delivery

The pH-sensitive liposomes have been extensively used as an alternative to conventional liposomes in effective intracellular delivery of therapeutics/antigen/DNA/diagnostics to various compartments of the target cell. Such liposomes are destabilized under acidic conditions of the endocytotic pathway as they usually contain pH-sensitive lipid components. Therefore, the encapsulated content is delivered into the intracellular bio-environment through destabilization or its fusion with the endosomal membrane. The therapeutic efficacy of pH-sensitive liposomes enables them as biomaterial with commercial utility especially in cancer treatment. In addition, targeting ligands including antibodies can be anchored on the surface of pH-sensitive liposomes to target specific cell surface receptors/antigen present on tumor cells. These vesicles have also been widely explored for antigen delivery and serve as immunological adjuvant to enhance the immune response to antigens. The present review deals with recent research updates on application of pH-sensitive liposomes in chemotherapy/diagnostics/antigen/gene delivery etc.

pH-sensitive Liposomes in Drug Delivery

The pH-sensitive liposomes have been extensively studied in recent years as an advantageous alternative to conventional liposomes in effective targeting and accumulation of anticancer drugs in tumors. pH-sensitive liposomes usually contain phosphatidylethanolamine and stabilizing amphiphiles and can destabilize under acidic conditions of the endocytotic pathway. The drug loaded is thought to be delivered into the cytoplasm, probably through destabilization of or fusion with the endosome membrane. This fusogenic property makes the pH-sensitive liposomes more efficient in delivering anticancer drugs than conventional liposomes. The intra-cellular release of drug/gene/diagnostic agents can be achieved without altering their therapeutic efficacy by means of the endosomal escape phenomenon. Cell surface targeting ligands, including antibodies, can be appended on the surface of pH-sensitive liposomes to target specific receptors on tumor cells. This chapter provides an introduction to pH-sensitive liposomes and examples of their therapeutic interest as smart drug-delivery systems.

Abrogation of the accelerated blood clearance phenomenon by SOXL regimen: promise for clinical application

We recently proposed an S-1 combined with oxaliplatin (SOXL) regimen, a combination treatment consisting of oral metronomic S-1 dosing and intravenous administration of oxaliplatin (l-OHP) containing PEGylated liposomes, which showed potent antitumor activity in vivo. PEGylated liposomes induce what is referred to as the "accelerated blood clearance (ABC) phenomenon" upon repeated administration and consequently lose their long-circulating characteristics. This phenomenon seems to pose an impediment for the clinical application and use of PEGylated liposomal formulations. In the present study, l-OHP-containing PEGylated liposomes in the SOXL regimen significantly attenuated the ABC phenomenon in a dose-dependent manner through suppression of the anti-PEG IgM response, which allowed an enhanced hepatic uptake of subsequently injected test PEGylated liposomes. In tumor-bearing mice, the abrogation of the ABC phenomenon restored intratumor accumulation of subsequently injected PEGylated liposomes. Consequently, the therapeutic efficacy of the SOXL regimen over the combination of the free form of the drugs was credited not only with the selective delivery of drugs to the tumor tissue but also with ensuring an adequate accumulation of subsequent doses within the tumor tissue. The SOXL regimen we proposed may hold promise as a safe and effective treatment regimen for advanced colorectal cancer.