A sensitive bioanalytical ultra-high-performance liquid chromatography-tandem mass spectrometry method for the simultaneous quantitation of lactone and carboxylate forms of topotecan in plasma and vitreous.

Topotecan (TPT) is used in the treatment of retinoblastoma, the most common malignant intraocular tumor in children. TPT undergoes pH-dependent hydrolysis of the lactone ring to the ring-opened carboxylate form, with the lactone form showing antitumor activity. A selective, and highly sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed for the determination of both forms of TPT in one mobile phase composition in plasma and vitreous humor matrices. The method showed an excellent linear range of 0.375-120 ng/mL for the lactone. For the carboxylate, the linear range was from 0.75 to 120 ng/mL. The matrix effect and the recovery for the lactone ranged from 98.5% to 106.0% in both matrices, for the carboxylate form, it ranged from 94.9% to 101.2%. The dynamics of the transition between TPT lactone and TPT carboxylate were evaluated at different pH environments. The stability of TPT forms was assessed in plasma and vitreous humor at 8 and 37°C and a very fast conversion of lactone to carboxylate form occurred at 37°C in both matrices. The method developed facilitates the investigation of TPT pharmacodynamics and the release kinetics in the development of the innovative local drug delivery systems.

Self-assembled ordered AuNRs-modified electrodes for simultaneous determination of dopamine and topotecan with improved data reproducibility.

Gold nanomaterials have been widely explored in electrochemical sensors due to their high catalytic property and good stability in multi-medium. In this paper, the reproducibility of the signal among batches of gold nanorods (AuNRs)-modified electrodes was investigated to improve the data stabilization and repeatability. Ordered and random self-assembled AuNRs-modified electrodes were used as electrochemical sensors for the simultaneous determination of dopamine (DA) and topotecan (TPC), with the aim of obtaining an improved signal stability in batches of electrodes and realizing the simultaneous determination of both substances. The morphology and structure of the assemblies were analyzed and characterized by UV-Vis spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray powder diffraction (XRD). Electrochemical studies showed that the ordered AuNRs/ITO electrodes have excellent signal reproducibility among several individuals due to the homogeneous mass transfer in the ordered arrangement of the AuNRs. Under the optimized conditions, the simultaneous detection results of DA and TPC showed good linearity in the ranges 1.75-45 µM and 1.5-40 µM, and the detection limits of DA and TPC were 0.06 µM and 0.17 µM, respectively. The results showed that the prepared ordered AuNR/ITO electrode had high sensitivity, long-term stability, and reproducibility for the simultaneous determination of DA and TPC, and it was expected to be applicable for real sample testing.

Dual modulation of blue-fluorescent carbon dots for simultaneous detection of topotecan and pantoprazole.

This study introduces a novel approach for the simultaneous determination of topotecan (TOP) and pantoprazole (PNT), two drugs whose interaction is critical in clinical applications. The significance of this study originates from the need to understand the pharmacokinetic changes of TOP after PNT administration, which can inform necessary dose adjustments of TOP. To achieve this, nitrogen blue emissive carbon dots (B@NCDs) were produced and employed due to their unique fluorescent properties. When TOP is added to B@NCDs, it exhibits strong native fluorescence at 545 nm without influencing the B@NCDs' fluorescence at 447 nm. Conversely, PNT causes quenching of B@NCDs fluorescence, a property that enables the distinct detection of both drugs. The B@NCDs were fully characterized using different techniques, including ultraviolet-visible spectrophotometry, fluorescence analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), and FTIR spectroscopy. The proposed method demonstrated excellent linearity, selectivity, and sensitivity, with low detection limits (LOD, S/N = 3); 0.0016 µg mL-1 for TOP and 0.36 µg mL-1 for PNT. Applied to spiked rabbit plasma samples, this method offers a new approach for evaluating the pharmacokinetic interaction between TOP and PNT. It enables the determination of all pharmacokinetic parameters of TOP before and after coadministration with PNT, providing essential insights into whether dose adjustments are necessary. This research not only contributes to the field of drug monitoring and interaction studies but also exemplifies the potential of B@NCDs in complex biological matrices, paving the way for further pharmacological and therapeutic applications.

Green Light-Triggered Intraocular Drug Release for Intravenous Chemotherapy of Retinoblastoma.

Retinoblastoma is one of the most severe ocular diseases, of which current chemotherapy is limited to the repetitive intravitreal injections of chemotherapeutics. Systemic drug administration is a less invasive route; however, it is also less efficient for ocular drug delivery because of the existence of blood-retinal barrier and systemic side effects. Here, a photoresponsive drug release system is reported, which is self-assembled from photocleavable trigonal small molecules, to achieve light-triggered intraocular drug accumulation. After intravenous injection of drug-loaded nanocarriers, green light can trigger the disassembly of the nanocarriers in retinal blood vessels, which leads to intraocular drug release and accumulation to suppress retinoblastoma growth. This proof-of-concept study would advance the development of light-triggered drug release systems for the intravenous treatment of eye diseases.

The First Berberine-Based Inhibitors of Tyrosyl-DNA Phosphodiesterase 1 (Tdp1), an Important DNA Repair Enzyme.

A series of berberine and tetrahydroberberine sulfonate derivatives were prepared and tested against the tyrosyl-DNA phosphodiesterase 1 (Tdp1) DNA-repair enzyme. The berberine derivatives inhibit the Tdp1 enzyme in the low micromolar range; this is the first reported berberine based Tdp1 inhibitor. A structure-activity relationship analysis revealed the importance of bromine substitution in the 12-position on the tetrahydroberberine scaffold. Furthermore, it was shown that the addition of a sulfonate group containing a polyfluoroaromatic moiety at position 9 leads to increased potency, while most of the derivatives containing an alkyl fragment at the same position were not active. According to the molecular modeling, the bromine atom in position 12 forms a hydrogen bond to histidine 493, a key catalytic residue. The cytotoxic effect of topotecan, a clinically important topoisomerase 1 inhibitor, was doubled in the cervical cancer HeLa cell line by derivatives 11g and 12g; both displayed low toxicity without topotecan. Derivatives 11g and 12g can therefore be used for further development to sensitize the action of clinically relevant Topo1 inhibitors.

F7 and topotecan co-loaded thermosensitive liposome as a nano-drug delivery system for tumor hyperthermia.

In order to enhance the targeting efficiency and reduce anti-tumor drug's side effects, topotecan (TPT) and F7 were co-loaded in thermosensitive liposomes (F7-TPT-TSL), which show enhanced permeability and retention in tumors, as well as local controlled release by heating in vitro. TPT is a water-soluble inhibitor of topoisomerase I that is converted to an inactive carboxylate structure under physiological conditions (pH 7.4). F7 is a novel drug significantly resistant to cyclin-dependent kinase but its use was restricted by its high toxicity. F7-TPT-TSL had excellent particle distribution (about 103 nm), high entrapment efficiency (>95%), obvious thermosensitive property, and good stability. Confocal microscopy demonstrated specific higher accumulation of TSL in tumor cells. MTT proved F7-TPT-TSL/H had strongest cell lethality compared with other formulations. Then therapeutic efficacy revealed synergism of TPT and F7 co-loaded in TSL, together with hyperthermia. Therefore, the F7-TPT-TSL may serve as a promising system for temperature triggered cancer treatment.

Optimizing the storage of chemotherapeutics for ophthalmic oncology: stability of topotecan solution for intravitreal injection.

BACKGROUND: . Intravitreal administration of topotecan shows activity against tumor vitreous seeding in the conservative treatment of retinoblastoma, a malignant tumor originated in the retina of small children. Adequate storage of the intravitreal topotecan solution would allow immediate availability for patients at health care institutions. The goal of the work was to address the stability of the intravitreal topotecan formulation upon reconstitution. MATERIALS AND METHODS: . Intravitreal topotecan solutions were reconstituted (at a concentration of 0.2 mg topotecan in 1 mL saline solution vehicle, aliquoted in 1 mL plastic syringes) and stored either frozen or at room temperature for different times. Topotecan content was analyzed at time zero and at different conditions using a high performance liquid chromatography method to quantify topotecan lactone (active) and to detect its pH-dependent hydrolysis product, the open carboxylate. RESULTS: . We found that intravitreal topotecan syringes remained stable at room temperature at least for 24 h, at least for 167 days upon stored frozen at -20°C, and up to 8 h after thawing at day 6. The degradation carboxylate product did not appear in the analyzed thawed samples during the whole study. CONCLUSIONS: . This study confirms the stability of frozen intravitreal topotecan syringes and will help optimize the use of this chemotherapy modality at institutions with low resources. Storage of aliquots will also help reduce personnel exposure to chemotherapy at hospital pharmacies.

The "adductome": A limited repertoire of adducted proteins in human cells.

Proteins form adducts with nucleic acids in a variety of contexts, and these adducts may be cytotoxic if not repaired. Here we apply a proteomic approach to identification of proteins adducted to DNA or RNA in normally proliferating cells. This approach combines RADAR fractionation of proteins covalently bound to nucleic acids with quantitative mass spectrometry (MS). We demonstrate that "RADAR-MS" can quantify induction of TOP1- or TOP2-DNA adducts in cells treated with topotecan or etoposide, respectively, and also identify intermediates in physiological adduct repair. We validate RADAR-MS for discovery of previously unknown adducts by determining the repertoires of adducted proteins in two different normally proliferating human cell lines, CCRF-CEM T cells and GM639 fibroblasts. These repertoires are significantly similar with one another and exhibit robust correlations in their quantitative profiles (Spearman r = 0.52). A very similar repertoire is identified by the classical approach of CsCl buoyant density gradient centrifugation. We find that in normally proliferating human cells, the repertoire of adducted proteins - the "adductome" - is comprised of a limited number of proteins belonging to specific functional groups, and that it is greatly enriched for histones, HMG proteins and proteins involved in RNA splicing. Treatment with low concentrations of formaldehyde caused little change in the composition of the repertoire of adducted proteins, suggesting that reactive aldehydes generated by ongoing metabolic processes may contribute to protein adduction in normally proliferating cells. The identification of an endogenous adductome highlights the importance of adduct repair in maintaining genomic structure and the potential for deficiencies in adduct repair to contribute to cancer.

Identification of novel inhibitors for the tyrosyl-DNA-phosphodiesterase 1 (Tdp1) mutant SCAN1 using virtual screening.

Spinocerebellar ataxia syndrome with axonal neuropathy (SCAN1) is a debilitating neurological disease that is caused by the mutation the Tyrosyl-DNA phosphodiesterase 1 (TDP1) DNA repair enzyme. The crucial His493 in TDP1's binding site is replaced with an arginine amino acid residue rendering the enzyme dysfunctional. A virtual screen was performed against the homology model of SCAN1 and seventeen compounds were identified and tested in a novel SCAN1 specific biochemical assay. Six compounds showed activity with IC50 values between 3.5 and 25.1 µM. The most active ligand 5 (3.5 µM) is a dicoumarin followed by a close structural analogue 6 at 6.0 µM. A less potent series of ß-carbolines (14 and 15) was found with potency in the mid-teens. According to molecular modelling an excellent fit for the active ligands into the binding pocket is predicted. To the best of our knowledge, data on inhibitors of the mutant form of TDP1 has not been reported previously. The virtual hits were also tested for wild type TDP1 activity and all six SCAN1 inhibitors are potent for the former, e.g., ligand 5 has a measured IC50 at 99 nM. In the last decade, TDP1 is considered as a promising target for adjuvant therapy against cancer in combination with Topoisomerase 1 poisons. The active ligands are mostly non-toxic to cancer cell lines A-549, T98G and MCF-7 as well as the immortalized WI-38 human fetal lung cells. Furthermore, ligands 5 and 7, show promising synergy in conjunction with topotecan, a clinically used topoisomerase 1 anticancer drug. The active ligands 5, 7, 14 and 15 have a good balance of the physicochemical properties required for oral bioavailability making the excellent candidates for further development.

Structure-Activity Relationships of Cytotoxic Lactones as Inhibitors and Mechanisms of Action.

BACKGROUND: Some lactones prevent protein Myb-dependent gene expression. OBJECTIVE: The object is to calculate inhibitors of Myb-brought genetic manifestation. METHODS: Linear quantitative structure-potency relations result expanded, among sesquiterpene lactones of a variety of macrocycles (pseudoguaianolides, guaianolides, eudesmanolides and germacranolides), to establish which part of the molecule constitutes their pharmacophore, and predict their inhibitory potency on Myb-reliant genetic manifestation, which may result helpful as leads for antileukaemic therapies with a new mechanism of action. RESULTS: Several count indices are connected with structure-activity. The α-methylene-γ-lactone ML functional groups increase, whereas OH groups decrease the activity. Hydrophobicity provides to increase cell toxicity. Four counts (ML, number of α, ß-unsaturated CO groups, etc.), connected with the number of oxygens, present a positive association, owing to the partial negative charge of oxygen. The s-trans-strans- germacranolide molecule presents maximal potency. The OH groups decrease the potency owing to the positive charge of hydrogen. The numbers of π-systems and atoms, and polarizability increase the potency. Following least squares, every standard error of the coefficients is satisfactory in every expression. The most predictive linear expressions for lactones, pseudoguaianolides and germacranolides are corroborated by leave-group-out cross-validation. Quadratic equations do not make the correlation better. CONCLUSION: Likely action mechanisms for lactones are argued with a diversity of functional groups in the lactone annulus, including artemisinin with its uncommon macrocycle characteristic, 1,2,4-trioxane cycle (pharmacophoric peroxide linkage -O1-O2- in endoperoxide ring), which results in the foundation for its sole antimalarial potency.

Structure Based Drug Design and Molecular Docking Studies of Anticancer Molecules Paclitaxel, Etoposide and Topotecan using Novel Ligands.

BACKGROUND: Tubulin is the biochemical target for several clinically used anticancer drugs as it helps in the formation of mitotic spindle during mitosis stage of cell division. Many of the anti-cancer drugs are known to interact with tubulin and microtubules including some plant alkaloids, such as paclitaxel, etoposide and topotecan. In silico drug design of these molecules were performed prior to testing these drugs in vitro. In silico drug design of these anti-cancer drugs becomes a challenge due to the complex structure of target protein. This challenge was overcome by predicting the structure of the target protein (tubulin) by homology modeling. METHODS: In this study, computer aided drug designing approach was applied to predict the suitable docking site in target protein and the interaction of tubulin protein with paclitaxel, etoposide and topotecan was explored by molecular docking using Schrödinger software. Docking score and glide energy were determined with ligands to validate their anticancer properties. RESULTS: The results indicate that etoposide is the best drug for tubulin with a docking score of - 4.916 and glide energy of -46.470 kcal/mol compared to paclitaxel and topotecan. CONCLUSION: The testing of these drugs in silico provides an alternate to in vitro testing of these molecules on cancer cell lines which is a time and cost intensive process. The in silico study of parameters, such as docking score and glide energy, will help pharmacists in developing new molecules as targets for cancers in a time and cost-effective manner.

Reversal of drug resistance by JS-K and nitric oxide in ABCB1- and ABCG2-expressing multi-drug resistant human tumor cells.

Development of resistance to chemotherapy drugs is a significant problem in treating human malignancies in the clinic. Overexpression of ABC transporter proteins, including P-170 glycoprotein (P-gp), and breast cancer resistance protein (BCRP, ABCG2) have been implicated in this multi-drug resistance (MDR). These ABC transporters are ATP-dependent efflux proteins. We have recently shown that nitric oxide (NO) inhibits the ATPase activities of P-gp, resulting in a significant enhancement of drug accumulation and the reversal of multi-drug resistance in NCI/ADR-RES cells, a P-gp-overexpressing human MDR cell line. In this study, we used [O2-(2,4-dinitrophenyl)-1-[(4-ethoxycarbonyl)-piperazin-1 yl]-diazene-1-ium-1-2-diolate] (JS-K), a tumor-specific NO-donor to study the reversal of drug resistance in both P-gp- and BCRP-overexpressing human tumor cells. We report here that while JS-K was extremely effective in reversing adriamycin resistance in the P-gp-overexpressing tumor cells (NCI/ADR-RES); it was significantly resistant to BCRP-overexpressing (MCF-7/MX) tumor cells, suggesting that JS-K may be a substrate for BCRP. Using another NO-donor (DETNO), we show that NO directly inhibits the ATP activities of BCRP, inducing significant increases in the accumulations of both Hoechst 33342 dye and topotecan, substrates for BCRP. Furthermore, NO treatment significantly reversed topotecan and mitoxantrone resistance to MCF-7/MX tumor cells. Molecular docking studies indicated that while DETNO and JS-K bind to ATP binding site in both ABC proteins, binding score was significantly reduced, compared to the ATP binding. Our results indicate that appropriately designed NO donors may find success in reversing multidrug resistance in the clinic.

Hydrogel implants for transscleral drug delivery for retinoblastoma treatment.

Retinoblastoma (Rb) is the most common primary malignant intraocular tumor in children which develops from the retinal stem cells. Systemic chemotherapy is the typical therapeutic treatment and though most children survive Rb, they often lose their vision, or the eye needs to be enucleated. Regarding to the pure availability of the target tumor by systemic chemotherapy, the local anticancer drug administration would be advantageous to increase the local drug concentration and minimize adverse side effects of chemotherapy. The present paper describes a new hydrogel implant enabled to deliver therapeutically active doses of low molecular weight hydrophilic antitumor drugs topotecan and vincristine. The hydrogel implant is proposed as bi-layered with an inner hydrophilic layer from 2-hydroxyethyl methacrylate (HEMA) serving as a reservoir of the chemotherapeutic agent and an outer hydrophobic layer from 2-ethoxyethyl methacrylate (EOEMA) acting as a barrier to protect the surrounding vascularized tissue against cytotoxicity of the delivered chemotherapeutics. The experiments with enucleated pig eyes demonstrated the ability of tested drugs to diffuse through sclera and reach the vitreous humor. HEMA-based hydrogels were examined in terms of sorption, release and transport properties, showing the possibility of adjusting the loading capacity and diffusion of the drugs by the degree of crosslinking. The EOEMA-based gels proved to be an inert for drug sorption and diffusion. A chorioallantoic membrane assay demonstrated excellent biocompatibility of unloaded hydrogels, and in vitro experiments confirmed significant cytotoxicity of drug-loaded hydrogels against a Rb cell line; 2 days for those topotecan-loaded and a minimum of 6 days for vincristine-loaded hydrogels. The bi-layered hydrogel implant can be considered promising for local administration of active agents to eye-globe for the treatment of Rb and also other ocular disorders.

Novel tyrosyl-DNA phosphodiesterase 1 inhibitors enhance the therapeutic impact of topoteсan on in vivo tumor models.

The druggability of the tyrosyl-DNA phosphodiesterase 1 (Tdp1) enzyme was investigated in conjunction with topoisomerase 1 inhibition. A novel class of thiazole, aminothiazole and hydrazonothiazole usnic acid derivatives was synthesized and evaluated as Tdp1 inhibitors and their ability to sensitize tumors to topotecan, a topoisomerase inhibitor in clinical use. Of all the compounds tested, four hydrazinothiazole derivatives, 20c, 20d, 20h and 20i, inhibited the enzyme in the nanomolar range. The activity of the compounds was verified by affinity experiments as well as supported by molecular modelling. The most effective Tdp1 inhibitor, 20d, was ton-toxic and increased the effect of topotecan both in vitro and in vivo in the Lewis lung carcinoma model. Furthermore, 20d showed significant increase in the antitumor and antimetastatic effect of topotecan in mice. The results presented here justify compound 20d to be considered as a drug lead for antitumor therapy.

Modulation of Intestinal Transport and Absorption of Topotecan, a BCRP Substrate, by Various Pharmaceutical Excipients and Their Inhibitory Mechanisms of BCRP Transporter.

Breast cancer resistance protein transporter (ABCG2/BCRP) is highly expressed on the intestinal epithelial membrane and has a significant impact on the oral absorption of topotecan. In this study, we examined 6 pharmaceutical excipients including BL-9EX, Brij97, Cremophor EL, Labrasol, Pluronic F68, and Tween 20 for their BCRP inhibitory effects. A bidirectional transport study using Caco-2 cells demonstrated that Tween 20 and Cremophor EL significantly increased the absorptive transport of topotecan, while simultaneously decreasing secretory transport. Interestingly, Labrasol selectively increased absorptive transport, whereas Pluronic F68 selectively decreased the secretory transport, of topotecan. Further investigation using an in situ closed loop experiment showed that 0.05% (w/v) Tween 20 and Cremophor EL significantly increased the intestinal absorption of topotecan in rats. An LDH assay demonstrated that 0.05% (w/v) Tween 20 and Cremophor EL did not cause significant damage to intestinal epithelial membranes. Furthermore, we examined the absorption-enhancing mechanisms of these excipients and found that Cremophor EL, Tween 20, and Labrasol increased the membrane fluidity of the inner lipid bilayers of the intestine. Therefore, this might be one of the most important mechanisms for inhibition of BCRP function by these excipients in the intestine.

Novel group of tyrosyl-DNA-phosphodiesterase 1 inhibitors based on disaccharide nucleosides as drug prototypes for anti-cancer therapy.

A new class of tyrosyl-DNA phosphodiesterase 1 (TDP1) inhibitors based on disaccharide nucleosides was identified. TDP1 plays an essential role in the resistance of cancer cells to currently used antitumour drugs based on Top1 inhibitors such as topotecan and irinotecan. The most effective inhibitors investigated in this study have IC50 values (half-maximal inhibitory concentration) in 0.4-18.5 µM range and demonstrate relatively low own cytotoxicity along with significant synergistic effect in combination with anti-cancer drug topotecan. Moreover, kinetic parameters of the enzymatic reaction and fluorescence anisotropy were measured using different types of DNA-biosensors to give a sufficient insight into the mechanism of inhibitor's action.

Pro-guest and acyclic cucurbit[n]uril conjugated polymers for the controlled release of anti-tumor drugs.

We report "pro-guest" and acyclic cucurbit[n]uril conjugated polymers as supramolecular drug delivery systems (DDSs). These supramolecular DDSs could encapsulate anti-tumor drugs. Under acidic conditions, an acid-labile "pro-guest" degraded to become a "competing guest", which displaced and released the encapsulated drug at a tunable rate.

Topotecan effect on the structure of normal and cancer plasma membrane lipid models: A multi-model approach.

Topotecan is a relatively large, planar, asymmetric and polar molecule with a lactone moiety. In neutral or basic aqueous solutions, this ring opens forming the carboxylate form of Topotecan that is biologically inactive and uncapable of passively cross membranes. Nevertheless, despite this inability to cross membranes at this form, Topotecan may still be able to interact with phospholipid bilayers, disturbing them. In this context, phospholipid models, mimicking normal (DMPC at pH 7.4) and cancer cell lipid membranes (DMPC:DMPS (5:1) at pH 6.5), were used to assess structural modifications upon interaction with Topotecan. Langmuir isotherms of monolayers coupled with Brewster angle microscopy, differential scanning calorimetry of liposomes and X-ray scattering of small and wide angle of stacked multilayers were used as complementary techniques. The overall results show that the interaction of Topotecan with lipid membranes is deeply conditioned by their composition and that Topotecan seems to have a preferential interaction with the glycerol backbone of phosphatidylcholine phospholipids.

Formulation and optimization of topotecan nanoparticles: In vitro characterization, cytotoxicity, cellular uptake and pharmacokinetic outcomes.

The study focuses on widening up the therapeutic perspective of anti-cancer therapy by entrapping a hydrophilic anticancer drug, topotecan hydrochloride (TOPO) in biodegradable poly (lactide-co-glycolide) (PLGA) matrix to form topotecan nanoparticles (TOPO NPs) by a double emulsion solvent evaporation technique. Statistical optimization using Box-Behnken design showed that sonication time of primary emulsion for 120 s, drug: polymer ratio of 1:12.65, organic phase: external aqueous phase ratio of 1:2.82 and 0.5% w/v of polyvinyl alcohol in the drug containing phase produced TOPO NPs with a size of 243.2 ±â€¯4 nm and an entrapment efficiency of 60.9 ±â€¯2.2%. TOPO NPs illustrated sustained release of TOPO for a week in phosphate buffer saline (PBS) at simulating physiological (pH 7.4) and acidic tumor microenvironmental (pH 6.5) conditions. A dramatic increase in cellular uptake with a corresponding enhanced cytotoxic potency was also displayed by TOPO NPs against human ovarian cancer cells (SKOV3) over time as compared to native drug, TOPO. These findings were further supported by the enhancement of bioavailability (13.05 fold) conferred by TOPO NPs from the in vivo pharmacokinetic study. The study represents a logistic approach for formulating TOPO NPs which can be used as an effective drug delivery system for the treatment of ovarian cancer.

Image-guided thermosensitive liposomes for focused ultrasound drug delivery: Using NIRF-labelled lipids and topotecan to visualise the effects of hyperthermia in tumours.

Image guided drug delivery using imageable thermosensitive liposomes (iTSLs) and high intensity focused ultrasound (FUS or HIFU) has attracted interest as a novel and non-invasive route to targeted delivery of anti-cancer therapeutics. FUS-induced hyperthermia is used as an externally applied "trigger" for the release of a drug cargo from within thermosensitive drug carriers. It is suggested that sub-ablative hyperthermia significantly modifies the permeability of tumour vasculature and enhances nanoparticle uptake. Here we describe the preparation and use of magnetic resonance imaging (MRI) and near infrared fluorescence (NIRF) labelled thermosensitive liposomes for imaging and tracking of biodistribution and drug release in a murine cancer model. We prepared iTSLs to encapsulate topotecan (Hycamtin®), a chemotherapeutic agent which when released in tumours can be monitored by an increase in its intrinsic drug fluorescence. FUS was applied using feedback via subcutaneously placed fine-wire thermocouples to maintain and monitor hyperthermic temperatures. iTSL accumulation was detected within tumours using NIRF imaging immediately after liposome administration. Mild FUS-induced hyperthermia (3 min at 42 °C, 30 min post i.v. administration) greatly enhanced iTSLs uptake. A co-localised enhancement of topotecan fluorescence emission was also observed immediately after application of FUS indicating rapid triggered drug release. The phenomena of increased iTSL accumulation and concomitant topotecan release appeared to be amplified by a second mild hyperthermia treatment applied one hour after the first. MRI in vivo also confirmed enhanced iTSLs uptake due to the FUS treatments. Our imaging results indicate the effects of hyperthermia on the uptake of carriers and drug. FUS-induced hyperthermia combined with real time imaging could be used as a tool for tumour targeted drug delivery.