Mild hyperthermia triggered doxorubicin release from optimized stealth thermosensitive liposomes improves intratumoral drug delivery and efficacy

Augmentation of the EPR effect by mild hyperthermia to improve nanoparticle delivery to the tumor

The clinical translation of the nanoparticle (NP)-based anticancer therapies is still unsatisfactory due to the heterogeneity of the enhanced permeability and retention (EPR) effect. Despite the promising preclinical outcome of the pharmacological EPR enhancers, their systemic toxicity can limit their clinical application. Hyperthermia (HT) presents an efficient tool to augment the EPR by improving tumor blood flow (TBF) and vascular permeability, lowering interstitial fluid pressure (IFP), and disrupting the structure of the extracellular matrix (ECM). Furthermore, the HT-triggered intravascular release approach can overcome the EPR effect. In contrast to pharmacological approaches, HT is safe and can be focused to cancer tissues. Moreover, HT conveys direct anti-cancer effects, which improve the efficacy of the anti-cancer agents encapsulated in NPs. However, the clinical application of HT is challenging due to the heterogeneous distribution of temperature within the tumor, the length of the treatment and the complexity of monitoring.

Mild Hyperthermia Enhanced Liposomal Doxorubicin Delivery and CD8+ T cell Infiltration in Triple Negative Breast Cancer

Mild hyperthermia (MHTh) is often used in combination with chemotherapy and radiotherapy for cancer treatment. In the current study, the effect of MHTh on the enhanced uptake of the FDA-approved chemotherapy drug, liposomal doxorubicin (dox) in syngeneic 4T1 tumors was investigated. Doxorubicin has inherent fluorescence properties having an emission signal at 590 nm upon excitation with a 480 nm laser. A group of mice administered with doxorubicin (dox) were exposed to MHTh (42 °C) for 30 minutes whereas control group given dox did not receive MHTh. Ex vivo optical imaging of harvested tumors confirmed higher uptake of dox in treated versus the control untreated tumors. Confocal microscopy of tumor sections indicates higher fluorescent intensity due to increased accumulation of dox in MHTh-treated compared to untreated tumors. We examined the effect of MHTh to enhance CD8 tumor infiltration, production of interferon-γ (IFN-γ) and expression of programmed death ligand-1 (PD-L1). mRNA in situ hybridization was performed to test for transcripts of CD8, IFN-γ and PD-L1. Results showed that higher expression of CD8 mRNA was observed in MHTh-administered tumors versus untreated cohorts. The signal for IFN-γ and PD-L1 in both groups were not significantly different. Taken together, our findings imply that MHTh can improve tumor uptake of dox. Importantly, our data suggests that MHTh can boost CD8+ T cell infiltration.

Combination Treatment with Liposomal Doxorubicin and Inductive Moderate Hyperthermia for Sarcoma Saos-2 Cells

Despite efforts in osteosarcoma (OS) research, the role of inductive moderate hyperthermia (IMH) in delivering and enhancing the antitumor effect of liposomal doxorubicin formulations (LDOX) remains unresolved. This study investigated the effect of a combination treatment with LDOX and IMH on Saos-2 human OS cells. We compared cell viability using a trypan blue assay, apoptosis and reactive oxygen species (ROS) measured by flow cytometry and pro-apoptotic Bax protein expression examined by immunocytochemistry in response to IMH (42 MHz frequency, 15 W power for 30 min), LDOX (0.4 μg/mL), and LDOX plus IMH. The lower IC50 value of LDOX at 72 h indicated increased accumulation of the drug in the OS cells. LDOX plus IMH resulted in a 61% lower cell viability compared to no treatment. Moreover, IMH potentiated the LDOX action on the Saos-2 cells by promoting ROS production at temperatures of <42 °C. There was a 12% increase in cell populations undergoing early apoptosis with a less heterogeneous distribution of Bax after combination treatment compared to those treated with LDOX (p < 0.05). Therefore, we determined that IMH could enhance LDOX delivery and its antitumor effect via altered membrane permeabilization, ROS generation, and a lower level of visualized Bax heterogeneity in the Saos-2 cells, suggesting the potential translation of these findings into in vivo studies.

Perturbation of Copper Homeostasis Sensitizes Cancer Cells to Elevated Temperature

Temporary elevation of tumor temperature, also known as hyperthermia, is a safe and well-tolerated treatment modality. The efficacy of hyperthermia can be improved by efficient thermosensitizers, and various candidate drugs, including inhibitors of the heat stress response, have been explored in vitro and in animal models, but clinically relevant thermosensitizers are lacking. Here, we employ unbiased in silico approaches to uncover new mechanisms and compounds that could be leveraged to increase the thermosensitivity of cancer cells. We then focus on elesclomol, a well-performing compound, which amplifies cell killing by hyperthermia by 5- to 20-fold in cell lines and outperforms clinically applied chemotherapy when combined with hyperthermia in vitro. Surprisingly, our findings suggest that the thermosensitizing effects of elesclomol are independent of its previously reported modes of action but depend on copper shuttling. Importantly, we show that, like elesclomol, multiple other copper shuttlers can thermosensitize, suggesting that disturbing copper homeostasis could be a general strategy for improving the efficacy of hyperthermia.

Doxorubicin and other anthracyclines in cancers: Activity, chemoresistance and its overcoming

Anthracyclines have been important and effective treatments against a number of cancers since their discovery. However, their use in therapy has been complicated by severe side effects and toxicity that occur during or after treatment, including cardiotoxicity. The mode of action of anthracyclines is complex, with several mechanisms proposed. It is possible that their high toxicity is due to the large set of processes involved in anthracycline action. The development of resistance is a major barrier to successful treatment when using anthracyclines. This resistance is based on a series of mechanisms that have been studied and addressed in recent years. This work provides an overview of the anthracyclines used in cancer therapy. It discusses their mechanisms of activity, toxicity, and chemoresistance, as well as the approaches used to improve their activity, decrease their toxicity, and overcome resistance.

Box-Behnken design of thermo-responsive nano-liposomes loaded with a platinum(iv) anticancer complex: evaluation of cytotoxicity and apoptotic pathways in triple negative breast cancer cells

Herein, thermo-responsive liposomes (TLs) loaded with Asp (Asp/TLs) were produced by self-assembling DPPC, DSPE-PEG2000, and cholesterol. The preparation variables were optimized using the Box-Behnken design (BBD). The optimized Asp/TLs exhibited an average particle size of 114.05 ± 1.56 nm, PDI of 0.15 ± 0.015, zeta potential of -15.24 ± 0.65 mV, and entrapment efficiency (EE%) of 84.08 ± 2.75%. In addition, under physiological conditions, Asp/TLs showed spherical shape, outstanding stability and thermo-triggered the release of Asp at 38 °C, reaching the maximum Asp release at 40 °C. The MTT assay showed that the optimal Asp/TLs exhibited the highest cytotoxic activity upon exposure to mild hyperthermia (40 °C) against the invasive triple-negative breast cancer cell line (MDA-MB-231) when compared to other preparations. The IC50 of Asp/TLs (40 °C) was estimated at 0.9 μg mL-1, while that of free Asp (40 °C) was 3.83 μg mL-1. As such, the optimal Asp/TLs were shown to increase the cytotoxic activity of Asp by 4-fold upon exposure to mild hyperthermia. The IC50 values of Asp and Asp/TLs without exposure to 40 °C were 6.6 μg mL-1 and 186 μg mL-1, respectively. This indicated that Asp was released only when placed at 40 °C. The apoptosis assay revealed that Asp/TLs (40 °C) caused a remarkable increase in the percentage of cell population among both the late apoptosis and necrosis quartiles, as well as a significant decline in the viable cell quartile (P ≤ 0.001) when compared to Asp (40 °C). Asp/TLs (40 °C) and Asp (40 °C) could stimulate the intrinsic apoptosis pathway by upregulating the apoptotic genes Bak and Bax, while downregulating the anti-apoptotic genes, BCL-xL and BCL-2. The free Asp (40 °C) increased the gene expression of Bak and Bax by 4.4- and 5.2-folds, while reducing the expression of BCL-xL and BCL-2 by 50% and 73%, respectively. The optimal Asp TLs (40 °C) manifested more potent effects as demonstrated by the upregulation of Bak, Bax, and P53 by 5.6-, 7.2-, and 1.3-folds, as well as the downregulation of BCL-xL and BCL-2 by 70% and 85%, respectively. As such, the optimal Asp TLs (40 °C) treatment displayed the most potent cytotoxic profile and induced both apoptosis and necrosis in MDA-MB-231.

In Vivo Detection of Circulating Cancer-Associated Fibroblasts in Breast Tumor Mouse Xenograft: Impact of Tumor Stroma and Chemotherapy

Cancer-associated fibroblasts (CAFs) are important drivers in the tumor microenvironment and facilitate the growth and survival of tumor cells, as well as metastasis formation. They may travel together with tumor cells to support their survival and aid in the formation of a metastatic niche. In this study, we aimed to study circulating CAFs (cCAFs) and circulating tumor cells (CTCs) in a preclinical breast tumor model in mice in order to understand the effect of chemotherapy on cCAFs and CTC formation. Tumors with MDA-MB-231 human breast tumor cells with/without primary human mammary fibroblasts (representing CAFs) were coinjected in SCID mice to develop tumors. We found that the tumors with CAFs grew faster than tumors without CAFs. To study the effect of the stroma on CTCs and cCAFs, we isolated cells using microsieve filtration technology and established ITGA5 as a new cCAF biomarker, which showed good agreement with the CAF markers FAP and α-SMA. We found that ITGA5+ cCAFs shed in the blood of mice bearing stroma-rich coinjection-based tumors, while there was no difference in CTC formation. Although treatment with liposomal doxorubicin reduced tumor growth, it increased the numbers of both cCAFs and CTCs in blood. Moreover, cCAFs and CTCs were found to form clusters in the chemotherapy-treated mice. Altogether, these findings indicate that the tumor stroma supports tumor growth and the formation of cCAFs. Furthermore, chemotherapy may exacerbate the formation of cCAFs and CTCs, which may eventually support the formation of a metastasis niche in breast cancer.

Responsive Nanostructure for Targeted Drug Delivery

Currently, intelligent, responsive biomaterials have been widely explored, considering the fact that responsive biomaterials provide controlled and predictable results in various biomedical systems. Responsive nanostructures undergo reversible or irreversible changes in the presence of a stimulus, and that stimuli can be temperature, a magnetic field, ultrasound, pH, humidity, pressure, light, electric field, etc. Different types of stimuli being used in drug delivery shall be explained here. Recent research progress in the design, development and applications of biomaterials comprising responsive nanostructures is also described here. More emphasis will be given on the various nanostructures explored for the smart stimuli responsive drug delivery at the target site such as wound healing, cancer therapy, inflammation, and pain management in order to achieve the improved efficacy and sustainability with the lowest side effects. However, it is still a big challenge to develop well-defined responsive nanostructures with ordered output; thus, challenges faced during the design and development of these nanostructures shall also be included in this article. Clinical perspectives and applicability of the responsive nanostructures in the targeted drug delivery shall be discussed here.

CXCL10-coronated thermosensitive "stealth" liposomes for sequential chemoimmunotherapy in melanoma

The interplay of liposome-protein corona hinders the clinical application of liposomes due to active macrophage sequestration and rapid plasma clearance. Here we showed that, CXCL10 as a therapeutic protein was coronated the thermosensitive liposomes to form stealth-like nanocarriers (CXCL10/TSLs). Decoration of the corona layer of CXCL10/TSLs by hyaluronic acid conjugated oridonin (ORD/CXCL10/TSLs), overcame the "fluid barrier" built by biological proteins, drastically reduced capture by leukocytes in whole blood, allowed the specific targeting of tumor sites. Multifunctional medicine ORD/CXCL10/TSLs with hyperthermia drove the sustained cytokine-CXCL10 inflammatory loop to switch macrophage phenotype to M1-like, expand tumor-infiltrating natural killer cells and induce intratumoral levels of interferon-γ. Oridonin synergized with CXCL10 during ORD/CXCL10/TSLs treatment, downregulated PI3K/AKT and Raf/MEK signaling for M1-like polarization and migration inhibition. Furthermore, ORD/CXCL10/TSLs potently synergized with anti-PD-L1 antibody in mice bearing metastatic melanoma, induced sustained immunological memory and controlled metastatic spread.

Review of the Delivery Kinetics of Thermosensitive Liposomes

Thermosensitive liposomes (TSL) are triggered nanoparticles that release the encapsulated drug in response to hyperthermia. Combined with localized hyperthermia, TSL enabled loco-regional drug delivery to tumors with reduced systemic toxicities. More recent TSL formulations are based on intravascular triggered release, where drug release occurs within the microvasculature. Thus, this delivery strategy does not require enhanced permeability and retention (EPR). Compared to traditional nanoparticle drug delivery systems based on EPR with passive or active tumor targeting (typically <5%ID/g tumor), TSL can achieve superior tumor drug uptake (>10%ID/g tumor). Numerous TSL formulations have been combined with various drugs and hyperthermia devices in preclinical and clinical studies over the last four decades. Here, we review how the properties of TSL dictate delivery and discuss the advantages of rapid drug release from TSL. We show the benefits of selecting a drug with rapid extraction by tissue, and with quick cellular uptake. Furthermore, the optimal characteristics of hyperthermia devices are reviewed, and impact of tumor biology and cancer cell characteristics are discussed. Thus, this review provides guidelines on how to improve drug delivery with TSL by optimizing the combination of TSL, drug, and hyperthermia method. Many of the concepts discussed are applicable to a variety of other triggered drug delivery systems.

Image-guided drug delivery in nanosystem-based cancer therapies

The past decades have shown significant advancements in the development of solid tumor treatment. For instance, implementation of nanosystems for drug delivery has led to a reduction in side effects and improved delivery to the tumor region. However, clinical translation has faced challenges, as tumor drug levels are still considered to be inadequate. Interdisciplinary research has resulted in the development of more advanced drug delivery systems. These are coined "smart" due to the ability to be followed and actively manipulated in order to have better control over local drug release. Therefore, image-guided drug delivery can be a powerful strategy to improve drug activity at the target site. Being able to visualize the inflow of the administered smart nanosystem within the tumor gives the potential to determine the right moment to apply the facilitator to initiate drug release. Here we provide an overview of available nanosystems, imaging moieties, and imaging techniques. We discuss preclinical application of these smart drug delivery systems, the strength of image-guided drug delivery, and the future of personalized treatment.

Enhanced tumor penetration for efficient chemotherapy by a magnetothermally sensitive micelle combined with magnetic targeting and magnetic hyperthermia

The high accumulation and poor penetration of nanocarriers in tumor is a contradiction of nanomedicine, which reduces the efficacy of chemotherapy. Due to the positive effect of hyperthermia on in vivo drug diffusion, we designed a magnetothermally sensitive micelle (MTM) by integrating magnetic targeting (MT), magnetic hyperthermia (MH), and magnetothermally responsive drug release to facilitate simultaneous drug accumulation and penetration in tumor. Accordingly, we synthesized a cyanine7-modified thermosensitive polymer with phase transition at 42.3°C, and utilized it to prepare drug-loaded MTMs by encapsulating superparamagnetic MnFe2O4 nanoparticles and doxorubicin (DOX). The obtained DOX–MTM had not only high contents of DOX (9.1%) and MnFe2O4 (38.7%), but also some advantages such as superparamagnetism, high saturation magnetization, excellent magnetocaloric effect, and magnetothermal-dependent drug release. Therefore, DOX–MTM improved in vitro DOX cytotoxicity by enhancing DOX endocytosis under the assistance of MH. Furthermore, MT and MH enhanced in vivo DOX–MTM accumulation and DOX penetration in tumor, respectively, substantially inhibiting tumor growth (84%) with excellent biosafety. These results indicate the development of an optimized drug delivery system with MH and MH-dependent drug release, introducing a feasible strategy to enhance the application of nanomedicines in tumor chemotherapy.

Cardiolipin for Enhanced Cellular Uptake and Cytotoxicity of Thermosensitive Liposome-Encapsulated Daunorubicin toward Breast Cancer Cell Lines

Daunorubicin (DNR) and cardiolipin (CL) were co-delivered using thermosensitive liposomes (TSLs). 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1-myristoyl-2-stearoyl-sn-glycero-3-phosphocholine (MSPC), cholesterol, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] or DSPE-mPEG (2000) and CL were used in the formulation of liposomes at a molar ratio of 57:40:30:3:20, respectively. CL forms raft-like microdomains that may relocate and change lipid organization of the outer and inner mitochondrial membranes. Such transbilayer lipid movement eventually leads to membrane permeabilization. TSLs were prepared by thin-film hydration (drug:lipid ratio 1:5) where DNR was encapsulated within the aqueous core of the liposomes and CL acted as a component of the lipid bilayer. The liposomes exhibited high drug encapsulation efficiency (>90%), small size (~115 nm), narrow size distribution (polydispersity index ~0.12), and a rapid release profile under the influence of mild hyperthermia. The liposomes also exhibited ~4-fold higher cytotoxicity against MDA-MB-231 cells compared to DNR or liposomes similar to DaunoXome® (p < 0.001). This study provides a basis for developing a co-delivery system of DNR and CL encapsulated in liposomes for treatment of breast cancer.

Vesicular and Planar Membranes of Archaea Lipids: Unusual Physical Properties and Biomedical Applications

Liposomes and planar membranes made of archaea or archaea-like lipids exhibit many unusual physical properties compared to model membranes composed of conventional diester lipids. Here, we review several recent findings in this research area, which include (1) thermosensitive archaeosomes with the capability to drastically change the membrane surface charge, (2) MthK channel's capability to insert into tightly packed tetraether black lipid membranes and exhibit channel activity with surprisingly high calcium sensitivity, and (3) the intercalation of apolar squalane into the midplane space of diether bilayers to impede proton permeation. We also review the usage of tetraether archaeosomes as nanocarriers of therapeutics and vaccine adjuvants, as well as the biomedical applications of planar archaea lipid membranes. The discussion on archaeosomal therapeutics is focused on partially purified tetraether lipid fractions such as the polar lipid fraction E (PLFE) and glyceryl caldityl tetraether (GCTE), which are the main components of PLFE with the sugar and phosphate removed.

Feasibility of ultrasound tomography-guided localized mild hyperthermia using a ring transducer: Ex vivo and in silico studies

BACKGROUND

As of 2022, breast cancer continues to be the most diagnosed cancer worldwide. This problem persists within the United States as well, as the American Cancer Society has reported that ∼12.5% of women will be diagnosed with invasive breast cancer over the course of their lifetime. Therefore, a clinical need continues to exist to address this disease from a treatment and therapeutic perspective. Current treatments for breast cancer and cancers more broadly include surgery, radiation, and chemotherapy. Adjuncts to these methods have been developed to improve the clinical outcomes for patients. One such adjunctive treatment is mild hyperthermia therapy (MHTh), which has been shown to be successful in the treatment of cancers by increasing effectiveness and reduced dosage requirements for radiation and chemotherapies. MHTh-assisted treatments can be performed with invasive thermal devices, noninvasive microwave induction, heating and recirculation of extracted patient blood, or whole-body hyperthermia with hot blankets.

PURPOSE

One common method for inducing MHTh is by using microwave for heat induction and magnetic resonance imaging for temperature monitoring. However, this leads to a complex, expensive, and inaccessible therapy platform. Therefore, in this work we aim to show the feasibility of a novel all-acoustic MHTh system that uses focused ultrasound (US) to induce heating while also using US tomography (UST) to provide temperature estimates. Changes in sound speed (SS) have been shown to be strongly correlated with temperature changes and can therefore be used to indirectly monitor heating throughout the therapy. Additionally, these SS estimates allow for heterogeneous SS-corrected phase delays when heating complex and heterogeneous tissue structures.

METHODS

Feasibility to induce localized heat in tissue was investigated in silico with a simulated breast model, including an embedded tumor using continuous wave US. Here, both heterogenous acoustic and thermal properties were modeled in addition to blood perfusion. We further demonstrate, with ex vivo tissue phantoms, the feasibility of using ring-based UST to monitor temperature by tracking changes in SS. Two phantoms (lamb tissue and human abdominal fat) with latex tubes containing varied temperature flowing water were imaged. The measured SS of the water at each temperature were compared against values that are reported in literature.

RESULTS

Results from ex vivo tissue studies indicate successful tracking of temperature under various phantom configurations and ranges of water temperature. The results of in silico studies show that the proposed system can heat an acoustically and thermally heterogenous breast model to the clinically relevant temperature of 42°C while accounting for a reasonable time needed to image the current cross section (200 ms). Further, we have performed an initial in silico study demonstrating the feasibility of adjusting the transmit waveform frequency to modify the effective heating height at the focused region. Lastly, we have shown in a simpler 2D breast model that MHTh level temperatures can be maintained by adjusting the transmit pressure intensity of the US ring.

CONCLUSIONS

This work has demonstrated the feasibility of using a 256-element ring array transducer for temperature monitoring; however, future work will investigate minimizing the difference between measured SS and the values shown in literature. A hypothesis attributes this bias to potential volumetric average artifacts from the ray-based SS inversion algorithm that was used, and that moving to a waveform-based SS inversion algorithm will greatly improve the SS estimates. Additionally, we have shown that an all-acoustic MHTh system is feasible via in silico studies. These studies have indicated that the proposed system can heat a tumor within a heterogenous breast model to 42°C within a narrow time frame. This holds great promise for increasing the accessibility and reducing the complexity of a future all-acoustic MHTh system.

Extracorporeal Removal of Thermosensitive Liposomal Doxorubicin from Systemic Circulation after Tumor Delivery to Reduce Toxicities

Thermosensitive liposomal doxorubicin (TSL-Dox) combined with localized hyperthermia enables targeted drug delivery. Tumor drug uptake occurs only during hyperthermia. We developed a novel method for removal of systemic TSL-Dox remaining after hyperthermia-triggered delivery to reduce toxicities. The carotid artery and jugular vein of Norway brown rats carrying two subcutaneous BN-175 tumors were catheterized. After allowing the animals to recover, TSL-Dox was infused at 7 mg/kg dose. Drug delivery to one of the tumors was performed by inducing 15 min microwave hyperthermia (43 °C). At the end of hyperthermia, an extracorporeal circuit (ECC) comprising a heating module to release drug from TSL-Dox followed by an activated carbon filter to remove free drug was established for 1 h (n = 3). A computational model simulated TSL-Dox pharmacokinetics, including ECC filtration, and predicted cardiac Dox uptake. In animals receiving ECC, we were able to remove 576 ± 65 mg of Dox (29.7 ± 3.7% of the infused dose) within 1 h, with a 2.9-fold reduction of plasma AUC. Fluorescent monitoring enabled real-time quantification of blood concentration and removed drug. Computational modeling predicted that up to 59% of drug could be removed with an ideal filter, and that cardiac uptake can be reduced up to 7×. We demonstrated removal of drug remaining after tumor delivery, reduced plasma AUC, and reduced cardiac uptake, suggesting reduced toxicity.

Doxorubicin nanoformulations on therapy against cancer: An overview from the last 10 years

Doxorubicin (DOX) is a natural antibiotic with antineoplastic activity. It has been used for over 40 years and remains one of the most used drugs in chemotherapy for a variety of cancers. However, cardiotoxicity limits its use for long periods. To overcome this limitation, encapsulation in smart drug delivery systems (DDS) brings advantages in comparison with free drug administration (i.e., conventional anticancer drug therapy). In this review, we present the most relevant nanostructures used for DOX encapsulation over the last 10 years, such as liposomes, micelles and polymeric vesicles (i.e., polymersomes), micro/nanoemulsions, different types of polymeric nanoparticles and hydrogel nanoparticles, as well as novel approaches for DOX encapsulation. The studies highlighted here show these nanoformulations achieved higher solubility, improved tumor cytotoxicity, prolonged DOX release, as well as reduced side effects, among other interesting advantages.

Recombinant porphobilinogen deaminase targeted to the liver corrects enzymopenia in a mouse model of acute intermittent porphyria

[Figure: see text].

Smart NIR-II croconaine dye-peptide for enhanced photo-sonotheranostics of hepatocellular carcinoma

Background: Hepatocellular carcinoma (HCC) is associated with high morbidity and mortality rates. The development of novel nanomaterials represents an important direction for precise HCC theranostics. The combination of photothermal and sonodynamic therapy has provided great benefits for HCC therapy. Theranostic agents in the second near-infrared window (NIR-II, 1000-1700 nm) show great prospects because of their extraordinarily high detection sensitivity, resolution, and deep penetration. Methods: A sharp pH-sensitive self-assembling Glypican-3 (GPC3)-binding peptide (GBP) dye, CR-PEG-GBP, was developed as an intelligent nanoprobe for NIR-II imaging and photoacoustic (PA) imaging-guided photothermal therapy (PTT) and sonodynamic therapy (SDT) of HCC. Results: This small molecule assembled nanoprobe exhibited advantageous properties, such as responding to a decrease in pH (from normal tissue (pH 7.4) to the tumor microenvironment (pH ~6.5)) and aggregating - from small nanoprobes (<20 nm at pH 7.4) - into large nanoparticles (>160 nm at pH 6.5 and >510 nm at pH 5.5) that enables enhanced imaging and therapeutic effects. Because CR-PEG-GBP can self-aggregate in situ in an acidic tumor microenvironment, it shows high tumor accumulation and long tumor retention time, while being excretable from normal tissues and safe. Conclusions: This intelligent self-assembling small molecule strategy provides a simple yet efficient solution for HCC theranostics and may open up new avenues for designing clinically translatable probes for HCC treatment.

Bioinspired and Biomimetic Delivery Platforms for Cancer Vaccines

Cancer vaccines aim at eliciting tumor-specific responses for the immune system to identify and eradicate malignant tumor cells while sparing the normal tissues. Furthermore, cancer vaccines can potentially induce long-term immunological memory for antitumor responses, preventing metastasis and cancer recurrence, thus presenting an attractive treatment option in cancer immunotherapy. However, clinical efficacy of cancer vaccines has remained low due to longstanding challenges, such as poor immunogenicity, immunosuppressive tumor microenvironment, tumor heterogeneity, inappropriate immune tolerance, and systemic toxicity. Recently, bioinspired materials and biomimetic technologies have emerged to play a part in reshaping the field of cancer nanomedicine. By mimicking desirable chemical and biological properties in nature, bioinspired engineering of cancer vaccine delivery platforms can effectively transport therapeutic cargos to tumor sites, amplify antigen and adjuvant bioactivities, and enable spatiotemporal control and on-demand immunoactivation. As such, integration of biomimetic designs into delivery platforms for cancer vaccines can enhance efficacy while retaining good safety profiles, which contributes to expediting the clinical translation of cancer vaccines. Recent advances in bioinspired delivery platforms for cancer vaccines, existing obstacles faced, as well as insights and future directions for the field are discussed here.

Thermosensitive liposomes encapsulating hypericin: Characterization and photodynamic efficiency

The potent photodynamic properties of Hypericin (Hyp) elicit a range of light-dose-dependent anti-tumor activities. However, its low water solubility hampers its broad application. Therefore, the administration of Hyp into biological systems requires drug carriers that would enable sufficient bioavailability. Stimuli-triggered nanocarriers, which are sensitive to endogenous or exogenous stimuli, have become an attractive replacement for conventional therapeutic regimens. Herein, we produced optimized Hyp thermosensitive liposomes (Hyp-TSL), self-assembled from DPPC, DSPC, DSPE-PEG2000. Hyp-TSL displayed a hydrodynamic diameter below 100 nm with an adequate encapsulation efficiency of 94.5 % and good colloidal stability. Hyp-TSL exhibited thermal sensitivity over a narrow range with a phase transition temperature of 41.1 °C, in which liposomal destruction was evident in AFM images after elevated temperature above the phase transition temperature. The uptake of TSL-Hyp into MDA-MB-231 cells was significantly increased with hyperthermic treatment of 42 °C when compared to the uptake at a average physiological temperature of 37 °C. Consequent enhancement of cellular reactive oxygen species was observed after hyperthermic treatment at 42 °C. The half-maximal inhibitory concentration of Hyp TSL was reduced by 3.8 fold after hyperthermic treatment at 42 °C in comparison to treatment at 37 °C. Hyp-TSL were considered safe for intravenous applications as compared by hemocompatibility studies, where coagulation time was <50 s and hemolytic potential was <10%. Conclusively, the enhancement in tumor drug availability correlated with improved therapeutic outcomes.

Untargeted Large Volume Hyperthermia Reduces Tumor Drug Uptake From Thermosensitive Liposomes

Goal: The impact of hyperthermia (HT) method on tumor drug uptake with thermosensitive liposomes (TSL) is not well understood. Methods: We created realistic three-dimensional (3-D) computer models that simulate TSL-encapsulated doxorubicin (TSL-DOX) delivery in mouse tumors with three HT methods (thermistor probe (T), laser (L) and water bath (WB), at 15 min and 60 min HT duration), with corroborating in vivo studies. Results: Average computer model-predicted tumor drug concentrations (μg/g) were 8.8(T, 15 min), 21.0(T, 60 min), 14.1(L, 15 min), 25.2(L, 60 min), 9.4(WB, 15 min), and 8.7(WB, 60 min). Tumor fluorescence was increased by 2.6 × (T) and 1.6 × (L) when HT duration was extended from 15 to 60 min (p < 0.05), with no increase for WB HT. Pharmacokinetic analysis confirmed that water bath HT causes rapid depletion of encapsulated TSL-DOX in systemic circulation due to the large heated tissue volume. Conclusions: Untargeted large volume HT causes poor tumor drug uptake from TSL.

Computational modeling of thermal combination therapies by magneto-ultrasonic heating to enhance drug delivery to solid tumors

For the first time, inspired by magnetic resonance imaging-guidance high intensity focused ultrasound (MR-HIFU) technology, i.e., medication therapy and thermal ablation in one session, in a preclinical setting based on a developed mathematical model, the performance of doxorubicin (Dox) and its encapsulation have been investigated in this study. Five different treatment methods, that combine medication therapy with mild hyperthermia by MRI contrast (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma -{Fe}_{2}{O}_{3}$$\end{document}γ-Fe2O3) and thermal ablation via HIFU, are investigated in detail. A comparison between classical chemotherapy and thermochemistry shows that temperature can improve the therapeutic outcome by stimulating biological properties. On the other hand, the intravascular release of ThermoDox increases the concentration of free drug by 2.6 times compared to classical chemotherapy. The transport of drug in interstitium relies mainly on the diffusion mechanism to be able to penetrate deeper and reach the cancer cells in the inner regions of the tumor. Due to the low drug penetration into the tumor center, thermal ablation has been used for necrosis of the central areas before thermochemotherapy and ThermoDox therapy. Perfusion of the region around the necrotic zone is found to be damaged, while cells in the region are alive and not affected by medication therapy; so, there is a risk of tumor recurrence. Therefore, it is recommended that ablation be performed after the medication therapy. Our model describes a comprehensive assessment of MR-HIFU technology, taking into account many effective details, which can be a reliable guide towards the optimal use of drug delivery systems.

Nanomedicine Strategies to Enhance Tumor Drug Penetration in Pancreatic Cancer

Pancreatic cancer is one of the most malignant tumors with one of the worst survival rates due to its insidious onset and resistance to therapies. Most therapeutics show a desired anticancer effect in vitro; however, very poor efficacy in vivo because of the limited drug delivery and penetration into pancreatic tumors attributed to the abundance of the tumor stroma, ie, the fibrotic tumor microenvironment surrounding the cancer cells. For a better understanding of the challenges posed by the pancreatic tumor stroma, we outline the key features of the tumor microenvironment. Then we highlight major strategies used to tackle the challenges to improve drug penetration into the tumor and achieve enhanced efficacy (pre)clinically. Furthermore, we describe nanomedicine strategies to modulate the tumor stroma, degrade the extracellular matrix, and co-deliver multi-functional drugs, to improve the chemotherapeutics delivery and penetration into pancreatic tumors.

Effects of Surface Charge, PEGylation and Functionalization with Dipalmitoylphosphatidyldiglycerol on Liposome-Cell Interactions and Local Drug Delivery to Solid Tumors via Thermosensitive Liposomes

Purpose

Previous studies demonstrated the possibility of targeting tumor-angiogenic endothelial cells with positively charged nanocarriers, such as cationic liposomes. We investigated the active targeting potential of positively charged nanoparticles in combination with the heat-induced drug release function of thermosensitive liposomes (TSL). This novel dual-targeted approach via cationic TSL (CTSL) was thoroughly explored using either a novel synthetic phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphodiglycerol (DPPG₂) or a conventional polyethylene glycol (PEG) surface modification. Anionic particles containing either DPPG₂ or PEG were also included in the study to highlight difference in tumor enrichment driven by surface charge. With this study, we aim to provide a deep insight into the main differences between DPPG₂- and PEG-functionalized liposomes, focusing on the delivery of a well-known cytotoxic drug (doxorubicin; DOX) in combination with local hyperthermia (HT, 41–43°C).

Materials and Methods

DPPG₂- and PEG-based cationic TSLs (PG₂-CTSL/PEG-CTSL) were thoroughly analyzed for size, surface charge, and heat-triggered DOX release. Cancer cell targeting and DOX delivery was evaluated by FACS, fluorescence imaging, and HPLC. In vivo particle behavior was analyzed by assessing DOX biodistribution with local HT application in tumor-bearing animals.

Results

The absence of PEG in PG₂-CTSL promoted more efficient liposome–cell interactions, resulting in a higher DOX delivery and cancer cell toxicity compared with PEG-CTSL. By exploiting the dual-targeting function of CTSLs, we were able to selectively trigger DOX release in the intracellular compartment by HT. When tested in vivo, local HT promoted an increase in intratumoral DOX levels for all (C)TSLs tested, with DOX enrichment factors ranging from 3 to 14-fold depending on the type of formulation.

Conclusion

Cationic particles showed lower hemocompatibility than their anionic counterparts, which was partially mitigated when PEG was grafted on the liposome surface. DPPG₂-based anionic TSL showed optimal local drug delivery compared to all other formulations tested, demonstrating the potential advantages of using DPPG₂ lipid in designing liposomes for tumor-targeted applications.

Pressure-driven spreadable deferoxamine-laden hydrogels for vascularized skin flaps

The development of hydrogels that support vascularization to improve the survival of skin flaps, yet establishing homogeneous angiogenic niches without compromising the ease of use in surgical settings remains a challenge. Here, pressure-driven spreadable hydrogels were developed utilizing beta-sheet rich silk nanofiber materials. These silk nanofiber-based hydrogels exhibited excellent spreading under mild pressure to form a thin coating to cover all the regions of the skin flaps. Deferoxamine (DFO) was loaded onto the silk nanofibers to support vascularization and these DFO-laden hydrogels were implanted under skin flaps in rats to fill the interface between the wound bed and the flap using the applied pressure. The thickness of the spread hydrogels was below 200 μm, minimizing the physical barrier effects from the hydrogels. The distribution of the hydrogels provided homogeneous angiogenic stimulation, accelerating rapid blood vessel network formation and significantly improving the survival of the skin flaps. The hydrogels also modulated the immune reactions, further facilitating the regeneration of the skin flaps. Considering the homogeneous distribution at the wound sites, improved vascularization, reduced barrier effects and low inflammation, these hydrogels appear to be promising candidates for use in tissue repair where a high blood supply is in demand. The pressure-driven spreading properties should simplify the use of the hydrogels in surgical settings to facilitate clinical translation.

Development, evaluation and biodistribution of stealth liposomes of 5-fluorouracil for effective treatment of breast cancer

The current research was undertaken to design stealth liposomes of 5-Fluorouracil for reducing its cardiotoxicity and prolong the half-life by developing long-circulating liposomes. The liposomes were prepared by the NH₄EDTA gradient method, where EDTA is used as a cardioprotectant. Ascorbyl-6-palmitate was also used which helped for the synergistic effect of 5-Fluorouracil to counteract the cancer cells and provide promising application in the treatment of breast cancer cells. Taguchi design was used for screening of formulation and HSPC phospholipid was selected. The drug-excipient compatibility was checked through FTIR which showed all the excipients were compatible with the drug. The formulation was optimized by using 3² factorial design. The drug to lipid ratio (1:5) and Ascorbyl-6-Palmitate concentration (15 mg) were selected. The vesicle size of the prepared liposomes was found to be 70.12 ± 0.58 nm and uniform distribution was observed. The zeta potential and entrapment efficiency of the stealth liposomes were found -16.28 mV and 92 ± 0.007% respectively. In-vitro drug release study of formulation showed drug release of 63.50 ± 0.94% in 24 hrs. The formulation was sterilized by 0.22 µm Mixed cellulose esters (MCE) membrane filter and passed sterility test. Moreover, a biodistribution study was performed by Fluorescence microscopy and by HPLC method, which showed formulation was circulated for 24 hours. Finally, a cell line study indicated that prepared formulation possess greater anti-tumour activity. The cardiotoxicity study revealed that the stealth liposomes have minimum cardiotoxicity as compare to the plain drug.

Externally triggered smart drug delivery system encapsulating idarubicin shows superior kinetics and enhances tumoral drug uptake and response

Rationale: Increasing the bioavailable drug level in a tumor is the key to enhance efficacy of chemotherapy. Thermosensitive smart drug delivery systems (SDDS) in combination with local hyperthermia facilitate high local drug levels, thus improving uptake in the tumor. However, inability to rapidly and efficiently absorb the locally released drug results in reduced efficacy, as well as undesired redistribution of the drug away from the tumor to the system.

Methods: Based on this paradigm we propose a novel approach in which we replaced doxorubicin (DXR), one of the classic drugs for nanocarrier-based delivery, with idarubicin (IDA), a hydrophobic anthracycline used solely in the free form for treatment hematologic cancers. We established a series of in vitro and in vivo experiments to in depth study the kinetics of SDDS-based delivery, drug release, intratumor biodistribution and subsequent cell uptake.

Results: We demonstrate that IDA is taken up over 10 times more rapidly by cancer cells than DXR in vitro. Similar trend is observed in in vivo online imaging and less drug redistribution is shown for IDA, together resulting in 4-times higher whole tumor drug uptake for IDA vs. DXR. Together his yielded an improved intratumoral drug distribution for IDA-SDDS, translating into superior tumor response compared to DXR-SDDS treatment at the same dose. Thus, IDA - a drug that is not used for treatment of solid cancers - shows superior therapeutic index and better outcome when administered in externally triggered SDDS.

Conclusions: We show that a shift in selection of chemotherapeutics is urgently needed, away from the classic drugs towards selection based on properties of a chemotherapeutic in context of the nanoparticle and delivery mode, to maximize the therapeutic efficacy.

Modulating the Heat Stress Response to Improve Hyperthermia-Based Anticancer Treatments

Simple Summary

Hyperthermia is a method to expose a tumor to elevated temperatures. Heating of the tumor promotes the effects of various treatment regimens that are based on chemo and radiotherapy. Several aspects, however, limit the efficacy of hyperthermia-based treatments. This review provides an overview of the effects and limitations of hyperthermia and discusses how current drawbacks of the therapy can potentially be counteracted by inhibiting the heat stress response—a mechanism that cells activate to defend themselves against hyperthermia.

Abstract

Cancer treatments based on mild hyperthermia (39–43 °C, HT) are applied to a widening range of cancer types, but several factors limit their efficacy and slow down more widespread adoption. These factors include difficulties in adequate heat delivery, a short therapeutic window and the acquisition of thermotolerance by cancer cells. Here, we explore the biological effects of HT, the cellular responses to these effects and their clinically-relevant consequences. We then identify the heat stress response—the cellular defense mechanism that detects and counteracts the effects of heat—as one of the major forces limiting the efficacy of HT-based therapies and propose targeting this mechanism as a potentially universal strategy for improving their efficacy.

Diseases and conditions that impact maternal and fetal health and the potential for nanomedicine therapies

Maternal mortality rates in the United States have steadily increased since 1987 to the current rate of over 16 deaths per 100,000 live births. Whereas most of these deaths are related to an underlying condition, such as cardiovascular disease, many pregnant women die from diseases that emerge as a consequence of pregnancy. Both pre-existing and emergent diseases and conditions are difficult to treat in pregnant women because of the potential harmful effects of the treatment on the developing fetus. Often the health of the woman and the health of the baby are at odds and must be weighed against each other when medical treatment is needed, frequently leading to iatrogenic preterm birth. However, the use of engineered nanomedicines has the potential to fill the treatment gap for pregnant women. This review describes several conditions that may afflict pregnant women and fetuses and introduces how engineered nanomedicines may be used to treat these illnesses. Although the field of maternal-fetal nanomedicine is in its infancy, with additional research and development, engineered nanotherapeutics may greatly improve outcomes for pregnant women and their offspring in the future.

Phase I feasibility study of Magnetic Resonance guided High Intensity Focused Ultrasound-induced hyperthermia, Lyso-Thermosensitive Liposomal Doxorubicin and cyclophosphamide in de novo stage IV breast cancer patients: study protocol of the i-GO study

INTRODUCTION

In breast cancer, local tumour control is thought to be optimised by administering higher local levels of cytotoxic chemotherapy, in particular doxorubicin. However, systemic administration of higher dosages of doxorubicin is hampered by its toxic side effects. In this study, we aim to increase doxorubicin deposition in the primary breast tumour without changing systemic doxorubicin concentration and thus without interfering with systemic efficacy and toxicity. This is to be achieved by combining Lyso-Thermosensitive Liposomal Doxorubicin (LTLD, ThermoDox, Celsion Corporation, Lawrenceville, NJ, USA) with mild local hyperthermia, induced by Magnetic Resonance guided High Intensity Focused Ultrasound (MR-HIFU). When heated above 39.5°C, LTLD releases a high concentration of doxorubicin intravascularly within seconds. In the absence of hyperthermia, LTLD leads to a similar biodistribution and antitumour efficacy compared with conventional doxorubicin.

METHODS AND ANALYSIS

This is a single-arm phase I study in 12 chemotherapy-naïve patients with de novo stage IV HER2-negative breast cancer. Previous endocrine treatment is allowed. Study treatment consists of up to six cycles of LTLD at 21-day intervals, administered during MR-HIFU-induced hyperthermia to the primary tumour. We will aim for 60 min of hyperthermia at 40°C-42°C using a dedicated MR-HIFU breast system (Profound Medical, Mississauga, Canada). Afterwards, intravenous cyclophosphamide will be administered. Primary endpoints are safety, tolerability and feasibility. The secondary endpoint is efficacy, assessed by radiological response.This approach could lead to optimal loco-regional control with less extensive or even no surgery, in de novo stage IV patients and in stage II/III patients allocated to receive neoadjuvant chemotherapy.

ETHICS AND DISSEMINATION

This study has obtained ethical approval by the Medical Research Ethics Committee Utrecht (Protocol NL67422.041.18, METC number 18-702). Informed consent will be obtained from all patients before study participation. Results will be published in an academic peer-reviewed journal.

TRIAL REGISTRATION NUMBERS

NCT03749850, EudraCT 2015-005582-23.

Polar Lipid Fraction E from Sulfolobus acidocaldarius and Dipalmitoylphosphatidylcholine Can Form Stable yet Thermo-Sensitive Tetraether/Diester Hybrid Archaeosomes with Controlled Release Capability

Archaeosomes have drawn increasing attention in recent years as novel nano-carriers for therapeutics. The main obstacle of using archaeosomes for therapeutics delivery has been the lack of an efficient method to trigger the release of entrapped content from the otherwise extremely stable structure. Our present study tackles this long-standing problem. We made hybrid archaeosomes composed of tetraether lipids, called the polar lipid fraction E (PLFE) isolated from the thermoacidophilic archaeon Sulfolobus acidocaldarius, and the synthetic diester lipid dipalmitoylphosphatidylcholine (DPPC). Differential polarized phase-modulation and steady-state fluorometry, confocal fluorescence microscopy, zeta potential (ZP) measurements, and biochemical assays were employed to characterize the physical properties and drug behaviors in PLFE/DPPC hybrid archaeosomes in the presence and absence of live cells. We found that PLFE lipids have an ordering effect on fluid DPPC liposomal membranes, which can slow down the release of entrapped drugs, while PLFE provides high negative charges on the outer surface of liposomes, which can increase vesicle stability against coalescence among liposomes or with cells. Furthermore, we found that the zeta potential in hybrid archaeosomes with 30 mol% PLFE and 70 mol% DPPC (designated as PLFE/DPPC(3:7) archaeosomes) undergoes an abrupt increase from −48 mV at 37 °C to −16 mV at 44 °C (termed the ZP transition), which we hypothesize results from DPPC domain melting and PLFE lipid ‘flip-flop’. The anticancer drug doxorubicin (DXO) can be readily incorporated into PLFE/DPPC(3:7) archaeosomes. The rate constant of DXO release from PLFE/DPPC(3:7) archaeosomes into Tris buffer exhibited a sharp increase (~2.5 times), when the temperature was raised from 37 to 42 °C, which is believed to result from the liposomal structural changes associated with the ZP transition. This thermo-induced sharp increase in drug release was not affected by serum proteins as a similar temperature dependence of drug release kinetics was observed in human blood serum. A 15-min pre-incubation of PLFE/DPPC(3:7) archaeosomal DXO with MCF-7 breast cancer cells at 42 °C caused a significant increase in the amount of DXO entering into the nuclei and a considerable increase in the cell’s cytotoxicity under the 37 °C growth temperature. Taken together, our data suggests that PLFE/DPPC(3:7) archaeosomes are stable yet potentially useful thermo-sensitive liposomes wherein the temperature range (from 37 to 42–44 °C) clinically used for mild hyperthermia treatment of tumors can be used to trigger drug release for medical interventions.

Hyperthermia and Temperature-Sensitive Nanomaterials for Spatiotemporal Drug Delivery to Solid Tumors

Nanotechnology has great capability in formulation, reduction of side effects, and enhancing pharmacokinetics of chemotherapeutics by designing stable or long circulating nano-carriers. However, effective drug delivery at the cellular level by means of such carriers is still unsatisfactory. One promising approach is using spatiotemporal drug release by means of nanoparticles with the capacity for content release triggered by internal or external stimuli. Among different stimuli, interests for application of external heat, hyperthermia, is growing. Advanced technology, ease of application and most importantly high level of control over applied heat, and as a result triggered release, and the adjuvant effect of hyperthermia in enhancing therapeutic response of chemotherapeutics, i.e., thermochemotherapy, make hyperthermia a great stimulus for triggered drug release. Therefore, a variety of temperature sensitive nano-carriers, lipid or/and polymeric based, have been fabricated and studied. Importantly, in order to achieve an efficient therapeutic outcome, and taking the advantages of thermochemotherapy into consideration, release characteristics from nano-carriers should fit with applicable clinical thermal setting. Here we introduce and discuss the application of the three most studied temperature sensitive nanoparticles with emphasis on release behavior and its importance regarding applicability and therapeutic potentials.

Inverse Electron Demand Diels-Alder Reactions in the Liposomal Membrane Accelerates Release of the Encapsulated Drugs

Bio-orthogonal inverse electron demand Diels-Alder (IEDDA) reactions between liposomes containing a tetrazine-based (Tz) compound and 2-norbornene (2-NB) could be a novel trigger for accelerating drug release from the liposomes via temporary membrane destabilization, as shown in our previous report. Herein, we evaluated the in vitro drug release using NB derivatives with carboxyl groups [5-norbornene-2-carboxylic acid (NBCOOH) and 5-norbornene-2,3-dicarboxylic acid (NB(COOH)₂)] to investigate the effects of substituents at the NB backbone on the drug release rate. First, POTz-liposome composed of a Tz compound (2-hexadecyl-N-(6-(6-(pyridin-2-yl)-1,2,4,5-tetrazin-3-yl)pyridin-3-yl)octadecanamide) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) were prepared. The mass spectrometry analysis revealed the binding of NB derivatives to the Tz compound via the IEDDA reaction after the POTz-liposome reacted with the NB derivatives. Indium-111-labeled diethylenetriaminepentaacetic acid (¹¹¹In-DTPA) was encapsulated inside the liposomes, and the drug release rate was quantified by measuring radioactivity. At 24 h after incubation with 2-NB, NBCOOH, and NB(COOH)₂, the release rates of ¹¹¹In-DTPA from POTz-liposome were 21.0, 80.8, and 23.3%, respectively, which were significantly higher than those of POTz-liposome that was not treated with NB derivatives (4.2%), indicating the involvement of the IEDDA reaction for prompting drug release. Additionally, a thermodynamic evaluation using Langmuir monolayers was conducted to explore the mechanism of the accelerated drug release. An increase in membrane fluidity and a reduction in intermolecular repulsion between POPC and the Tz compound were observed after the reaction with NB derivatives, especially for NBCOOH. Thus, the IEDDA reaction in the liposomal membrane could be a potent trigger for accelerating the release of encapsulated drugs by regulating membrane fluidity and intermolecular repulsion in the liposomal membrane.

Self-assembly of four generations of RNA dendrimers for drug shielding with controllable layer-by-layer release

Chemical dendrimers have been shown to be a promising drug delivery platform due to their advantageous properties such as monodispersity, multivalency and branched structure. Taking advantage of self-assembly and its intrinsic negative charge, we used RNA as the building block for dendrimer construction to eliminate complex synthesis procedures and cationic charge-related toxicity. Oligo ribonucleotides produced by solid phase chemical synthesis allow the large-scale manufacture of homologous RNA dendrimers. Employing concepts from RNA nanotechnology enabled the controllable production of dendrimers with generations from G1, G2, G3, to G4 with layer-by-layer release capability. The conjugation of functional groups into individual RNA strands and the incorporation of functionalized RNA strands into the dendrimers at different sites have been reported. Anticancer drugs loaded into RNA dendrimers showed comparable cancer cell inhibition effect to free drugs. Encapsulation of cell binding ligands and hydrophobic drugs within the dendrimer significantly reduced the efficiency of cell binding and protein binding respectively, demonstrating the shielding effect of RNA dendrimers. The results imply a potential application of RNA dendrimer for delivery, shielding and controlled release of hydrophobic drugs in vivo.

Enzyme-Responsive Nanoparticles for Anti-tumor Drug Delivery

The past few decades have seen great progress in the exploration of nanoparticles (NPs) as novel tools for cancer treatments and diagnosis. Practical and reliable application of nanoparticle-based technology in clinical transformation remains nevertheless an ongoing challenge. The design, preparation, and evaluation of various smart NPs with specific physicochemical responses in tumor-related physiological conditions have been of great interests in both academic and clinical research. Of particular, smart enzyme-responsive nanoparticles can predictively and selectively react with specific enzymes expressed in tumor tissues, leading to targeted delivery of anti-tumor drugs, reduced systemic toxicity, and improved therapeutic effect. In addition, NPs interact with internal enzymes usually under mild conditions (low temperature, aqueous media, neutral or close to neutral pH) with high efficiency. In this review, recent advances in the past 5 years in enzyme-responsive nanoparticles for anti-tumor drug delivery are summarized and discussed. The following contents are divided based on the different action sites of enzymes toward NPs, notably hydrophobic core, cleavable/uncleavable linker, hydrophilic crown, and targeting ligand. Enzyme-engaged destruction of any component of these delicate nanoparticle structures could result in either targeting drug delivery or controlled drug release.

Magnetic resonance activatable thermosensitive liposomes for controlled doxorubicin delivery

To limit the massive cytotoxicity of chemotherapeutic agents, it is desirable to establish an appropriate subtle blend of formulation design based on a dual-responsive strategy. In this study, a combined therapeutic platform based on magnetic thermosensitive liposomes (Lip_TS-GD) was developed. The incorporation of chelated-gadolinium imparted magnetic properties to thermosensitive liposomes (Lip_TS). The application of an ultra high field magnetic resonance imaging (UHF-MRI) induced hyperthermia, thus provided an improved chemotherapeutic effect of Doxorubicin (DOX). The paramagnetic platform demonstrated thermal sensitivity over a narrow temperature range starting at 37.8 °C, hence the release of DOX from Lip_TS-GD can be well triggered by inducing hyperthermia using UHF-MRI application. The prepared Lip_TS-GD were below 200 nm in diameter and an adequate release of DOX reaching 68% was obtained after 1 h UHF-MRI exposure. Profoundly, triple-negative breast cancer (TNBC) cells that were treated with Lip_TS-GD and subjected thereafter to UHF-MRI exposure for 60 min showed 36% viability. Hemocompatibility studies of Lip_TS-GD showed a physiological coagulation time and minimal hemolytic potential. Conclusively, Lip_TS-GD guided local delivery of DOX to solid tumors will potentially raise the therapeutic index, thus reducing the required dose and frequency of DOX administered systemically without influencing the adjacent tissues.

In Vivo Assessment of Thermosensitive Liposomes for the Treatment of Port Wine Stains by Antifibrinolytic Site-Specific Pharmaco-Laser Therapy

Antifibrinolytic site-specific pharmaco-laser therapy (SSPLT) is an experimental treatment modality for refractory port wine stains (PWS). Conceptually, antifibrinolytic drugs encapsulated in thermosensitive liposomes are delivered to thrombi that form in semi-photocoagulated PWS blood vessels after conventional laser treatment. Local release of antifibrinolytics is induced by mild hyperthermia, resulting in hyperthrombosis and complete occlusion of the target blood vessel (clinical endpoint). In this study, 20 thermosensitive liposomal formulations containing tranexamic acid (TA) were assayed for physicochemical properties, TA:lipid ratio, encapsulation efficiency, and endovesicular TA concentration. Two candidate formulations (DPPC:DSPE-PEG, DPPC:MPPC:DSPE-PEG) were selected based on optimal properties and analyzed for heat-induced TA release at body temperature (T), phase transition temperature (T_m), and at T > T_m. The effect of plasma on liposomal stability at 37 °C was determined, and the association of liposomes with platelets was examined by flow cytometry. The accumulation of PEGylated phosphocholine liposomes in laser-induced thrombi was investigated in a hamster dorsal skinfold model and intravital fluorescence microscopy. Both formulations did not release TA at 37 °C. Near-complete TA release was achieved at T_m within 2.0–2.5 min of heating, which was accelerated at T > T_m. Plasma exerted a stabilizing effect on both formulations. Liposomes showed mild association with platelets. Despite positive in vitro results, fluorescently labeled liposomes did not sufficiently accumulate in laser-induced thrombi in hamsters to warrant their use in antifibrinolytic SSPLT, which can be solved by coupling thrombus-targeting ligands to the liposomes.

A novel kinetic model to describe the ultra-fast triggered release of thermosensitive liposomal drug delivery systems

Thermosensitive liposomes, as one of the stimuli-responsive drug delivery systems, receive growing attention, due to their ability to generate rapid and massive drug release in the heated area, and marginal release of contents in non-heated parts of the body. This typical triggered release behavior cannot be fitted adequately by most of the current mathematical kinetic models. The aim of this study was to establish the proper kinetic equation to describe the rapid release of drugs from trigger-sensitive drug delivery systems. We summarized all commonly used kinetic models mentioned in the literature and fitted the release data with these models, finding that only the Korsmeyer-Peppas and the Weibull models show acceptable fitting results. To better describe the release from thermosensitive liposomes with a size below 100 nm, we took Laplace pressure as a release-driving force and proposed a new equation that demonstrates improved fitting in liposomes ranging down to a size of 70 nm. Our new kinetic model shows desirable fitting, not only at the optimal temperature but also of releases within the whole release-temperature range, providing a useful kinetic model to describe release profiles of smaller nano-sized stimuli-responsive drug delivery systems.

Potential drug delivery nanosystems for improving tumor penetration

Nanosystems, as one of the most important drug delivery systems, play a crucial rule in tumor therapy. However, the deep tumor penetration is retarded by the tumor physiological factors and nanomedicine properties. In this review, we firstly elaborate the factors which impact tumor penetration, including the tumor physiological factors and nanomedicine properties. Then, the latest and potential drug delivery nanosystems for improving tumor penetration are summarized and analyzed in detail. Moreover, recent combination therapies for improving penetration are described to enhance penetration. Finally, we summarize the typical clinical therapies of potential drug delivery nanosystems.

A moderate thermal dose is sufficient for effective free and TSL based thermochemotherapy

Hyperthermia, i.e. heating the tumor to a temperature of 40-43 °C is considered by many a valuable treatment to sensitize tumor cells to radiotherapy and chemotherapy. In recent randomized trials the great potential of adding hyperthermia to chemotherapy was demonstrated for treatment of high risk soft tissue sarcoma: +11.4% 5 yrs. overall survival (OS) and for ovarian cancer with peritoneal involvement nearly +12 months OS gain. As a result interest in combining chemotherapy with hyperthermia, i.e. thermochemotherapy, is growing. Extensive biological research has revealed that hyperthermia causes multiple effects, from direct cell kill to improved oxygenation, whereby each effect has a specific temperature range. Thermal sensitization of the tumor cell for chemotherapy occurs for many drugs at temperatures ranging from 40 to 42 °C with little additional increase of sensitization at higher temperatures. Increasing perfusion/oxygenation and increased extravasation are two other important hyperthermia induced mechanisms. The combination of free drug and hyperthermia has not been found to increase tumor drug concentration. Hence, enhanced effectiveness of free drug will depend on the thermal sensitization of the tumor cells for the applied drug. In contrast to free drugs, experimental animal studies combining hyperthermia and thermo-sensitive liposomal (TSL) drugs delivery have demonstrated to result in a substantial increase of the drug concentration in the tumor. For TSL based chemotherapy, hyperthermia is critical to both increase perfusion and extravasation as well as to trigger TSL drug release, whereby the temperature controlled induction of a local high drug concentration in a highly permeable vessel is driving the enhanced drug uptake in the tumor. Increased drug concentrations up to 26 times have been reported in rodents. Good control of the tissue temperature is required to keep temperatures below 43 °C to prevent vascular stasis. Further, careful timing of the drug application relative to the start of heating is required to benefit optimal from the combined treatment. From the available experimental data it follows that irrespective whether chemotherapy is applied as free drug or using a thermal sensitive liposomal carrier, the optimal thermal dose for thermochemotherapy should be 40-42 °C for 30-60 min, i.e. equivalent to a CEM43 of 1-15 min. Timing is critical: most free drug should be applied simultaneous with heating, whereas TSL drugs should be applied 20-30 min after the start of hyperthermia.

Hyperthermia and smart drug delivery systems for solid tumor therapy

Chemotherapy is a cornerstone of cancer therapy. Irrespective of the administered drug, it is crucial that adequate drug amounts reach all cancer cells. To achieve this, drugs first need to be absorbed, then enter the blood circulation, diffuse into the tumor interstitial space and finally reach the tumor cells. Next to chemoresistance, one of the most important factors for effective chemotherapy is adequate tumor drug uptake and penetration. Unfortunately, most chemotherapeutic agents do not have favorable properties. These compounds are cleared rapidly, distribute throughout all tissues in the body, with only low tumor drug uptake that is heterogeneously distributed within the tumor. Moreover, the typical microenvironment of solid cancers provides additional hurdles for drug delivery, such as heterogeneous vascular density and perfusion, high interstitial fluid pressure, and abundant stroma. The hope was that nanotechnology will solve most, if not all, of these drug delivery barriers. However, in spite of advances and decades of nanoparticle development, results are unsatisfactory. One promising recent development are nanoparticles which can be steered, and release content triggered by internal or external signals. Here we discuss these so-called smart drug delivery systems in cancer therapy with emphasis on mild hyperthermia as a trigger signal for drug delivery.

Real-time fluorescence imaging for visualization and drug uptake prediction during drug delivery by thermosensitive liposomes

Objective: Thermosensitive liposomal doxorubicin (TSL-Dox) is a promising stimuli-responsive nanoparticle drug delivery system that rapidly releases the contained drug in response to hyperthermia (HT) (>40 °C). Combined with localized heating, TSL-Dox allows highly localized delivery. The goals of this study were to demonstrate that real-time fluorescence imaging can visualize drug uptake during delivery, and can predict tumor drug uptake. Methods: Nude mice carrying subcutaneous tumors (Lewis lung carcinoma) were anesthetized and injected with TSL-Dox (5 mg/kg dose). Localized HT was induced by heating tumors for 15, 30 or 60 min via a custom-designed HT probe placed superficially at the tumor location. In vivo fluorescence imaging (excitation 523 nm, emission 610 nm) was performed before, during, and for 5 min following HT. After imaging, tumors were extracted, drug uptake was quantified by high-performance liquid chromatography, and correlated with in vivo fluorescence. Plasma samples were obtained before and after HT to measure TSL-Dox pharmacokinetics. Results: Local drug uptake could be visualized in real-time during HT. Compared to unheated control tumors, fluorescence of heated tumors increased by 4.6-fold (15 min HT), 9.3-fold (30 min HT), and 13.2-fold (60 min HT). HT duration predicted tumor drug uptake (p = .02), with tumor drug concentrations of 4.2 ± 1.3 µg/g (no HT), 7.1 ± 5.9 µg/g (15 min HT), 14.1 ± 6.7 µg/g (30 min HT) and 21.4 ± 12.6 µg/g (60 min HT). There was good correlation (R² = 0.67) between fluorescence of the tumor region and tumor drug uptake. Conclusions: Real-time in vivo fluorescence imaging can visualize drug uptake during delivery, and can predict tumor drug uptake.

Development and characteristics of novel sonosensitive liposomes for vincristine bitartrate

The aim of drug delivery is to increase therapeutic efficacy. Externally triggered drug delivery systems enable site-specific and time-controlled drug release. To achieve this goal, our strategy was based on ultrasound-triggered release of an anticancer agent from sonosensitive liposomes (SL). To realize the ultrasound-triggered drug release, a lipophilic sonosensitizer, hematoporphyrin monomethyl ether (HMME) was incorporated into the lipid bilayer of liposomes. Once irradiated by the ultrasound in tumor tissues, the sonodynamic effect generated by HMME could lead to an efficient disruption of the lipid bilayer in the SL. After encapsulating vincristine bitartrate (VIN) as the model drug, the ultrasound-triggered lipid bilayer breakdown can trigger the instant release of VIN, enabling ultrasound-controlled chemotherapy with great specificity. In the in vitro and in vivo studies, by integrating tumor-specific targeting and stimuli-responsive controlled release into one system, VIN-loaded SL showed excellent antitumor efficacy. The SL could potentially produce viable clinical strategies for improved targeting efficiency of VIN for the treatment of related cancer. More importantly, this report provides an example of controlled release by means of a novel class of ultrasound triggering system.

Extravasating Neutrophils Open Vascular Barrier and Improve Liposomes Delivery to Tumors

Liposomes are the most extensively used nanocarriers in cancer therapy. Despite the advantages these vehicles provide over free drugs, there are still limitations with regards to the efficiency of liposomes delivery to tumors and off-target accumulation. A better understanding of nanodrugs extravasation mechanisms in different tumor types and normal vessels is needed to improve their antitumor activity. We used intravital microscopy to track for fluorescent liposomes behavior in xenograft tumor models (murine breast cancer 4T1 and melanoma B16, human prostate cancer 22Rv1) and normal skin and identified two distinct extravasation patterns. Microleakage, a local perivascular nanoparticle deposition, was found both in malignant and healthy tissues. This type of liposomes leakage does not provide access to tumor cells and is presumably responsible for drug deposition in normal tissues. In contrast, macroleakage penetrated deep into tissues and localized predominantly on the tumor-host interface. Although neutrophils did not uptake liposomes, their extravasation appeared to initiate both micro- and macroleakages. Based on neutrophils and liposomes extravasation dynamics, we hypothesized that microleakage and macroleakage are subsequent steps of the extravasation process corresponding to liposomes transport through endothelial and subendothelial barriers. Of note, extravasation spots were detected more often in the proximity of neutrophils, and across studied tumor types, neutrophils counts correlated with leakage frequencies. Reduced liposomes accumulation in 4T1 tumors upon Ly6G depletion further corroborated neutrophils role in nanoparticles delivery. Elucidating liposomes extravasation routes has a potential to help improve existing strategies and develop effective nanodrugs for 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.