Temperature-sensitive Liposomes Research Articles

Mathematical modelling of liposomal drug release to tumour

The primary aim of liposomal drug delivery is to wisely modulate the drug delivery system in order to target diseased tissues. Temperature-sensitive liposomes function as a prospective weapon to combat toxic side effects corresponding to direct infusion of anticancer drugs. The main objective of the present study is to model liposomal drug release, subsequent drug transport in solid tumour along with integrated actions of tumour cell surface and endosomal events. Generalized mathematical model for liposomal drug delivery is proposed in which vital physical phenomena, such as kinetics of liposome-encapsulated drug, free drug release from liposomes, transport of both liposomal drug and free drug into the tumour compartment, plasma clearance, protein-drug interactions, drug-tumour cell receptor interactions, internalization of drug through endocytosis along with corresponding endosomal events. The model is expressed through a system of coupled partial differential equations along with appropriate set of initial, interface and boundary conditions which is solved numerically. Simulated results are compared with respective existing experimental data to demonstrate the potency and reliability of the proposed model. Graphical representations of time variant concentration profiles are illustrated to understand the underlying phenomena in details. Moreover, the model speaks for the sensitivity of important drug kinetic parameters, such as advection coefficients, drug release coefficient, plasma clearance rate and internalization parameters through graphical portrayals. The proposed model and the simulated results act as a tool in designing a more effective drug delivery system for cancerous tumours.

Treatment of Primary Liver Tumors and Liver Metastases, Part 2: Non-Nuclear Medicine Techniques.

Image-guided procedures are used worldwide in the management of primary liver tumors and liver metastases. These locoregional therapies include local tumor ablation and transarterial therapies and can occasionally downstage an inoperable patient to an operable status. In hepatocellular carcinoma, data have suggested that for tumors smaller than 2 cm ablation may be preferable to surgery. Similar results are emerging for colorectal cancer liver metastases. Catheter-directed therapies such as bland embolization, transarterial chemoembolization, and drug-eluting beads represent potential techniques that can provide survival benefit for inoperable patients. In this review we highlight the most used techniques and the evidence supporting their current indications for the treatment of liver tumors. We briefly review upcoming developments in combination strategies with temperature-sensitive liposomes or immunotherapy for enhancing ablation efficacy.

Temperature-sensitive liposomes for co-delivery of tamoxifen and imatinib for synergistic breast cancer treatment

Co-delivery of chemotherapeutic agents using nanocarriers is a promising strategy for enhancing therapeutic efficacy of anticancer agents. The aim of this work was to develop tamoxifen and imatinib dual drug loaded temperature-sensitive liposomes to treat breast cancer. Liposomes were prepared using 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), monopalmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (MPPC), and different surface active agents. The liposomes were characterized for the average particle size, zeta potential, transition temperature, and drug release below and above liposomal transition temperature. The temperature-sensitive liposomes co-encapsulated with tamoxifen and imatinib were investigated for their synergistic activity against MCF-7 and MDA-MB-231 breast cancer cells. The liposomal nanoparticles showed a transition temperature of 39.4 °C and >70% encapsulation efficiency for tamoxifen and imatinib. The temperature-responsive liposomes showed more than 80% drug released within 30 min above transition temperature. Dual drug loaded liposomes showed synergistic growth inhibition against MCF-7 and MDA-MB-231 breast cancer cells. Co-delivery of tamoxifen and imatinib using temperature-sensitive liposomes can be developed as a potential targeting strategy against breast cancer.

Chemo-immunotherapy of colon cancer with focused ultrasound and Salmonella-laden temperature sensitive liposomes (thermobots)

Using attenuated Salmonella that efficiently homes in solid tumors, here we developed thermobots that actively transported membrane attached low-temperature sensitive liposome (LTSL) inside colon cancer cells for triggered doxorubicin release and simultaneous polarized macrophages to M1 phenotype with high intensity focused ultrasound (HIFU) heating (40–42 °C). Biocompatibility studies showed that the synthesized thermobots were highly efficient in LTSL loading without impacting its viability. Thermobots demonstrated efficient intracellular trafficking, high nuclear localization of doxorubicin, and induced pro-inflammatory cytokine expression in colon cancer cells in vitro. Combination of thermobots and HIFU heating (~30 min) in murine colon tumors significantly enhanced polarization of macrophages to M1 phenotype and therapeutic efficacy in vivo compared to control. Our data suggest that the thermobots and focused ultrasound treatments have the potential to improve colon cancer therapy.

In vitro Measurement of Release Kinetics of Temperature Sensitive Liposomes with a Fluorescence Imaging System.

Temperature sensitive liposomes (TSL) are a promising type of nanoparticles for localized drug delivery. TSL typically release the contained drug at mild hyperthermic temperatures (40-42 °C). Combined with localized hyperthermia, this allows for local drug delivery. In vitro characterization of TSL involves measurements of drug release at varying temperatures, but current methods are inadequate due to low temporal resolution of ~8 - 10 seconds. We present a novel method for measuring the drug release with sub-second temporal resolution. In the proposed system, the TSL entrapping the fluorescent drug (Doxorubicin) are pumped through a capillary tube. The tube is rapidly heated to a desired temperature via Peltier element. Since fluorescence increases as drug is released from TSL, drug release kinetics can be measured via fluorescent imaging. By fitting exponential models, we calculated the time constants of drug release at temperatures of 39.5, 40.5 and 41.5.C were about 6.09, 2.06 and 1.03 seconds, respectively. Our initial tests show that the developed system can measure TSL release at subsecond resolution, and thus allow adequate in vitro evaluation of TSL formulations.

Enhanced Drug Delivery to the Skin Using Liposomes.

Background:Enhancing drug delivery to the skin has importance in many therapeutic strategies. In particular, the outcome in vascularized composite allotransplantation mainly depends on systemic immunosuppression to prevent and treat episodes of transplant rejection. However, the side effects of systemic immunosuppression may introduce substantial risk to the patient and are weighed against the expected benefits. Successful enhancement of delivery of immunosuppressive agents to the most immunogenic tissues would allow for a reduction in systemic doses, thereby minimizing side effects. Nanoparticle-assisted transport by low temperature–sensitive liposomes (LTSLs) has shown some benefit in anticancer therapy. Our goal was to test whether delivery of a marker agent to the skin could be selectively enhanced.Methods:In an in vivo model, LTSLs containing doxorubicin (dox) as a marker were administered intravenously to rats that were exposed locally to mild hyperthermia. Skin samples of the hyperthermia treated hind limb were compared with skin of the contralateral normothermia hind limb. Tissue content of dox was quantified both via high-performance liquid chromatography and via histology in skin and liver.Results:The concentration of dox in hyperthermia-treated skin was significantly elevated over both normothermic skin and liver. (P < 0.02).Conclusions:We show here that delivery of therapeutics to the skin can be targeted and enhanced using LTSLs. Targeting drug delivery with this method may reduce the systemic toxicity seen in a systemic free-drug administration. Development of more hydrophilic immunosuppressants in the future would increase the applicability of this system in the treatment of rejection reactions in vascularized composite allotransplantation. The treatment of other skin condition might be another potential application.

K237-modified thermosensitive liposome enhanced the delivery efficiency and cytotoxicity of paclitaxel in vitro

This study aimed to develop novel temperature-sensitive liposomes loading paclitaxel (PTX-TSL) and evaluate them in vitro to improve the delivery efficiency and targeting of PTX. K237 peptide was conjugated to the terminal NHS of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[hydroxyl succinimidyl (polyethylene glycol)-(DSPE-PEG-NHS), and K237-modified PTX-TSL (K237-PTX-TSL) was prepared using a film dispersion method. K237-TSL encapsulation with calcein was synthesized and used to determine the cellular uptake of TSL. The morphology of K237-PTX-TSL was observed using a transmission electron microscope. The particle size and potential were measured using a laser particle size analyzer. The phase transition temperature was detected using the differential scanning calorimetry. The Cell Counting Kit-8 assay and flow cytometry were used to evaluate the effects of K237-PTX-TSL on the proliferation and cell cycle of cell lines SKOV-3 and human umbilical vein endothelial cell (HUVEC). The encapsulation efficiency of K237-PTX-TSL was 94.23% ± 0.76%. The particle diameter was 88.3 ± 4.7 nm. K237-PTX-TSL showed a fast release profile at 42 °C, while it was stable at 37 °C. PTX-TSL combined with hyperthermia significantly inhibited the cell proliferation of SKOV-3 cells and HUVECs due to increased cell arrest in the G2/M phase. The half-minimal inhibitory concentration value of K237-PTX-TSL on SKOV-3 cells and HUVECs was 13.61 ± 1.81 and 5.54 ± 0.95 nmol/L, respectively, which were significantly lower than those with PTX-TSL (p < 0.01). K237 modification could increase the targeting efficiency of TSL to cancer cells and vascular endothelial cells, thus resulting in higher cytotoxicities compared with PTX-TSL, which might be a potential formulation for targeting cancer therapy.

Formation of protein corona in vivo affects drug release from temperature-sensitive liposomes

Thermally triggered drug release from temperature-sensitive liposomes (TSL) holds great promise for cancer therapy. Different types of TSL have been designed recently for heat triggered drug release inside tumor blood vessels or after accumulation into the tumor interstitium. However, justification of drug release profiles is for far mainly based on in vitro release data. While these methods could be good enough to give early indication about the thermal sensitivity of TSL, they are still far from being optimum. This is because these methods do not take into consideration the actual adsorption of proteins onto the surface of TSL after their in vivo administration, also known as “protein corona” and the influence this could have on drug release. Therefore, in this study we compared thermal triggered drug release profile of two different types of doxorubicin encapsulated TSL; namely the lysolipid-containing TSL (LTSL) and traditional TSL (TTSL) after their in vivo recovery from the blood circulation of CD-1 mice. Ex vivo release profile at 42 °C was then tested either in the presence of full plasma or after removal of unbound plasma proteins (i.e. protein corona coated TSL). Our data showed that the influence of the environment on drug release profile was very much dependent on the type of TSL. LTSL release profile was consistently characterized by ultrafast drug release independent on the conditions tested. On the contrary, TTSL release profile changed significantly. Doxorubicin release from in vivo recovered TTSL was slow and incomplete in the presence of unbound plasma proteins, whereas very rapid drug release was detected from in vivo recovered and purified protein corona-coated TTSL in the absence of unbound proteins. Using mass spectrometry and quantification of protein adsorption, we confirmed that this discrepancy is due to the changes in protein adsorption onto TTSL when heated in the presence of unbound proteins leading to reduction in drug release. In summary this study showed that the formation of the in vivo corona on TSL will have a dramatic impact on their release profile and is dependent on both their lipid composition and the protein content of the environment in which drug release is triggered.

Temperature-sensitive liposomal ciprofloxacin for the treatment of biofilm on infected metal implants using alternating magnetic fields

Implants are commonly used as a replacement for damaged tissue. Many implants, such as pacemakers, chronic electrode implants, bone screws, and prosthetic joints, are made of or contain metal. Infections are one of the difficult to treat complications associated with metal implants due to the formation of biofilm, a thick aggregate of extracellular polymeric substances (EPS) produced by the bacteria. In this study, we treated a metal prosthesis infection model using a combination of ciprofloxacin-loaded temperature-sensitive liposomes (TSL) and alternating magnetic fields (AMF). AMF heating is used to disrupt the biofilm and release the ciprofloxacin-loaded TSL. The three main objectives of this study were to (1) investigate low- and high-temperature-sensitive liposomes (LTSLs and HTSLs) containing the antimicrobial agent ciprofloxacin for temperature-mediated antibiotic release, (2) characterise in vitro ciprofloxacin release and stability and (3) study the efficacy of combining liposomal ciprofloxacin with AMF against Pseudomonas aeruginosa biofilms grown on metal washers. The release of ciprofloxacin from LTSL and HTSL was assessed in physiological buffers. Results demonstrated a lower transition temperature for both LTSL and HTSL formulations when incubated in serum as compared with PBS, with a more pronounced impact on the HTSLs. Upon combining AMF with temperature-sensitive liposomal ciprofloxacin, a 3 log reduction in CFU of Pseudomonas aeruginosa in biofilm was observed. Our initial studies suggest that AMF exposure on metal implants can trigger release of antibiotic from temperature sensitive liposomes for a potent bactericidal effect on biofilm.

Localized delivery of therapeutic doxorubicin dose across the canine blood–brain barrier with hyperthermia and temperature sensitive liposomes

Most drugs cannot penetrate the blood–brain barrier (BBB), greatly limiting the use of anti-cancer agents for brain cancer therapy. Temperature sensitive liposomes (TSL) are nanoparticles that rapidly release the contained drug in response to hyperthermia (>40 °C). Since hyperthermia also transiently opens the BBB, we hypothesized that localized hyperthermia can achieve drug delivery across the BBB when combined with TSL. TSL-encapsulated doxorubicin (TSL-Dox) was infused intravenously over 30 min at a dose of 0.94 mg/kg in anesthetized beagles (age ∼17 months). Following, a hyperthermia probe was placed 5–10 mm deep through one of four 3-mm skull burr holes. Hyperthermia was performed randomized for 15 or 30 min, at either 45 or 50 °C. Blood was drawn every 30 min to measure TSL-Dox pharmacokinetics. Nonsurvival studies were performed in four dogs, where brain tissue at the hyperthermia location was extracted following treatment to quantify doxorubicin uptake via high-performance liquid chromatography (HPLC) and to visualize cellular uptake via fluorescence microscopy. Survival studies for 6 weeks were performed in five dogs treated by a single hyperthermia application. Local doxorubicin delivery correlated with hyperthermia duration and ranged from 0.11 to 0.74 μg/g of brain tissue at the hyperthermia locations, with undetectable drug uptake in unheated tissue. Fluorescence microscopy demonstrated doxorubicin delivery across the BBB. Histopathology in Haematoxylin & Eosin (H&E) stained samples demonstrated localized damage near the probe. No animals in the survival group demonstrated significant neurological deficits. This study demonstrates that localized doxorubicin delivery to the brain can be facilitated by TSL-Dox with localized hyperthermia with no significant neurological deficits.

Drug release kinetics of temperature sensitive liposomes measured at high-temporal resolution with a millifluidic device

Purpose: Current release assays have inadequate temporal resolution ( ∼ 10 s) to characterise temperature sensitive liposomes (TSL) designed for intravascular triggered drug release, where release within the first few seconds is relevant for drug delivery.Materials and methods: We developed a novel release assay based on a millifluidic device. A 500 µm capillary tube was heated by a temperature-controlled Peltier element. A TSL solution encapsulating a fluorescent compound was pumped through the tube, producing a fluorescence gradient along the tube due to TSL release. Release kinetics were measured by analysing fluorescence images of the tube. We measured three TSL formulations: traditional TSL (DPPC:DSPC:DSPE-PEF2000,80:15:5), MSPC-LTSL (DPPC:MSPC:DSPE-PEG2000,85:10:5) and MPPC-LTSL (DPPC:MMPC:PEF2000,86:10:4). TSL were loaded with either carboxyfluorescein (CF), Calcein, tetramethylrhodamine (TMR) or doxorubicin (Dox). TSL were diluted in one of the four buffers: phosphate buffered saline (PBS), 10% bovine serum albumin (BSA) solution, foetal bovine serum (FBS) or human plasma. Release was measured between 37–45 °C.Results: The millifluidic device allowed measurement of release kinetics within the first few seconds at ∼5 ms temporal resolution. Dox had the fastest release and highest release %, followed by CF, Calcein and TMR. Of the four buffers, release was fastest in human plasma, followed by FBS, BSA and PBS.Conclusions: The millifluidic device allows measurement of TSL release at unprecedented temporal resolution, thus allowing adequate characterisation of TSL release at time scales relevant for intravascular triggered drug release. The type of buffer and encapsulated compound significantly affect release kinetics and need to be considered when designing and evaluating novel TSL-drug combinations.

Interleaved Mapping of Temperature and Longitudinal Relaxation Rate to Monitor Drug Delivery During Magnetic Resonance-Guided High-Intensity Focused Ultrasound-Induced Hyperthermia.

Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a method to heat lesions noninvasively to a stable, elevated temperature and a well-suited method to induce local hyperthermia (41°C-43°C) in deep-seated tissues. Magnetic Resonance (MR) imaging provides therapy planning on anatomical images and offers temperature feedback based on near-real-time MR thermometry. Although constant acquisition of MR thermometry data is crucial to ensure prolonged hyperthermia, it limits the freedom to perform measurements of other MR parameters, which are of interest during hyperthermia treatments. In image-guided drug delivery applications, co-encapsulation of paramagnetic MR contrast agents with a drug inside temperature-sensitive liposomes (TSLs) allows to visualize hyperthermia-triggered drug delivery through changes of the longitudinal relaxation rate R1. While the drug accumulates in the heated tumor tissue, R1 changes can be used for an estimate of the tumor drug concentration. The main objective of this study was to demonstrate that interleaved MR sequences are able to monitor temperature with an adequate temporal resolution and could give a reasonable estimate of the achieved tumor drug concentration through R1 changes. To this aim, in vitro validation tests and an in vivo proof-of-concept study were performed. All experiments were performed on a clinical 3-T MR-HIFU system adapted with a preclinical setup. The validity of the R1 values and the temperature maps stability were evaluated in phantom experiments and in ex vivo porcine muscle tissue. In vivo experiments were performed on rats bearing a 9L glioma tumor on their hind limb. All animals (n = 4 HIFU-treated, n = 4 no HIFU) were injected intravenously with TSLs co-encapsulating doxorubicin and gadoteridol as contrast agent. The TSL injection was followed by either 2 times 15 minutes of MR-HIFU-induced hyperthermia or a sham treatment. R1 maps were acquired before, during, and after sonication, using a single slice Inversion Recovery Look-Locker (IR-LL) sequence (field of view [FOV], 50 × 69 mm; in-plane resolution, 0.52 × 0.71 mm; slice thickness, 3 mm; 23 phases of 130 milliseconds; 1 full R1 map every 2 minutes). The R1 maps acquired during treatment were interleaved with 2 perpendicular proton resonance frequency shift (PRFS) MR thermometry slices (dynamic repetition time, 8.6 seconds; FOV, 250 × 250 mm; 1.4 × 1.4 mm in-plane resolution; 4 mm slice thickness). Tumor doxorubicin concentrations were determined fluorometrically. In vitro results showed a slight but consistent overestimation of the measured R1 values compared with calibrated R1 values, regardless whether the R1 was acquired with noninterleaved IR-LL or interleaved. The average treatment cell temperature had a slightly higher temporal standard deviation for the interleaved PRFS sequence compared with the noninterleaved PRFS sequence (0.186°C vs 0.101°C, respectively). The prolonged time in between temperature maps due to the interleaved IR-LL sequence did not degrade the temperature stability during MR-HIFU treatment (Taverage = 40.9°C ± 0.3°C). Upon heat treatment, some tumors showed an R1 increase in a large part of the tumor while other tumors hardly showed any ΔR1. The tumor doxorubicin concentration showed a linear correlation with the average ΔR1 during both sonications (n = 8, Radj = 0.933), which was higher than for the ΔR1 measured after tumor cooldown (averaged for both sonications, n = 8, Radj = 0.877). The new approach of interleaving different MR sequences was applied to simultaneously acquire R1 maps and PRFS thermometry scans during a feedback-controlled MR-HIFU-induced hyperthermia treatment. Interleaved acquisition did not compromise speed or accuracy of each scan. The ΔR1 acquired during treatment was used to visualize and quantify hyperthermia-triggered release of gadoteridol from TSLs and better reflected the intratumoral doxorubicin concentrations than the ΔR1 measured after cooldown of the tumor, exemplifying the benefit of interleaving R1 maps with temperature maps during drug delivery. Our study serves as an example for interleaved MR acquisition schemes, which introduce a higher flexibility in speed, sequence optimization, and timing.

In vivo investigation of high-intensity focused ultrasound combined with thermally triggered chemotherapy for liver cancer treatment

High-Intensity Focused Ultrasound (HIFU) induces rapid tissue heating and mechanical disruption and also provides noninvasive release of chemotherapy from temperature-sensitive-liposomes (TSLs). We evaluated the combination of Sorafenib-loaded TSLs (SfTSLs) and HIFU via analysis of cell viability, tumor growth, and long-term survival. Liposomes were encapsulated with Sorafenib at 10μM with a glass transition temperature of 43°C. Hep3B human liver cancer cells were placed in PCR tubes to mimic dense tumor aggregates. Aggregates were treated with HIFU alone, SfTSLs alone, or SfTSLs + HIFU. HIFU exposure was applied for 30 seconds at acoustic output powers of 8.7 and 12W. Cell viability and proliferation were measured over 4 days post-treatment via AnnexinV/PI and WST-8 staining. Xenografted tumors were created via injection of 1.0×106 Hep3B cells within Matrigel into flanks of athymic-nude mice. Tumors at 8–10 mm were separated into the following groups: Control (sham), HIFU, SfTSLs, and SfTSLs + HIFU. Tumo...

Abstract 3108: Gemcitabine nanoparticles show in vitro efficacy in murine pancreatic ductal adenocarcinoma

Abstract Our goal is to develop nanotherapeutics for the treatment of pancreatic ductal adenocarcinoma (PC). Squalenoylated Gem (SqGemNPs) and Gem-loaded temperature sensitive liposomes (GemTSLs) were synthesized and the resulting efficacy was compared to that of gemcitabine (Gem) and Abraxane®. Squalenoylation is the conjugation of squalene, a cholesterol precursor, to a drug and enhances in vivo delivery, half-life, and therapeutic efficacy [1]. All particles were evaluated in vitro in both a monolayer and organoid culture of the KrasLSL-G12D/+; Trp53LSL-R172H/+; Pdx-Cre (KPC) model. The organoid culture allows for phenotypic maintenance that is otherwise lost with monolayer culturing [2]. SqGem and Cholesterol-PEG2k co-assembled into SqGemNPs via nanoprecipitation to yield particles of 210 ± 150 nm with 35 wt% Gem. Gem was loaded into TSLs by complexing copper to Gem inside multilamellar liposomes comprised of DPPC:DSPE-PEG2K:DSPC (50:5:15) to yield particles of 110 ± 26 nm with 1.7 wt% Gem. KPC cells were plated as both monolayers and Matrigel™ suspensions and organoid-cultured cells were plated in Matrigel. Cells were incubated with free Gem, SqGemNPs, pre-heated Gem-TSLs, or Abraxane. At 48h, cell survival was assessed using an MTT assay (Invitrogen, Carlsbad, CA). In monolayer-cultured cells, SqGemNPs was the only tested therapeutic to achieve 100% cell death (which occurred at a concentration of 50 uM). All other treatments reached a plateau of efficacy as a function of concentration. Two anticipated trends were confirmed; monolayer-cultured cells were more responsive to all treatments than organoid-cultured cells, and cells plated in Matrigel were less responsive to therapy than those plated as a monolayer. We found that the efficacy of preheated GemTSLs was similar to free Gem in all cell cultures and thus release from the TSLs was validated. In the organoid culture, the IC50 of SqGemNPs was 0.12 ± 0.04 uM compared to 0.19 ± 0.04 uM for free Gem, although both reached a plateau of efficacy at 70% cell death. The efficacy of Abraxane, GemTSLs and Gem plateaued at 45%, 77% and 70% cell death, respectively in organoids. In future studies, two techniques to increase drug availability in PC tumors will be evaluated: SqGemNPs plus high intensity ultrasound ablation, which can increase drug accumulation by 50-fold [3] and GemTSLs plus ultrasound hyperthermia to locally release Gem at a high concentration within the tumor vasculature. 1 Couvreur, P. et al. Nano Lett 6, 2544-2548, doi:10.1021/nl061942q (2006). 2 Boj, S. F. et al. Cell 160, 324-338, doi:10.1016/j.cell.2014.12.021 (2015). 3 Wong, A. W. et al. J Clin Invest 126, 99-111, doi:10.1172/Jci83312 (2016). Citation Format: Samantha T. Tucci, Hamilton Kakwere, Azadeh Kheirolomoom, Jai W. Seo, Elizabeth Ingham, Chang-Il Hwang, Katherine Ferrara. Gemcitabine nanoparticles show in vitro efficacy in murine pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3108. doi:10.1158/1538-7445.AM2017-3108

Engineering of multifunctional temperature-sensitive liposomes for synergistic photothermal, photodynamic, and chemotherapeutic effects

Heterogeneity of cancer cells and drug resistance require multiple therapeutic approaches for comprehensive treatment. In this study, temperature-sensitive liposomes containing anti-cancer agent tanespimycin (17-AAG) and photosensitizer IR 820 were developed for combination of phototherapy and chemotherapy. The temperature-sensitive liposomes composed of DPPC, cholesterol, DSPE-PEG, 17-AAG, and IR 820 (LP-AI) at weight ratio of 35/15/3/2/2 were formulated as a thin film using extrusion and evaluated for particle size, morphology and drug release profile. Furthermore, the anticancer effect of combined therapy was examined in vitro and in vivo in SCC-7 and MCF-7 cell lines. As a result, LP-AI was prepared at particle size of 166.7±1.3nm, PDI of 0.153±0.012, and ζ-potential of −32.6±0.8mV. After NIR irradiation (660 and 808nm laser), LP-AI could generate heat and ROS and enhance drug release from nanoparticles which were useful to kill the cancer cells. These were confirmed by in vitro cytotoxicity as well as in vivo effective ablation of tumors. In conclusion, fast drug release and enhanced treatment efficacy of LP-AI indicate the potential of integrating photo- and chemotherapy for synergistic anti-cancer effects.

Temperature sensitive liposomes combined with thermal ablation: Effects of duration and timing of heating in mathematical models and in vivo.

BackgroundTemperature sensitive liposomes (TSL) are nanoparticles that rapidly release the contained drug at hyperthermic temperatures, typically above ~40°C. TSL have been combined with various heating modalities, but there is no consensus on required hyperthermia duration or ideal timing of heating relative to TSL administration. The goal of this study was to determine changes in drug uptake when heating duration and timing are varied when combining TSL with radiofrequency ablation (RF) heating.MethodsWe used computer models to simulate both RF tissue heating and TSL drug delivery, to calculate spatial drug concentration maps. We simulated heating for 5, 12 and 30 min for a single RF electrode, as well as three sequential 12 min ablations for 3 electrodes placed in a triangular array. To support simulation results, we performed porcine in vivo studies in normal liver, where TSL filled with doxorubicin (TSL-Dox) at a dose of 30 mg was infused over 30 min. Following infusion, RF heating was performed in separate liver locations for either 5 min (n = 2) or 12 min (n = 2). After ablation, the animal was euthanized, and liver extracted and frozen. Liver samples were cut orthogonal to the electrode axis, and fluorescence imaging was used to visualize tissue doxorubicin distribution.ResultsBoth in vivo studies and computer models demonstrate a ring-shaped drug deposition within ~1 cm of the visibly coagulated tissue. Drug uptake directly correlated with heating duration. In computer simulations, drug concentration increased by a factor of 2.2x and 4.3x when heating duration was extended from 5 to either 12, or 30 minutes, respectively. In vivo, drug concentration was by a factor of 2.4x higher at 12 vs 5 min heating duration (7.1 μg/g to 3.0 μg/g). The computer models suggest that heating should be timed to maximize area under the curve of systemic plasma concentration of encapsulated drug.ConclusionsBoth computer models and in vivo study demonstrate that tissue drug uptake directly correlates with heating duration for TSL based delivery. Computational models were able to predict the spatial drug delivery profile, and may serve as a valuable tool in understanding and optimizing drug delivery systems.

Thermal combination therapies for local drug delivery by magnetic resonance-guided high-intensity focused ultrasound

Several thermal-therapy strategies such as thermal ablation, hyperthermia-triggered drug delivery from temperature-sensitive liposomes (TSLs), and combinations of the above were investigated in a rhabdomyosarcoma rat tumor model (n = 113). Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) was used as a noninvasive heating device with precise temperature control for image-guided drug delivery. For the latter, TSLs were prepared, coencapsulating doxorubicin (dox) and [Gd(HPDO3A)(H2O)], and injected in tumor-bearing rats before MR-HIFU treatment. Four treatment groups were defined: hyperthermia, ablation, hyperthermia followed by ablation, or no HIFU. The intratumoral TSL and dox distribution were analyzed by single-photon emission computed tomography (SPECT)/computed tomography (CT), autoradiography, and fluorescence microscopy. Dox biodistribution was quantified and compared with that of nonliposomal dox. Finally, the treatment efficacy of all heating strategies plus additional control groups (saline, free dox, and Caelyx) was assessed by tumor growth measurements. All HIFU heating strategies combined with TSLs resulted in cellular uptake of dox deep into the interstitial space and a significant increase of tumor drug concentrations compared with a treatment with free dox. Ablation after TSL injection showed [Gd(HPDO3A)(H2O)] and dox release along the tumor rim, mirroring the TSL distribution pattern. Hyperthermia either as standalone treatment or before ablation ensured homogeneous TSL, [Gd(HPDO3A)(H2O)], and dox delivery across the tumor. The combination of hyperthermia-triggered drug delivery followed by ablation showed the best therapeutic outcome compared with all other treatment groups due to direct induction of thermal necrosis in the tumor core and efficient drug delivery to the tumor rim.

Dynamic contrast enhanced MRI detects changes in vascular transport rate constants following treatment with thermally-sensitive liposomal doxorubicin

Temperature-sensitive liposomal formulations of chemotherapeutics, such as doxorubicin, can achieve locally high drug concentrations within a tumor and tumor vasculature while maintaining low systemic toxicity. Further, doxorubicin delivery by temperature-sensitive liposomes can reliably cure local cancer in mouse models. Histological sections of treated tumors have detected red blood cell extravasation within tumors treated with temperature-sensitive doxorubicin and ultrasound hyperthermia. We hypothesize that the local release of drug into the tumor vasculature and resulting high drug concentration can alter vascular transport rate constants along with having direct tumoricidal effects. Dynamic contrast enhanced MRI (DCE-MRI) coupled with a pharmacokinetic model can detect and quantify changes in such vascular transport rate constants. Here, we set out to determine whether changes in rate constants resulting from intravascular drug release were detectable by MRI. We found that the accumulation of gadoteridol was enhanced in tumors treated with temperature-sensitive liposomal doxorubicin and ultrasound hyperthermia. While the initial uptake rate of the small molecule tracer was slower (k1=0.0478±0.011s−1 versus 0.116±0.047s−1) in treated compared to untreated tumors, the tracer was retained after treatment due to a larger reduction in the rate of clearance (k2=0.291±0.030s−1 versus 0.747±0.24s−1). While DCE-MRI assesses a combination of blood flow and permeability, ultrasound imaging of microvascular flow rate is sensitive only to changes in vascular flow rate; based on this technique, blood flow was not significantly altered 30min after treatment. In summary, DCE-MRI provides a means to detect changes that are associated with treatment by thermally-activated particles and such changes can be exploited to enhance local delivery.

Programmed Multiresponsive Vesicles for Enhanced Tumor Penetration and Combination Therapy of Triple‐Negative Breast Cancer

Nanomedicine is a promising approach for combination chemotherapy of triple‐negative breast cancer (TNBC). However, the therapeutic efficacy of nanoparticulate drugs is suppressed by a series of biological barriers. The authors herein present a programmed stimuli‐responsive liposomal vesicle to overcome the sequential barriers for enhanced TNBC therapy. The intelligent vesicles are engineered by integrating an enzyme‐cleavable polyethylene glycol (PEG) corona, a light‐responsive photosensitizer pheophorbide a (PPa), and a temperature‐sensitive liposome (TSL) into a single nanoplatform. The resultant enzyme, light, and temperature multisensitive liposome (ELTSL) is sequentially coloaded with a lipophilic oxaliplatin prodrug of hexadecyl‐oxaliplatin carboxylic acid (HOC) and hydrophilic doxorubicin hydrochloride (DOX). Dual drug‐loaded ELTSL displays enhanced tumor penetration and increased cellular uptake upon matrix metalloproteinase 2 mediated cleavage of the PEG corona. Under NIR laser irradiation, PPa induces mild hyperthermia effect to trigger ultrafast drug release in the tumor cells. In combination with PPa‐mediated photodynamic therapy, HOC and DOX coloaded ELTSL show significantly improved antitumor efficacy than monotherapy. Given the clinically translatable potential of the liposomal vesicles, ELTSL might represent a promising nanoplatform for combination TNBC therapy.

Advancements in intelligent drug delivery systems and their clinical applications

Background: Intelligent Drug Delivery Systems (DDSs) have revolutionized the way medications are administered, aiming to enhance therapeutic efficacy while minimizing side effects. Conventional DDSs often lead to systemic drug distribution and uncontrolled release, causing undesirable side effects and suboptimal therapeutic outcomes. To address these limitations, advanced controlled DDSs, particularly those leveraging nanotechnology, have been developed to target specific sites with precise regulation. Aim: This review aims to explore the recent advancements in intelligent drug delivery systems, focusing on their design, mechanisms, and clinical applications. It highlights the role of nanotechnology in enhancing the specificity and efficacy of drug delivery through various stimuli-responsive mechanisms. Methods: The review synthesizes findings from recent studies on various smart drug delivery platforms, including nanoparticle-based systems, smart polymers, liposomes, and organic-inorganic hybrids. It evaluates these systems based on their responsiveness to internal stimuli (e.g., pH, redox reactions, enzymes) and external stimuli (e.g., temperature, light, magnetic fields), and their clinical applicability. Results: The review identifies several innovative DDSs that employ stimuli-responsive materials to control drug release. Notable advancements include pH-responsive nanoparticles targeting tumor cells, redox-responsive systems for cancer therapy, and temperature-sensitive liposomes used in hyperthermia.