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

Polymeric Phthalocyanine-Based Nanosensitizers for Enhanced Photodynamic and Sonodynamic Therapies

Photodynamic therapy and sonodynamic therapy are two highly promising modalities for cancer treatment. The latter holds an additional advantage in deep-tumor therapy owing to the deep penetration of the ultrasonic radiation. The therapeutic efficacy depends highly on the photo/ultrasound-responsive properties of the sensitizers as well as their tumor-localization property and pharmacokinetics. A novel nanosensitizer system based on a polymeric phthalocyanine (pPC-TK) is reported herein in which the phthalocyanine units are connected with cleavable thioketal linkers. Such polymer could self-assemble in water forming nanoparticles with a hydrodynamic diameter of 48 nm. The degradable and flexible thioketal linkers could effectively inhibit the π-π stacking of the phthalocyanine units, rendering the resulting nanoparticles an efficient generator of reactive oxygen species upon light or ultrasonic irradiation. The nanosensitizer could be internalized into cancer cells readily, inducing cell death by efficient photodynamic and sonodynamic effects. The potency is significantly higher than that of the monomeric phthalocyanine (PC-4COOH). The nanosensitizer could also effectively inhibit the growth of tumor in liver tumor-bearing mice by these two therapies without causing noticeable side effects. More importantly, it could also retard the growth of a deep-located orthotopic liver tumor in vivo by sonodynamic therapy.

Pharmacokinetic behaviors of soft nanoparticulate formulations of chemotherapeutics

Chemotherapeutic treatment with conventional drug formulations pose numerous challenges, such as poor solubility, high cytotoxicity and serious off-target side effects, low bioavailability, and ultimately subtherapeutic tumoral concentration leading to poor therapeutic outcomes. In the field of Nanomedicine, advances in nanotechnology have been applied with great success to design and develop novel nanoparticle-based formulations for the treatment of various types of cancer. The approval of the first nanomedicine, Doxil® (liposomal doxorubicin) in 1995, paved the path for further development for various types of novel delivery platforms. Several different types of nanoparticles, especially organic (soft) nanoparticles (liposomes, polymeric micelles, and albumin-bound nanoparticles), have been developed and approved for several anticancer drugs. Nanoparticulate drug delivery platform have facilitated to overcome of these challenges and offered key advantages of improved bioavailability, higher intra-tumoral concentration of the drug, reduced toxicity, and improved efficacy. This review introduces various commonly used nanoparticulate systems in biomedical research and their pharmacokinetic (PK) attributes, then focuses on the various physicochemical and physiological factors affecting the in vivo disposition of chemotherapeutic agents encapsulated in nanoparticles in recent years. Further, it provides a review of the current landscape of soft nanoparticulate formulations for the two most widely investigated anticancer drugs, paclitaxel, and doxorubicin, that are either approved or under investigation. Formulation details, PK profiles, and therapeutic outcomes of these novel strategies have been discussed individually and in comparison, to traditional formulations. This article is categorized under: Nanotechnology Approaches to Biology > Cells at the Nanoscale Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Chemophototherapeutic Ablation of Doxorubicin-Resistant Human Ovarian Tumor Cells

Porphyrin-phospholipid (PoP) liposomes loaded with Doxorubicin (Dox) have been demonstrated to be an efficient vehicle for chemophototherapy (CPT). Multidrug resistance (MDR) of cancer cells is a problematic phenomenon in which tumor cells develop resistance to chemotherapy. Herein, we report that Dox-resistant tumor cells can be ablated using our previously described formulation termed long-circulating Dox loaded in PoP liposomes (LC-Dox-PoP), which is a PEGylated formulation containing 2 mol. % of the PoP photosensitizer. In vitro studies using free Dox and LC-Dox-PoP showed that human ovarian carcinoma A2780 cells were more susceptible to Dox compared to the corresponding Dox-resistant A2780-R cells. When CPT was applied with LC-Dox-PoP liposomes, effective killing of both nonresistant and resistant A2780 cell lines was observed. An in vivo study to assess the efficiency of LC-Dox-PoP showed effective tumor shrinkage and prolonged survival of athymic nude mice bearing subcutaneous Dox-resistant A2780-R tumor xenografts when they were irradiated with a red laser. Biodistribution analysis demonstrated enhanced tumoral drug uptake in Dox-resistant tumors with CPT, suggesting that increased drug delivery was sufficient to induce ablation of resistant tumor cells.

Immune checkpoint blockade enhances chemophototherapy in a syngeneic pancreatic tumor model

Pancreatic cancer (PaCa) suffers from poor treatment options for locally advanced cases. Chemophototherapy (CPT) is an emerging anti-tumor modality, and porphyrin–phospholipid liposomes have been shown to be versatile drug carriers for CPT in preclinical rodent models. Here we show that in the syngeneic subcutaneous KPC PaCa tumor model, exhausted CD8⁺ T cells are localized in the tumor, and that CPT is enhanced in combination with immune checkpoint blockade (ICB). Addition of ICB using anti-programmed cell death 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibodies resulted in ablation of medium-sized, established KPC tumors (∼200 mm³) without recurrence for over 100 days. Mice rejected subsequent tumor re-challenge. Flow cytometry and tumor slice analysis following injection of a fluorescently labeled anti-PD-1 antibody showed that CPT improved antibody delivery to the tumor microenvironment. Treatment of large established tumors (∼400 mm³) using with CPT and ICB induced appreciable tumor regression and delay in regrowth. Taken together, these data demonstrate the utility of combining CPT with immunotherapies.

Single-treatment tumor ablation with photodynamic liposomal irinotecan sucrosulfate

Irinotecan (IRI) loaded actively into PEGylated liposomes via a sucrosulfate gradient has been approved recently to treat advanced pancreatic cancer. In this study, a similar liposomal composition was developed that includes a low mole fraction (1 mol.%) of porphyrin-phospholipid (PoP), a photosensitizer that stably incorporates into liposomes, to confer light-triggered IRI release. IRI-loaded PoP liposomes containing ammonium sucrosulfate (ASOS) as a complexing agent were more stable in serum compared to liposomes employing the more conventional ammonium sulfate. Without irradiation, PoP IRI liposomes released less than 5% IRI during 8 h of incubation in bovine serum at 37 °C, but released over 90% of the drug within minutes of exposure to red light (665 nm) irradiation. A single treatment with IRI-PoP liposomes and light exposure (15 mg/kg IRI with 250 J/cm2) resulted in tumor eradication in mice bearing either MIA PaCa-2 tumors or low-passage patient-derived tumor xenografts that recapitulate characteristics of the clinical disease. Analogous monotherapies of IRI or photodynamic therapy were ineffective in controlling tumor growth. Enhanced drug uptake could be visualized within laser-treated tumors by direct in situ imaging of irinotecan. Biodistribution analysis of IRI, its active metabolite (SN-38), and major metabolite (SN-38 G) showed that laser treatment significantly increased tumor accumulation of all IRI-derived molecular species. A pharmacokinetic model that hypothesized tumor vasculature permeabilization as the primary reason underlying the increased drug deposition accounted for the enhanced drug influx into tumors.

Enhancing Penetration Ability of Semiconducting Polymer Nanoparticles for Sonodynamic Therapy of Large Solid Tumor

Sonodynamic therapy (SDT) holds growing promise in deep-seated or large solid tumor treatment owing to its high tissue penetration depth ability; however, its therapeutic efficacy is often compromised due to the hypopermeable and hypoxic characteristics in the tumor milieu. Herein, a semiconducting polymer nanoparticle (SPNC) that synergistically enhances tumor penetration and alleviates tumor hypoxia is reported for sonodynamic therapy of large solid tumors. SPNC comprises a semiconducting polymer nanoparticle core as a sonodynamic converter coated with a poly (ethylene glycol) corona. An oxygen-modulating enzyme, catalase, is efficiently conjugated to the surface of nanoparticles via the coupling reaction. Superior to its counterpart SPNCs (SPNC2 (84 nm) and SPNC3 (134 nm)), SPNC with the smallest size (SPNC1 (35 nm)) can efficiently penetrate throughout the tumor interstitium to alleviate whole tumor hypoxia in a large solid tumor model. Upon ultrasound (US) irradiation, SPNC1 can remotely generate sufficient singlet oxygen to eradicate tumor cells at a deep-tissue depth. Such a single treatment of SPNC1-medicated sonodynamic therapy effectively inhibits tumor growth in a large solid tumor mouse model. Therefore, this study provides a generalized strategy to synergistically overcome both poor penetration and hypoxia of large tumors for enhanced cancer treatment.

Two Laser Treatments Can Improve Tumor Ablation Efficiency of Chemophototherapy

Chemophototherapy is an emerging tumor ablation modality that can improve local delivery of chemotherapeutic agents. Long circulating doxorubicin (Dox) in porphyrin-phospholipid (PoP) liposomes (LC-Dox-PoP) has previously been developed as an effective chemophototherapy agent. In the present study, we observed that in mice, LC-Dox-PoP showed enhanced accumulation in human pancreatic tumor xenografts even with suboptimal light doses, as assessed by fluorometric analysis of tissue homogenates and microscopic imaging of Dox and PoP in tumor slices. A second laser treatment, at a time point in which tumors had greater drug accumulation as a result of the first laser treatment, induced potent tumor ablation. Efficacy studies were carried out in two human pancreatic cancer subcutaneous mouse tumor models; MIA PaCa-2 or low-passage patient derived pancreatic cancer xenografts. A single treatment of 3 mg/kg LC-Dox-PoP and an initial 150 J/cm² laser treatment 1 h after drug administration, followed by second laser treatment of 50 J/cm² 8 h after drug administration, was more effective than a single laser treatment of 200 J/cm² at either of those time points. Thus, this study presents proof-of-principle and rationale for using two discrete laser treatments to enhance the efficacy of chemophototherapy.

Injectable drug delivery systems of doxorubicin revisited: In vitro-in vivo relationships using human clinical data

A growing number of nanomedicines entered the clinical trials and improved our understanding of the in vivo responses expected in humans. The in vitro drug release represents an important critical quality attribute involved in pharmacokinetics. Establishing in vitro-in vivo relationships for nanomedicines requires a careful analysis of the clinical data with respect to the unique differences between drugs and nanomedicines. Also, the biorelevant assay must reflect the release mechanism of the carrier. Four drug delivery systems of doxorubicin were evaluated for their in vitro release behavior under biorelevant conditions using the dispersion releaser. The pharmacokinetics observed during the first-in-men clinical trials were analyzed using a custom-made physiologically-based nanocarrier biopharmaceutics model. The drug product Lipodox® and the clinical candidate NanoCore-7.4 were evaluated to validate the model. Afterward, the in vivo performances of the preclinical candidates NanoCore-6.4 and doxorubicin-loaded nano-cellular vesicle technology systems (an extracellular vesicle preparation) were predicted. In vitro and in vivo release were in good correlation as indicated by the coefficients of determination of 0.98648 (NanoCore-7.4) and 0.94107 (Lipodox®). The predictions required an estimation of the carrier half-life in blood circulation leading to considerable uncertainty. Still, the simulations narrow down the possible scenarios in the clinical evaluation of nanomedicines and provide a valuable addition to animal studies.

Optimized Photoactivatable Lipid Nanoparticles Enable Red Light Triggered Drug Release

Encapsulation of small molecule drugs in long-circulating lipid nanoparticles (LNPs) can reduce toxic side effects and enhance accumulation at tumor sites. A fundamental problem, however, is the slow release of encapsulated drugs from these liposomal systems at the disease site resulting in limited therapeutic benefit. Methods to trigger release at specific sites are highly warranted. Here, it is demonstrated that incorporation of ultraviolet (UV-A) or red-light photoswitchable-phosphatidylcholine analogs (AzoPC and redAzoPC) in conventional LNPs generates photoactivatable LNPs (paLNPs) having comparable structural integrity, drug loading capacity, and size distribution to the parent DSPC-cholesterol liposomes. It is shown that 65-70% drug release (doxorubicin) can be induced from these systems by irradiation with pulsed light based on trans-to-cis azobenzene isomerization. In vitro it is confirmed that paLNPs are non-toxic in the dark but convey cytotoxicity upon irradiation in a human cancer cell line. In vivo studies in zebrafish embryos demonstrate prolonged blood circulation and extravasation of paLNPs comparable to clinically approved formulations, with enhanced drug release following irradiation with pulsed light. Conclusively, paLNPs closely mimic the properties of clinically approved LNPs with the added benefit of light-induced drug release making them promising candidates for clinical development.

Thinking outside the macrocycle: Potential biomedical roles for nanostructured porphyrins and phthalocyanines — a SPP/JPP Young Investigator Award paper

Porphyrins and phthalocyanines feature strong light absorption, capacity for metal chelation, and a track record of use in human therapeutic applications. Various conjugates and formulations of these macrocycles have shown potential to forge new applications in the biomedical sciences. Our lab has explored several such approaches including porphyrin polymer hydrogels, porphyrin-lipid nanovesicles, and surfactant-stripped micelles. These all feature in common a high density of tetrapyrroles, as well as unique functional properties. Porphyrin polymer hydrogels with high porphyrin density and bright fluorescence emission were demonstrated for use as a new class of implantable biosensors. Porphyrin-lipid nanovesicles hold potential for phototherapy, imaging, and also drug and vaccine delivery. Surfactant-stripped micelles have been developed for high-contrast photoacoustic imaging. In this ICPP Young Investigator Award brief perspective, we discuss our own efforts on these fronts. Taken together, the results show that tetrapyrroles enable new approaches for tackling biomedical problems and also confirm what was already well-known to members of the Society of Porphyrins and Phthalocyanines: that these molecules are remarkably versatile and enable research to flow in unexpected directions.

Labeling of Erythrocytes by Porphyrin-Phospholipid

A method is developed for membrane labeling of erythrocytes with porphyrin-phospholipid (PoP). To generate a concentrated PoP solution for labeling human red blood cells (RBCs), various surfactants and solvents are screened to identify conditions that avoid hemolysis, while minimizing non-specific PoP co-precipitation with RBCs in the pellet during centrifugation washes. Cholate, Tween 80 and Tween 40 are identified as useful surfactants for this purpose. When labeled RBCs are mixed with unlabeled ones, substantial non-specific PoP exchange is observed. Egg-yolk lecithin is included in a washing buffer to remove loosely bound PoP and reduce PoP exchange with unlabeled erythrocytes, based on flow cytometry and photodynamic hemolysis assays. Murine RBCs that are labeled with ⁶⁴Cu-chelated PoP displayed altered biodistribution with longer blood circulation relative to directly administered ⁶⁴Cu-chelated PoP.

Enhanced antitumour efficiency of R8GD-modified epirubicin plus tetrandrine liposomes in treatment of gastric cancer via inhibiting tumour metastasis

Tumour metastasis is a major cause of cancer treatment failure and death, and chemotherapy efficiency for gastric cancer patients is usually unsatisfactory due to tumour cell metastasis, poor targeting and serious adverse reactions. In this study, a kind of R₈GD-modified epirubicin plus tetrandrine liposomes was prepared to enhance the antitumor efficiency via killing tumour cells, destroying tumour metastasis and inhibiting energy supply for tumour cells. In order to investigate the antitumour efficiency of the targeting liposomes, morphology observation, intracellular uptake, cytotoxic effects, and inhibition on tumour metastasis and energy supply were carried out in vitro, and tumour-bearing mice models were established to investigate the antitumour efficiency in vivo. In vitro results showed that R₈GD-modified epirubicin plus tetrandrine liposomes with ideal physicochemical properties could kill the most tumour cells, inhibit tumour metastasis and cut-off energy supply for tumour cells. In vivo results exhibited that R₈GD-modified epirubicin plus tetrandrine liposomes could enhance the accumulation in tumour site and display an obvious antitumor efficiency. Therefore, R₈GD-modified epirubicin plus tetrandrine liposomes could be used as a potential therapy for treatment of gastric cancer.

Transformable hybrid semiconducting polymer nanozyme for second near-infrared photothermal ferrotherapy

Despite its growing promise in cancer treatment, ferrotherapy has low therapeutic efficacy due to compromised Fenton catalytic efficiency in tumor milieu. We herein report a hybrid semiconducting nanozyme (HSN) with high photothermal conversion efficiency for photoacoustic (PA) imaging-guided second near-infrared photothermal ferrotherapy. HSN comprises an amphiphilic semiconducting polymer as photothermal converter, PA emitter and iron-chelating Fenton catalyst. Upon photoirradiation, HSN generates heat not only to induce cytotoxicity but also to enhance Fenton reaction. The increased ·OH generation promotes both ferroptosis and apoptosis, oxidizes HSN (42 nm) and transforms it into tiny segments (1.7 nm) with elevated intratumoral permeability. The non-invasive seamless synergism leads to amplified therapeutic effects including a deep ablation depth (9 mm), reduced expression of metastasis-related proteins and inhibition of metastasis from primary tumor to distant organs. Thereby, our study provides a generalized nanozyme strategy to compensate both ferrotherapy and phototherapeutics for complete tumor regression.

Due to tumour microenvironment, Fenton reactions have low therapeutic efficiency. Here the authors report on the application of NIR-II hybrid semiconducting nanozymes for combined photothermal therapy and enhanced ferrotherapy with photoacoustic imaging and show application in vivo in tumour models.