Development and characterization of a novel liposome-based formulation of SN-38

Synthesis and Biological Evaluation of Methoxypolyethylene-Glycol-Substituted Abiraterone Derivatives as Potential Antiprostate Cancer Agents

Globally, prostate cancer is the most commonly diagnosed tumor and a cause of death in older men. Abiraterone, an orally administered irreversible CYP17 inhibitor, is employed to treat prostate cancer. However, abiraterone has several clinical limitations, such as poor water solubility, low dissolution rate, low bioavailability, and toxic side effects in the liver and kidney. Therefore, there is a need to identify high-efficiency and low-toxicity water-soluble abiraterone derivatives. In this work, we aimed to design and synthesize a series of abiraterone derivatives by methoxypoly(ethylene glycol) (mPEG) modification. Their antitumor activities and toxicology were analyzed in vitro and in vivo. The most potent compound, 2e, retained the principle of action on the CYP17 enzyme target and significantly improved the abiraterone water solubility, cell permeability, and blood safety. No significant abnormalities were observed in toxicology. mPEG-modification significantly improved abiraterone's antitumor activity and efficiency while reducing the associated toxic effects. The finding will provide a theoretical basis for future clinical application of mPEG-modified abiraterone.

Unleashing the Potential of Camptothecin: Exploring Innovative Strategies for Structural Modification and Therapeutic Advancements

Camptothecin (CPT) is a potent anti-cancer agent targeting topoisomerase I (TOP1). However, CPT has poor pharmacokinetic properties, causes toxicities, and leads to drug resistance, which limit its clinical use. In this paper, to review the current state of CPT research. We first briefly explain CPT's TOP1 inhibition mechanism and the key hurdles in CPT drug development. Then we examine strategies to overcome CPT's limitations through structural modifications and advanced delivery systems. Though modifications alone seem insufficient to fully enhance CPT's therapeutic potential, structure-activity relationship analysis provides insights to guide optimization of CPT analogs. In comparison, advanced delivery systems integrating controlled release, imaging capabilities, and combination therapies via stimulus-responsive linkers and targeting moieties show great promise for improving CPT's pharmacological profile. Looking forward, multifaceted approaches combining selective CPT derivatives with advanced delivery systems, informed by emerging biological insights, hold promise for fully unleashing CPT's anti-cancer potential.

SN38-loaded nanomedicine mediates chemo-radiotherapy against CD44-expressing cancer growth

Background

Chemo-radiotherapy is the combined chemotherapy and radiotherapy on tumor treatment to obtain the local radiosensitization and local cytotoxicity of the tumor and to control the microscopic metastatic disease.

Methods

In this study, 7-ethyl-10-hydroxycamptothecin (SN38) molecules could be successfully loaded into human serum albumin (HSA)–hyaluronic acid (HA) nanoparticles (SH/HA NPs) by the hydrophobic side groups of amino acid in HSA.

Results

HSA could be used to increase the biocompatibility and residence time of the nanoparticles in the blood, whereas HA could improve the benefits and overall treatment effect on CD44-expressing colorectal cancer (CRC), and reduce drug side effects. In addition to its role as a chemotherapeutic agent, SN38 could be used as a radiosensitizer, able to arrest the cell cycle, and allowing cells to stay in the G2/M stage, to improve the sensitivity of tumor cells to radiation. In vivo results demonstrated that SH/HA NPs could accumulate in the tumor and produce significant tumor suppression, with no adverse effects observed when combined with γ-ray irradiation. This SH/HA NPs-medicated chemo-radiotherapy could induce an anti-tumor immune response to inhibit the growth of distal tumors, and produce an abscopal effect.

Conclusions

Therefore, this SN38-loaded and HA-incorporated nanoparticle combined with radiotherapy may be a promising therapeutic artifice for CRC in the future.

Engineered Liposomes in Interventional Theranostics of Solid Tumors

Engineered liposomal nanoparticles have unique characteristics as cargo carriers in cancer care and therapeutics. Liposomal theranostics have shown significant progress in preclinical and clinical cancer models in the past few years. Liposomal hybrid systems have not only been approved by the FDA but have also reached the market level. Nanosized liposomes are clinically proven systems for delivering multiple therapeutic as well as imaging agents to the target sites in (i) cancer theranostics of solid tumors, (ii) image-guided therapeutics, and (iii) combination therapeutic applications. The choice of diagnostics and therapeutics can intervene in the theranostics property of the engineered system. However, integrating imaging and therapeutics probes within lipid self-assembly "liposome" may compromise their overall theranostics performance. On the other hand, liposomal systems suffer from their fragile nature, site-selective tumor targeting, specific biodistribution and premature leakage of loaded cargo molecules before reaching the target site. Various engineering approaches, viz., grafting, conjugation, encapsulations, etc., have been investigated to overcome the aforementioned issues. It has been studied that surface-engineered liposomes demonstrate better tumor selectivity and improved therapeutic activity and retention in cells/or solid tumors. It should be noted that several other parameters like reproducibility, stability, smooth circulation, toxicity of vital organs, patient compliance, etc. must be addressed before using liposomal theranostics agents in solid tumors or clinical models. Herein, we have reviewed the importance and challenges of liposomal medicines in targeted cancer theranostics with their preclinical and clinical progress and a translational overview.

A ROS-response hyaluronic acid-coated/chitosan polymer prodrug for enhanced tumor targeting efficacy of SN38

Ethyl-10-hydroxycamptothecin (SN38) is a camptothecin derivative with significant anti-tumor therapeutic potential, while the clinical application of SN38 was limited by its poor water solubility and low stability. Herein, a core-shell polymer prodrug hyaluronic acid @chitosan-S-SN38 (HA@CS-S-SN38) was designed by CS-S-SN38 as the core and the HA as the shell, which aims to overcome the limitations of the clinical application of SN38, while realizing the high tumor targeting of polymer prodrug and the controllable release of drug in tumor cells. HA@CS-S-SN38 showed the high responsiveness of the tumor microenvironment and the safe stability of blood circulation. Furthermore, HA@CS-S-SN38 exhibited the begin uptake efficiency and favorable apoptosis in the 4T1 cells. More importantly, compared with irinotecan hydrochloride trihydrate (CPT-11), HA@CS-S-SN38 significantly improved the conversion efficiency of the prodrug to SN38, and showed excellent tumor targeting and retention in vivo by combining passive and active targeting strategies. In tumor-bearing mice treatment, HA@CS-S-SN38 showed the perfect anti-tumor effect and therapeutic safety. These results indicated that the polymer prodrug designed by ROS-response/HA-modification strategy is a safe and efficient drug delivery system, which provides a new idea for clinical utilization of SN38 and warrants further evaluation.

Recent advances in SN-38 drug delivery system

DNA topoisomerase I plays a key role in lubricatingthe wheels of DNA replication or RNA transcription through breaking and reconnecting DNA single-strand. It is widely known that camptothecin and its derivatives (CPTs) have inhibitory effects on topoisomerases I, and have obtained some clinical benefits in cancer treatment. The potent cytotoxicity makes 7-ethyl-10-hydroxycamptothecin (SN-38) become a brilliant star among these derivatives. However, some undesirable physical and chemical properties of this compound, including poor solubility and stability, seriously hinder its effective delivery to tumor sites. In recent years, strategies to alleviate these defects have aroused extensive research interest. By focusing on the loading mechanism, basic nanodrug delivery systems with SN-38 loaded, like nanoparticles, liposomes and micelles, are demonstrated here. Additionally, functionalized nanodrug delivery systems of SN-38 including prodrug and active targeted nanodrug delivery systems and delivery systems designed to overcome drug resistance are also reviewed. At last, challenges for future research in formulation development and clinical translation of SN-38 drug delivery system are discussed.

Insights into the Degradation of Polymer-Drug Conjugates by an Overexpressed Enzyme in Cancer Cells

Intensive efforts have been made to provide better treatments to cancer patients. Currently, nanoparticle-based drug delivery systems have gained propulsion, as they can overcome the drawbacks of free drugs. However, drug stability inside the nanocapsule must be ensured to prevent burst release. To overcome this, drugs conjugated to amphiphilic copolymers, assembled into nanoparticles, can provide a sustained release if endogenously degraded. Thus, we have designed and assessed the drug release viability of polymer-drug conjugates by the human Carboxylesterase 2, for a targeted drug activation. We performed molecular dynamics simulations applying a quantum mechanics/molecular mechanics potential to study the degradation profiles of 30 designed conjugates, where six were predicted to be hydrolyzed by this enzyme. We further analyzed the enzyme-substrate environment to delve into what structural features may lead to successful hydrolysis. These findings contribute to the development of new medicines ensuring effective cancer treatments with fewer side effects.

Targeting efficacy and anticancer activity of polymeric nanoparticles of SN-38 on colon cancer cell lines

Background

Colorectal cancer is the third most prevailing cancer in the whole world. Chemotherapeutic agents which are used for treatment have severe side effects and also have unwanted exposure to healthy cells. In the present study, polymeric nanoparticles of SN-38 were prepared (using cationic and anionic polymers). They were optimized by Box Behnken design and characterized for its physicochemical properties and in vitro drug release. Optimized formulation (CsENP) was evaluated for its targeting efficacy by Gamma Scintigraphy studies on Swiss Albino mice and in vitro Cytotoxic assay against colon cancer cell line, viz. HT-29.

Results

The images of Whole body gamma scintigraphy imaging of Swiss Albino mice show that CsENP remained intact till 2 h and after that at 4 h imaging it started dispersing and releasing drug which continued till 20 h. In Organ distribution studies, no radioactivity was traced in heart from the formulation. Even in liver, spleen, kidney and lung trace radioactivity was seen after 6 h. In case of CsENP radioactivity was seen in small intestine after 2 h and maximum (87.8% radioactivity) is seen in colon and rectum area after 4 h. At equivalent concentrations, the in vitro cell viability of HT-29 cells after 72 h incubation time showed that CsENP have enhanced cytotoxicity.

Conclusions

The results obtained of Whole body gamma scintigraphy imaging and organ distribution of Swiss Albino mice show that CsENP is Colon targeting and was found to be effective against colon cancer cell lines.

Advances in Lung Cancer Treatment Using Nanomedicines

Carcinoma of the lungs is among the most menacing forms of malignancy and has a poor prognosis, with a low overall survival rate due to delayed detection and ineffectiveness of conventional therapy. Therefore, drug delivery strategies that may overcome undesired damage to healthy cells, boost therapeutic efficacy, and act as imaging tools are currently gaining much attention. Advances in material science have resulted in unique nanoscale-based theranostic agents, which provide renewed hope for patients suffering from lung cancer. Nanotechnology has vastly modified and upgraded the existing techniques, focusing primarily on increasing bioavailability and stability of anti-cancer drugs. Nanocarrier-based imaging systems as theranostic tools in the treatment of lung carcinoma have proven to possess considerable benefits, such as early detection and targeted therapeutic delivery for effectively treating lung cancer. Several variants of nano-drug delivery agents have been successfully studied for therapeutic applications, such as liposomes, dendrimers, polymeric nanoparticles, nanoemulsions, carbon nanotubes, gold nanoparticles, magnetic nanoparticles, solid lipid nanoparticles, hydrogels, and micelles. In this Review, we present a comprehensive outline on the various types of overexpressed receptors in lung cancer, as well as the various targeting approaches of nanoparticles.

The Advancement of Biodegradable Polyesters as Delivery Systems for Camptothecin and Its Analogues-A Status Report

Camptothecin (CPT) has demonstrated antitumor activity in lung, ovarian, breast, pancreas, and stomach cancers. However, this drug, like many other potent anticancer agents, is extremely water-insoluble. Furthermore, pharmacology studies have revealed that prolonged schedules must be administered continuously. For these reasons, several of its water-soluble analogues, prodrugs, and macromolecular conjugates have been synthesized, and various formulation approaches have been investigated. Biodegradable polyesters have gained popularity in cancer treatment in recent years. A number of biodegradable polymeric drug delivery systems (DDSs), designed for localized and systemic administration of therapeutic agents, as well as tumor-targeting macromolecules, have entered clinical trials, demonstrating the importance of biodegradable polyesters in cancer therapy. Biodegradable polyester-based DDSs have the potential to deliver the payload to the target while also increasing drug availability at intended site. The systemic toxicity and serious side-effects associated with conventional cancer therapies can be significantly reduced with targeted polymeric systems. This review elaborates on the use of biodegradable polyesters in the delivery of CPT and its analogues. The design of various DDSs based on biodegradable polyesters has been described, with the drug either adsorbed on the polymer's surface or encapsulated within its macrostructure, as well as those in which a hydrolyzed chemical bond is formed between the active substance and the polymer chain. The data related to the type of DDSs, the kind of linkage, and the details of in vitro and in vivo studies are included.

Two-Stage SN38 Release from a Core-Shell Nanoparticle Enhances Tumor Deposition and Antitumor Efficacy for Synergistic Combination with Immune Checkpoint Blockade

Long-circulating nanomedicines efficiently deliver chemotherapies to tumors to reduce general toxicity. However, extended blood circulation of nanomedicines can increase drug exposure to leukocytes and lead to hematological toxicity. Here, we report a two-stage release strategy to enhance the drug deposition and antitumor efficacy of OxPt/SN38 core-shell nanoparticles with a hydrophilic oxaliplatin (OxPt) prodrug coordination polymer core and a lipid shell containing a hydrophobic cholesterol-conjugated SN38 prodrug (Chol-SN38). By conjugating cholesterol to the phenol group of SN38 via an acetal linkage and protecting the 20-hydroxy position with a trimethylsilyl (TMS) group, Chol-SN38 releases SN38 in two stages via esterase-catalyzed cleavage of the acetal linkage in the liver followed by acid-mediated hydrolysis of the TMS group to preferentially release SN38 in tumors. Compared to irinotecan, OxPt/SN38 reduces SN38 blood exposure by 9.0 times and increases SN38 tumor exposure by 4.7 times. As a result, OxPt/SN38 inhibits tumor growth on subcutaneous, spontaneous, and metastatic tumor models by causing apoptotic and immunogenic cell death. OxPt/SN38 exhibits strong synergy with the immune checkpoint blockade to regress subcutaneous colorectal and pancreatic tumors with 33-50% cure rates and greatly inhibits tumor growth and invasion in a spontaneous prostate cancer model and a liver metastasis model of colorectal cancer without causing side effects. Mechanistic studies revealed important roles of enhanced immunogenic cell death and upregulated PD-L1 expression by OxPt/SN38 in activating the tumor immune microenvironment to elicit potent antitumor immunity. This work highlights the potential of combining innovative prodrug design and nanomedicine formulation to address unmet needs in cancer therapy.

Discovery of highly potent and selective 7-ethyl-10-hydroxycamptothecin-glucose conjugates as potential anti-colorectal cancer agents

7-Ethyl-10-hydroxycamptothecin (SN38), a highly potent metabolite of irinotecan, has an anticancer efficacy 100-1000 folds more than irinotecan in vitro. However, the clinical application of SN38 has been limited due to the very narrow therapeutic window and poor water solubility. Herein, we report the SN38-glucose conjugates (Glu-SN38) that can target cancer cells due to their selective uptake via glucose transporters, which are overexpressed in most cancers. The in vitro antiproliferative activities against human cancer cell lines and normal cells of Glu-SN38 were investigated. One of the conjugates named 5b showed high potency and selectivity against human colorectal cancer cell line HCT116. Furthermore, 5b remarkably inhibited the growth of HCT116 in vivo. These results suggested that 5b could be a promising drug candidate for treating colorectal cancer.

Liposome Formulation for Tumor-Targeted Drug Delivery Using Radiation Therapy

Targeted delivery of drugs or other therapeutic agents through internal or external triggers has been used to control and accelerate the release from liposomal carriers in a number of studies, but relatively few utilize energy of therapeutic X-rays as a trigger. We have synthesized liposomes that are triggered by ionizing radiation (RTLs) to release their therapeutic payload. These liposomes are composed of natural egg phosphatidylethanolamine (PE), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol, and 1,2-disteroyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol)-2000] (DSPE-PEG-2000), and the mean size of the RTL was in the range of 114 to 133 nm, as measured by nanoparticle tracking analysis (NTA). The trigger mechanism is the organic halogen, chloral hydrate, which is known to generate free protons upon exposure to ionizing radiation. Once protons are liberated, a drop in internal pH of the liposome promotes destabilization of the lipid bilayer and escape of the liposomal contents. In proof of principle studies, we assessed RTL radiation-release of fluorescent tracers upon exposure to a low pH extracellular environment or exposure to X-ray irradiation. Biodistribution imaging before and after irradiation demonstrated a preferential uptake and release of the liposomes and their cargo at the site of local tumor irradiation. Finally, a potent metabolite of the commonly used chemotherapy irinotecan, SN-38, was loaded into RTL along with near infrared (NIR) fluorescent dyes for imaging studies and measuring tumor cell cytotoxicity alone or combined with radiation exposure, in vitro and in vivo. Fully loaded RTLs were found to increase tumor cell killing with radiation in vitro and enhance tumor growth delay in vivo after three IV injections combined with three, 5 Gy local tumor radiation exposures compared to either treatment modality alone.

Pulmonary delivery of liposomes co-loaded with SN38 prodrug and curcumin for the treatment of lung cancer

A co-delivery system of SN38 (7-ethyl-10-hydroxyl camptothecin) prodrug and CUR (curcumin) was designed for the treatment of lung cancer by pulmonary delivery. SN38 was linked to cell-penetrating peptide (CPP) TAT via a polyethylene glycol (PEG) linker to form the SN38 prodrug (TAT-PEG-SN38). Liposomes co-loaded with amphiphilic TAT-PEG-SN38 and curcumin (Lip-TAT-PEG-SN38/CUR) were successfully prepared by a microfluidic method for the treatment of lung cancer via pulmonary delivery. Lip-TAT-PEG-SN38/CUR showed nanometer-sized sphericity and a particle size of 171.21 nm. Besides, Lip-TAT-PEG-SN38/CUR exhibited enhanced antiproliferative effect, increased cell apoptosis induction and improved cell cycle arrest compared to the single agents in vitro. The combination induced significant tumor inhibition in a BALB/c mouse lung cancer model. These results indicated that our SN38 prodrug and curcumin co-delivery system was a promising candidate for lung cancer treatment.

The synergistic effect of chemo-photothermal therapies in SN-38-loaded gold-nanoshell-based colorectal cancer treatment

Aim: 7-Ethyl-10-hydroxycamptothecin (SN-38)-loaded gold nanoshells nanoparticles (HSP@Au NPs) were developed for combined chemo-photothermal therapy to treat colorectal cancer. Materials & methods: SN-38-loaded nanoparticles (HSP NPs) were prepared by the lyophilization-hydration method, and then developed into gold nanoshells. The nanoparticles were characterized and assessed for photothermal properties, cytotoxicity and hemocompatibility in vitro. In vivo anticancer activity was tested in a tumor mouse model. Results: The HSP@Au NPs (diameter 186.9 nm, zeta potential 33.4 mV) led to significant cytotoxicity in cancer cells exposed to a near-infrared laser. Moreover, the HSP@Au NP-mediated chemo-photothermal therapy displayed significant tumor growth suppression and disappearance (25% of tumor clearance rate) without adverse side effects in vivo. Conclusion: HSP@Au NPs may be promising in the treatment of colorectal cancer in the future.

A modular ROS-responsive platform co-delivered by 10-hydroxycamptothecin and dexamethasone for cancer treatment

Traditional and single treatment strategies are difficult to achieve good results due to tumor resistance and complex mechanisms. Combination therapy through co-delivery systems is one of the methods to improve the effectiveness of cancer treatment. The polyprodrug platform has inherent advantages such as high drug loading and strong stability. Herein, a new reactive oxygen species (ROS)-responsive micelle composed of poly 10-hydroxycamptothecin (pHCPT) and PEG is reported, which loaded dexamethasone (DEX) as synergistic drugs. The micelles collapse in the complex microenvironment of tumor cells to release DEX. The first released DEX can increase the ROS level of tumor cells, thereby facilitating the cleavage of thioketal bonds to release intact HCPT molecules. Meanwhile, DEX can normalize tumor blood vessels, reduce adverse reactions, and further improve the efficacy of HCPT. This co-delivery system shows an ideal tumor suppressive effect in vivo and in vitro. Designing drugs into a modular multi-drug platform and selecting appropriate synergistic drugs according to the treatment plan provides a convenient strategy for future clinical treatment.

A tumor microenvironment responsive nanosystem for chemodynamic/chemical synergistic theranostics of colorectal cancer

Rationale: The synergism of new modalities alongside chemodynamic therapy into common chemotherapy has shown promising potential in clinical applications. This paper reports a tumor microenvironment-responsive nanosystem for chemodynamic/chemical synergistic therapy and magnetic resonance imaging (MRI). Methods: The biodegradable nanosystem is synthesized using a surface-modified chain transfer agent for surface-initiated living radical polymerization of the chemotherapeutic drug. Results: In this nanosystem, named CAMNSN@PSN38, the cycling time and solubility of the chemotherapeutic drug are improved. The nanoparticles delivered to tumor tissues gradually release the chemotherapeutic drug and Mn2+ through glutathione (GSH)-triggered biodegradation in the tumor microenvironment. SN38, the released chemotherapeutic drug, not only shows excellent chemical therapy effects but also improves the generation of H2O2. Furthermore, with the Fenton-like agent Mn2+, the generation of reactive oxygen species (ROS) is improved markedly. Finally, CAMNSN@PSN38 shows excellent inhibition of tumor growth in three colorectal cancer tumor models, with an improved accumulation of ROS and controlled release of SN38. Conclusions: The CAMNSN@PSN38-mediated chemodynamic/chemical synergistic therapy provides a promising paradigm for the treatment and MRI-guided therapy of colorectal cancer.

Redox-sensitive irinotecan liposomes with active ultra-high loading and enhanced intracellular drug release

In this report, a novel irinotecan (IR) encapsulated redox-responsive liposome was developed. The redox-responsive liposomes were prepared based on disulfide phosphatidylcholine (SS-PC), DSPC, DSPE-PEG2000 and cholesterol by ethanol injection method. IR was actively loaded by triethylammonium sucrose octasulfate (TEA8-SOS) gradient method to generate IR/SS-PC liposomes (IR/SS-LP). The particle size of IR/SS-PC was characterized by using dynamic light scattering (DLS) and transmission electron microscopy (TEM). It was found that IR/SS-LP with 30 % content of SS-PC (IR/SS30-LP) had an average size of 125.5 ± 5.8 nm with a negative zeta potential of -19.5 ± 0.1. The encapsulation efficiency (EE) was further determined to be 98.1 ± 0.8 % and drug loading (DL) was 31.8 ± 0.1 %. The redox-responsiveness of IR/SS-LP was investigated by observing the change of particle size and morphology as well as the release behavior of IR triggered by glutathione (GSH). The data indicated GSH breaks the disulfide bonds in SS-PC and leads to the controlled release of IR. At 1 mM GSH, 60.2 % irinotecan was released from IR/SS30-LP within 24 h. Finally, the effects of IR/SS-LP in cell and animal experiments were evaluated in detail. The results showed that IR/SS30-LP had superior pharmacokinetic and antitumor efficacy compared to free irinotecan and traditional irinotecan liposome (ONIVYDE®-like). Taken together, IR/SS30-LP displayed redox-responsive release of IR, ultra-high loading and enhanced anti-tumor activity, which has great potential for clinical application as a new generation of IR liposomal formulation.

Sterically Stabilized Polyionic Complex Nanogels of Chitosan Lysate and PEG-b-Polyglutamic Acid Copolymer for the Delivery of Irinotecan Active Metabolite (SN-38)

BACKGROUND

Poly Ionic Complex (PIC) nanogels are promising delivery systems with numerous attractions such as simple, fast, and organic solvent-free particle formation and mild drug loading conditions. Among polyelectrolytes, poly (L-amino acid) copolymers, such as poly (ethylene glycol)-block-poly (L-glutamic acid) copolymers (PEG-b-PGlu) are interesting biocompatible and biodegradable candidates bearing carboxylic acid functional groups.

OBJECTIVE

Aiming to solubilize and to preserve short-acting irinotecan active metabolite (SN38), sterically stabilized PIC nanogels were prepared through electrostatic charge neutralization between PEG-b-PGlu and chitosan lysate, a polycationic natural polymer obtained through digestion of chitosan by hydrogen peroxide oxidation and is soluble in a wide range of pH.

METHODS

Synthesis of PEG-b-PGlu was accomplished by N-carboxy anhydride polymerization of γ -benzyl L-glutamic acid, which is initiated by methoxy PEG-NH2 and successive debenzylation reaction.

RESULTS

The resulting block copolymer was characterized by FTIR, ¹H-NMR, and Size Exclusion Chromatography (SEC). Self-assembling properties of the PIC nanogels were investigated by pyrene assay, Dynamic Light Scattering (DLS), and Transmission Electron Microscopy (TEM), indicating the formation of homogeneous spherical particles with a mean size of 28 nm at the PEGb- PGlu concentrations/LMWC weight ratio of 5:1. Upon direct loading of SN38, the drug solubility enhanced more than 4×10³ folds with a mean loading efficiency of 89% and the drug loading of 30%. PIC nanogels exhibited zeta potential of +1 mV, acceptable biocompatibility, and superior cytotoxicity in murine colorectal carcinoma (CT26 cell line) compared to free drug.

CONCLUSION

In addition, the PIC nanogels provided SN38 protection against hydrolytic degradation in physiologic conditions. Conclusively, the well-tuned PIC nanogels are suggested as a potentially biocompatible nanocarrier for SN38 delivery.

Mechanism and optimization of supramolecular complexation-enhanced fluorescence spectroscopy for the determination of SN-38 in plasma and cells

Quantitative detection of two different forms of SN-38 in biological samples is, currently, cumbersome and difficult. A revisit to the mechanism of supramolecular complexation-enhanced fluorescence spectroscopy helps to optimize the determination of SN-38 in plasma and the cellular pharmacokinetics in A549 cells based on the supramolecular complexation. Firstly, the inclusion mechanism dominated by thermodynamic constants was determined by measuring kinetic/thermodynamic parameters (k_on , k_off , ΔG, ΔH, ΔS). On this basis, the best effect of fluorescence sensitization was optimized through screening the interaction conditions (cyclodextrin species and concentrations, drug levels, temperature, pH of the buffer, and reaction time). Furthermore, the proportional relationship between the concentration of the inclusion complex and the fluorescence intensity was confirmed. Finally, a highly sensitive, selective spectrofluorimetric method was established and validated for quantitative analysis of the lactone and carboxylate molecular states of SN-38 plasma levels in rats and cell membrane transfer kinetics in A549 cell lines. The limits of detection for the lactone and carboxylate forms in plasma were found to be 0.44 ng·ml^-1 and 0.28 ng·ml^-1 , respectively. Precision and accuracy met the requirements of biological samples analysis. The proposed detection method provided a reference for elucidating the biodistribution of SN-38.

Ultrasound-triggered therapeutic microbubbles enhance the efficacy of cytotoxic drugs by increasing circulation and tumor drug accumulation and limiting bioavailability and toxicity in normal tissues

Most cancer patients receive chemotherapy at some stage of their treatment which makes improving the efficacy of cytotoxic drugs an ongoing and important goal. Despite large numbers of potent anti-cancer agents being developed, a major obstacle to clinical translation remains the inability to deliver therapeutic doses to a tumor without causing intolerable side effects. To address this problem, there has been intense interest in nanoformulations and targeted delivery to improve cancer outcomes. The aim of this work was to demonstrate how vascular endothelial growth factor receptor 2 (VEGFR2)-targeted, ultrasound-triggered delivery with therapeutic microbubbles (thMBs) could improve the therapeutic range of cytotoxic drugs. Methods: Using a microfluidic microbubble production platform, we generated thMBs comprising VEGFR2-targeted microbubbles with attached liposomal payloads for localised ultrasound-triggered delivery of irinotecan and SN38 in mouse models of colorectal cancer. Intravenous injection into tumor-bearing mice was used to examine targeting efficiency and tumor pharmacodynamics. High-frequency ultrasound and bioluminescent imaging were used to visualise microbubbles in real-time. Tandem mass spectrometry (LC-MS/MS) was used to quantitate intratumoral drug delivery and tissue biodistribution. Finally, 89Zr PET radiotracing was used to compare biodistribution and tumor accumulation of ultrasound-triggered SN38 thMBs with VEGFR2-targeted SN38 liposomes alone. Results: ThMBs specifically bound VEGFR2 in vitro and significantly improved tumor responses to low dose irinotecan and SN38 in human colorectal cancer xenografts. An ultrasound trigger was essential to achieve the selective effects of thMBs as without it, thMBs failed to extend intratumoral drug delivery or demonstrate enhanced tumor responses. Sensitive LC-MS/MS quantification of drugs and their metabolites demonstrated that thMBs extended drug exposure in tumors but limited exposure in healthy tissues, not exposed to ultrasound, by persistent encapsulation of drug prior to elimination. 89Zr PET radiotracing showed that the percentage injected dose in tumors achieved with thMBs was twice that of VEGFR2-targeted SN38 liposomes alone. Conclusions: thMBs provide a generic platform for the targeted, ultrasound-triggered delivery of cytotoxic drugs by enhancing tumor responses to low dose drug delivery via combined effects on circulation, tumor drug accumulation and exposure and altered metabolism in normal tissues.

Nanoparticle-mediated in vitro delivery of E4orf1 to preadipocytes is a clinically relevant delivery system to improve glucose uptake

OBJECTIVE

Impaired glycemic control is a common comorbidity of obesity. E4orf1(E4), an adenovirus-derived protein, reduces the activity of insulin receptor substrate (IRS), yet activates Akt and promotes the membrane translocation of GLUT4, resulting in better glycemic control in mice. To develop a clinically suitable delivery system, here we constructed and tested liposome nanoparticles (NP), to deliver E4 to preadipocytes.

METHODS

Glutathione-S-transferase (GST)-tagged E4 was encapsulated in Rhodamine-phosphatidylethanolamine (PE)-tagged soy-phosphatidylcholine-NP. The NP were characterized. Preadipocytes were treated with free E4, E4 containing NP (E4 NP) or E4-free NP (void NP).

RESULTS

For void and E4 NP, the average size was ~150 and 130 nm, PDI was ~0.25 and 0.27, and Zeta potential was -23 and -25, respectively. The average encapsulation efficiency (EE) was ~50%. Cells treated with E4 showed maximum GST expression and Rhodamine signals at 24 h. The presence of E4 in cells was confirmed at 24, 48, and 72 h. At 72 h after exposure, E4 NP significantly decreased pTyr-IRS, yet increased pAkt protein abundance, membrane translocation of GLUT4, and glucose uptake, compared with cells treated with void NP. Free E4 (without NP) had no effect.

CONCLUSIONS

NP-mediated delivery of E4 promotes glucose uptake in preadipocytes. The next step is to test the efficacy of this clinically compatible delivery approach in vivo.

Theranostics system caged in human serum albumin as a therapy for breast tumors

Biomimetic materials are attracting increasing attention in the field of drug delivery due to their low immunogenicity, good biocompatibility and degradability.

Novel carrier-free nanoparticles composed of 7-ethyl-10-hydroxycamptothecin and chlorin e6: Self-assembly mechanism investigation and in vitro/in vivo evaluation

The combination therapy strategy based on both chemotherapy and photodynamic therapy (PDT) exhibits great potential for advanced cancer treatment. Multimodal nanodrug delivery systems based on both chemotherapeutic drug and photodynamic agent have been proven to possess excellent synergistic efficacy. In this study, 7-ethyl-10-hydroxycamptothecin (SN38) and chlorin e6 (Ce6) were co-assembled into novel carrier-free nanoparticles (SN38/Ce6 NPs) via simple antisolvent precipitation method. As expected, SN38/Ce6 NPs exhibited uniform morphology with a particle size of around 150 nm and a zeta potential of about -30 mV, good stability in aqueous solution/at lyophilized state and high cellular uptake efficiency against murine mammary carcinoma (4T1) cell lines. Besides, enhanced singlet oxygen generation capacity of the nanoparticles was both observed in test-tube and in 4T1 cell lines in contrast with Ce6 injection. Moreover, a ∼85 % inhibition rate of SN38/Ce6 NPs with laser was detected, which was significantly higher (P < 0.05) than those without laser (∼65 %) and injections (less than 20 %), verified the excellent synergistic antitumor efficacy of the nanoparticles due to combined chemo-photodynamic therapy, enhanced tumor accumulation and higher cellular internalization. Notably, chemical thermodynamic method and molecular dynamics (MD) simulations supplied solid data and visual images to estimate the driving forces for the self-assembly process of the carrier-free nanoparticles as primary hydrophobic interactions (π-π stacking) and subordinate hydrogen bonds. Conclusively, the above self-assembled carrier-free nanoparticles represented a promising synergistic anticancer strategy capable of maximal therapeutic efficacy and minimal systemic toxicity. Moreover, the application of thermodynamic method together with MD simulations in the investigation of NPs self-assembly process also provided new ideas for the assembly mechanism exploration of more complicated nanodrug delivery system.

Topoisomerase inhibitors: Pharmacology and emerging nanoscale delivery systems

Topoisomerase enzymes have shown unique roles in replication and transcription. These enzymes which were initially found in Escherichia coli have attracted considerable attention as target molecules for cancer therapy. Nowadays, there are several topoisomerase inhibitors in the market to treat or at least control the progression of cancer. However, significant toxicity, low solubility and poor pharmacokinetic properties have limited their wide application and these characteristics need to be improved. Nano-delivery systems have provided an opportunity to modify the intrinsic properties of molecules and also to transfer the toxic agent to the target tissues. These delivery systems leads to the re-introduction of existing molecules present in the market as novel therapeutic agents with different physicochemical and pharmacokinetic properties. This review focusses on a variety of nano-delivery vehicles used for the improvement of pharmacological properties of topoisomerase inhibitors and thus enabling their potential application as novel drugs in the market.

High Potency of SN-38-Loaded Bovine Serum Albumin Nanoparticles Against Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer with a worse prognosis than other types. There are currently no specific approved treatments for TNBC. Albumin is a promising biomimetic material that may be fabricated into nanoparticles to possibly exert passive effects on targeted tumors. Irinotecan has been extensively used in clinical settings, although a high dosage is required due to its low efficiency of conversion into the active metabolite SN-38, also known as 7-ethyl-10-hydroxy-camptothecin. The aim of this work was to optimize SN-38-loaded bovine serum albumin nanoparticles (sBSANPs) and evaluate their potency against TNBC. The sBSANPs were characterized by a small size of about 134-264 nm, a negative charge of -37 to -40 mV, an entrapment efficiency of 59-71%, and a particle yield of 65-86%. The cytotoxicity assays using sBSANPs showed a higher potency specifically against both MDA-MB-468 and MDA-MB-231 cells (ER-, PR-, HER2-) compared to MCF-7 (ER+, PR+, HER2-), and exhibited an extremely low IC₅₀ at the nanomolar levels (2.01-6.82 nM). The release profiles indicated that SN-38 presented an initial burst release within 12 h, and sBSANPs had a slow release pattern. Flow cytometry results showed that the fluorescence intensity of sBSANPs was significantly higher than that of the control group. The confocal images also confirmed that sBSANPs were taken up by MDA-MB-468 cells. Moreover, we found that a larger BSANP size resulted in an increased hemolytic effect. In vivo animal studies demonstrated that loading of SN-38 into bovine serum albumin nanoparticles could minimize the initial concentration without extending the elimination half-life, but significantly minimized the Cmax (p < 0.001) as compared with irinotecan treatment.

Excipient-free nanodispersion of 7-ethyl-10-hydroxycamptothecin exerts potent therapeutic effects against pancreatic cancer cell lines and patient-derived xenografts

Irinotecan (CPT-11) is an anti-tumor drug and formulated as nanomedicines to reduce side effects and improve efficacy. In vivo, CPT-11 must be hydrolyzed by carboxylesterase to its active form 7-ethyl-10-hydroxycamptothecin (SN-38) to exert anti-tumor activity, but the lack of this enzyme in humans causes inefficient generation of SN-38. Thus, direct delivery of SN-38, not relying on carboxylesterase, will potentially achieve higher efficacy. However, it is difficult to effectively formulate SN-38 using current excipients due to its hydrophobicity and tendency to crystallize. Herein, we report the nanodispersion of SN-38 with its amphiphilic prodrug, CPT-11, as an effective treatment for pancreatic cancer (PC). SN-38 and CPT-11 formed stable nanoparticles without any other excipients, and showed potent cytotoxicity against PC cells in vitro, slowed tumor growth in vivo, namely subcutaneously and orthotopically xenografted mice, with minimal adverse effects, and prolonged their overall survival. Even in clinically-relevant patient-derived xenograft (PDX) models, the nanodispersion showed greater anti-tumor efficacy than CPT-11. Importantly, the nanodispersion directly released SN-38, resulting in carboxylesterase-independent anti-tumor activity, in contrast to carboxylesterase-dependent CPT-11. These characteristics may enable the excipient-free nanodispersion to exert potent therapeutic effects in patients.

A polymeric micelle with an endosomal pH-sensitivity for intracellular delivery and enhanced antitumor efficacy of hydroxycamptothecin

Amphiphilic poly(ethylene glycol)-imino-poly(benzyl-l-aspartate) (PIPA) and poly(ethylene glycol)-poly(benzyl-l-aspartate) (PPA) block copolymers were synthesized as pH-responsive and pH-nonresponsive copolymers, respectively. Polymer micelles were fabricated by the film dispersion method, and hydroxycamptothecin (HCPT) was physically encapsulated into the micelles. The average diameter of the HCPT-loaded PIPA micelles (PIPAH micelles) was approximately 230 nm, which was slightly smaller than that of the HCPT-loaded PPA micelles (PPAH micelles, approximately 260 nm). The drug-loading content and encapsulation efficiency of the PIPAH micelles (3.33% and 68.89%, respectively) were slightly higher than those of the PPAH micelles (2.90% and 59.68%, respectively). The PIPAH micelles exhibited better colloid stability, storage stability, and plasma stability than the PPAH micelles. Drug release from the PIPAH micelles with imino groups was pH dependent, and more than 75% or 65% of the loaded HCPT was released within 24 h in weakly acidic media (pH 5.0 or 6.0, respectively). An in vitro cell assay demonstrated that the pH-sensitive micelles exhibited potent suppression of cancer cell proliferation and little cytotoxicity on normal cells. Additionally, these micelles could be efficiently internalized by the tumor cells through macropinocytosis- and caveolin-mediated endocytotic pathways. HCPT-loaded micelles had longer circulation time than the HCPT solution in a pharmacokinetic study. In vivo antitumor experiments indicate that the PIPAH micelles had better antitumor efficacy than the pH-insensitive PPAH micelles and the HCPT solution. Therefore, the pH-responsive PIPAH micelles have great potential for high-efficiency delivery of HCPT. STATEMENT OF SIGNIFICANCE: In this study, a new type of pH-responsive amphiphilic copolymer, poly(ethylene glycol)-imino-poly(benzyl-l-aspartate) (PIPA) block copolymer, was synthesized. This copolymer had then self-assembled to form nanomicelles for tumor intracellular delivery of hydroxycamptothecin (HCPT) for the first time. In in vitro test, the PIPAH micelles exhibited adequate stability and pH-dependent drug release. To one's excitement, the PIPAH micelles exhibited better antitumor efficacy and biosafety than the pH-insensitive micelles (PPAH) and the HCPT solution in in vitro and in vivo antitumor experiments. Therefore, the pH-responsive micelles in this study have significant potential to be used for high-performance delivery of HCPT and potentially for the targeted delivery of other cancer therapeutic agents. The polymer designed in this study can be used as a carrier of poorly soluble drugs or other active ingredients.

One-step mechanochemical preparation and prominent antitumor activity of SN-38 self-micelle solid dispersion

Purpose

The purpose of this study was to overcome the clinical defects of 7-ethyl-10-hydroxycamptothecin (SN-38) and explore its characteristics and antitumor effects.

Materials and methods

An amorphous solid dispersion of SN-38 with disodium glycyrrhizin (Na₂GA) was prepared by mechanical ball milling (Na₂GA/SN-38-BM). Moreover, an untreated mixture of Na₂GA and SN-38 (Na₂GA/SN-38-UM), a pure drug SN-38, was prepared for comparison with Na₂GA/SN-38-BM. The samples were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), dynamic light scattering, and transmission electron microscopy. Then, further in vitro and in vivo studies were performed including cell uptake, cytotoxicity, antitumor efficacy, tissue distribution, and histopathological evaluation (H&E staining).

Results

SN-38 loaded in Na₂GA was self-formed as nano-micelles in water. The particle size of nano-micelle was 69.41 nm and ζ-potential was -42.01 mV. XRD and SEM analyses showed that the ball milling transformed SN-38 crystals into amorphous form and that solubility increased by 189 times. Compared with SN-38 and Na₂GA/SN-38-UM, Na₂GA/SN-38-BM has a stronger cytotoxicity to tumor cells and exhibited a significant inhibition of tumor growth. Then, pharmacokinetic studies showed that the bioavailability of Na₂GA/SN-38-BM was about four times that of SN-38 suspension.

Conclusion

Na₂GA/SN-38-BM (69 nm, -42 mV) nanoparticles which had excellent phar-macokinetic and distribution properties can dramatically enhance the anticancer efficacy of SN-38 in vitro and in vivo, suggesting a promising formulation for efficient anticancer therapy.

Cancer Chemotherapy by Novel Bio-active Natural Products: Looking Towards the Future

Background:

Cancer is the second leading cause of death globally and accounted for 8.8 million deaths annually in humans. Lung, prostate, colorectal, stomach and liver cancer are the most common types of cancer in men, while breast, colorectal, lung, cervix and stomach cancer are the most common among women. Numerous drugs that the US Food and Drug Administration (FDA) have approved for use in cancer therapy are derived from plants, including taxanes such as paclitaxel and vinca alkaloids such as vincristine and vinblastine. Still, there is an intense need for a search for numerous bioactive sources to develop a novel anti-cancer drug to overcome this chronic disorder. About more than thirty plants derived natural products have been isolated till date and are currently under clinical trials. As per literature survey from various journals and texts has been found to be novel medicinal agents from bioactive sources are clinically active against various types of cancer cells.

Conclusion:

Current review has been highlighted on the novel medicinal agents from plant sources have potential effects against many types of cancer, which have been supported by clinical trials. The main findings of these active novel medicinal agents were also summarized and discussed here.

Synthesis of a SN38 prodrug grafted to amphiphilic phosphorylcholine polymers and their prodrug miceller properties

Polymer prodrug micelles, combining the advantages of prodrugs and polymer micelles, can greatly improve the solubility, permeability and stability of drugs.

Microfluidic Manufacturing of SN-38-Loaded Polymer Nanoparticles with Shear Processing Control of Drug Delivery Properties

Two-phase gas-liquid microfluidic reactors provide shear processing control of SN-38-loaded polymer nanoparticles (SN-38-PNPs). We prepare SN-38-PNPs from the block copolymer poly(methyl caprolactone- co-caprolactone)- block-poly(ethylene oxides) (P(MCL- co-CL)- b-PEO) using bulk and microfluidic methods and at different drug-to-polymer loading ratios and on-chip flow rates. We show that, as the microfluidic flow rate ( Q) increases, encapsulation efficiency and drug loading increase and release half times increase. Slower SN-38 release is obtained at the highest Q value ( Q = 400 μL/min) than is achieved using a conventional bulk preparation method. For all SN-38-PNP formulations, we find a dominant population (by number) of nanosized particles (<50 nm) along with a small number of larger aggregates (>100 nm). As Q increases, the size of aggregates decreases through a minimum and then increases, attributed to a flow-variable competition of shear-induced particle breakup and shear-induced particle coalescence. IC₂₅ and IC₅₀ values of the various SN-38-PNPs against MCF-7 cells show strong flow rate dependencies that mirror trends in particle size. SN-38-PNPs manufactured on-chip at intermediate flow rates show both minimum particle sizes and maximum potencies with a significantly lower IC₂₅ value than the bulk-prepared sample. Compared to conventional bulk methods, microfluidic shear processing in two-phase reactors provides controlled manufacturing routes for optimizing and improving the properties of SN-38 nanomedicines.

Preparation of Glycyrrhetinic Acid Liposomes Using Lyophilization Monophase Solution Method: Preformulation, Optimization, and In Vitro Evaluation

In this study, glycyrrhetinic acid (GA) liposomes were successfully prepared using lyophilization monophase solution method. Preformulation studies comprised evaluation of solubility of soybean phosphatidylcholine (SPC), cholesterol, and GA in tert-butyl alcohol (TBA)/water co-solvent. The influences of TBA volume percentage on sublimation rate were investigated. GA after lyophilization using TBA/water co-solvent with different volume percentage was physicochemically characterized by DSC, XRD, and FTIR. The XRD patterns of GA show apparent amorphous nature. FTIR spectroscopy results show that no chemical structural changes occurred. Solubility studies show aqueous solubility of GA is enhanced. The optimum formulation and processing variables of 508 mg SPC, 151 mg cholesterol, 55% volume percentage of TBA, 4:1 trehalose/SPC weight ratio were obtained after investigating by means of Box-Benhnken design and selection experiment of lyoprotectant. Under the optimum conditions, satisfactory encapsulation efficiency (74.87%) and mean diameter (191 nm) of reconstituted liposomes were obtained. In vitro drug release study showed that reconstituted liposomes have sustained-release properties in two kinds of release medium. Furthermore, in vitro cell uptake study revealed that uptake process of drug-loaded liposomes by Hep G2 cells is time-dependent.

Liposomal codelivery of an SN38 prodrug and a survivin siRNA for tumor therapy

Purpose

A liposome-based siRNA–drug combination was evaluated as a potential therapeutic strategy to improve the curative effect.

Methods

A topoisomerase inhibitor SN38 prodrug was combined with a survivin siRNA through codelivery using transferrin (Tf)-L-SN38/P/siRNA. In this combination, SN38 was conjugated to the cell penetrating peptide TAT through a polyethylene glycol (PEG) linker to synthesize TAT-PEG-SN38. The amphiphilic TAT-PEG-SN38 was used as an ingredient of liposomes to improve the cellular uptake. Protamine was added to form an electrostatic complex with siRNA in the core of the liposomes. Tf was introduced to enable tumor cell targeting of liposomes (Tf-L-SN38/P/siRNA).

Results

Tf-L-SN38/P/siRNA exhibited a particle size of 148 nm and a ζ-potential of +7.8 mV. The cellular uptake and antitumor activity were dependent on Tf receptor targeting, TAT-PEG-SN38, and siRNA codelivery. Tf-L-SN38/P/siRNA was shown to be considerably more effective than liposomes carrying individual components. This combination induced potent tumor inhibition (76.8%) in HeLa cell xenograft tumor-bearing nude mice.

Conclusion

These data indicated that Tf-L-SN38/P/siRNA was an effective system for codelivery of SN38 and a survivin siRNA and that its therapeutic potential deserved further evaluation.

Reprogramming Cells for Synergistic Combination Therapy with Nanotherapeutics against Uveal Melanoma

Uveal melanoma (UM) is the most common primary intraocular malignant tumor in adults and around half of the patients develop metastasis and die shortly after because of the lack of effective therapies for metastatic UM. Consequently, new therapeutic approaches to this disease are welcome. In this regard, microRNAs have been shown to have a key role in neoplasia progression and have the potential to be used as therapeutic tools. In addition, in different cancers including UM, a particular microRNA signature appears that is different from healthy cells. Thus, restoring the regular levels of microRNAs could restore the normal behavior of cells. In this study, four microRNAs downregulated in UM have been chosen to reprogram cancer cells, to promote cell death or increase their sensitivity to the chemotherapeutic SN38. Furthermore, to improve the internalization, stability and/or solubility of the therapeutic molecules employed in this approach, gold nanoparticles (AuNPs) were used as carriers. Remarkably, this study found a synergistic effect when the four oligonucleotides were employed and when the chemotherapeutic drug was added.

A novel microfluidic liposomal formulation for the delivery of the SN-38 camptothecin: characterization and in vitro assessment of its cytotoxic effect on two tumor cell lines

PURPOSE

Irinotecan (CPT-11) and SN-38 - its active metabolite - are alkaloid-derived topoisomerase I interactive compounds widely used in various cancer therapy protocols. To solve the problems associated with the instability of their lactone ring at physiological pH and with the extreme insolubility of SN-38, the development of delivery carriers (eg, liposomes) has been considered a subject of unquestionable medical interest. This article focuses on the development of an alternative protocol to the classical lipid-film hydration procedures to obtain a pharmaceutical formulation for SN-38.

METHODS

SN-38-loaded liposomes (SN-38lip) were produced by microemulsification, without a prior lipid-film preparation step, and characterized by different methods. Formulation parameters were determined by photon correlation spectroscopy, and the SN-38 entrapment efficiency was evaluated by absorbance spectroscopy. SN-38lip was obtained as a dry, white powder by lyophilization. MTT and LDH assays were conducted to assess the cytotoxic effect of SN-38, both in liposomal (SN-38lip) and solubilized form (SN-38sol); flow cytometry was used to quantify SN-38 uptake and to analyze cell-cycle phase distribution after drug exposure.

RESULTS

Microfluidic, stable, and controlled sized, negatively charged liposomes, with high SN-38 incorporation efficiency into egg yolk phosphatidylcholine (EPC)/L-α-dioleoyl-phospathidylserine (DOPS) (9:1) vesicles (SN-38lip), were prepared. A lyophilized powder of SN-38lip, easily reconstitutable while retaining physicochemical parameters, was finally obtained. The efficacy of SN-38lip was assessed by in vitro studies with two tumor cell lines (HeLa and Caco-2) and compared with that of SN-38sol. It demonstrated the highest uptake of SN-38lip, in accordance with its highest cytotoxicity effect, in comparison with that of SN-38sol. In addition, different cell-cycle alterations were induced in both cell lines by the liposomal formulation.

CONCLUSION

The results highlight the potential usefulness of the procured SN-38 liposomal formulation and provide the basis for conducting in vivo studies that allow the development of alternative strategies for colorectal cancer treatment.

Encapsulation and Enhanced Delivery of Topoisomerase I Inhibitors in Functionalized Carbon Nanotubes

The topoisomerase I inhibitors SN-38 and camptothecin (CPT) have shown potent anticancer activity, but water insolubility and metabolic instability limits their clinical application. Utilizing carbon nanotubes as a protective shell for water-insoluble SN-38 and CPT while maintaining compatibility with aqueous media via a carboxylic acid-functionalized surface can thus be a strategy to overcome this limitation. Through hydrophobic-hydrophobic interactions, SN-38 and CPT were successfully encapsulated in carboxylic acid functionalized single-walled carbon nanotubes and dispersed in water. The resulting cell proliferation inhibition and drug distribution profile inside the cells suggest that these drug-encapsulated carbon nanotubes can serve as a promising delivery strategy for water-insoluble anticancer drugs.

Macrophages as an active tumour-targeting carrier of SN38-nanoparticles for cancer therapy

Taking advantage of their enhanced permeability and retention (EPR) effect, nanomedicines have been extensively studied for targeted drug delivery to tumour tissues. However, tumour heterogeneity restricts the EPR effect and drug penetration into tumours, and nanoformulations only generate a limited therapeutic improvement in clinical settings. Macrophages have the inherent ability of tumour homing, stealth in blood circulation, and phagocytosis of particles. In this study, we used peritoneal macrophages as carriers for the delivery of SN38 nanoparticles (SN38-NPs) for cancer treatment. SN38-NPs were internalised by macrophages without any obvious effect on viability and migration, and not only induced apoptosis of tumour cells in vitro, but also accumulated in tumour tissues in vivo. In addition, the macrophage-based delivery system for SN38-NPs showed improved therapeutic effect than an equivalent dose of CPT-11 in an A549 subcutaneous tumour model.

Liposome-loaded thermo-sensitive hydrogel for stabilization of SN-38 via intratumoral injection: optimization, characterization, and antitumor activity

Main challenges of the clinical use of 7-ethyl-10-hydroxycamptothecin (SN-38) are its facile transition between the active lactone form (SN-38 A) and the inactive carboxylate form (SN-38I) under physiological conditions and its low solubility. The purpose of this study was to develop a thermo-sensitive hydrogel system with acidic SN-38 liposomes (SN-38-Lip-Gel) for local chemotherapy to solve these problems and to evaluate its antitumor activity and tissue distribution in tumor-bearing mice. A study of structural conversion between SN-38I and SN-38 A under various pH conditions indicated that acidic solution could inhibit the conversion. Namely, a preparation with low pH was essential to stabilize lactone form of SN-38. SN-38-Lip-Gel had an appropriate gelation time (GT) at 25/37 °C. The particle size of SN-38-Lip-Gel was similar to that of SN-38-Lip. SN-38-Lip-Gel showed a slower release than SN-38-Lip in vitro. SN-38-Lip-Gel suggested pH-dependent stability, the percentage of SN-38 A remaining decreased along with the increasing pH. In vivo studies SN-38-Lip-Gel showed better antitumor efficacy and lower systemic toxicity compared with other groups at the same drug dose. In conclusion, SN-38-Lip-Gel could improve the effective use of SN-38 by stabilizing the lactone form, extending the drug release, providing a high local drug concentration, and reducing systemic toxicity.