Pharmacological and physical vessel modulation strategies to improve EPR-mediated drug targeting to tumors

Perfluorocarbon regulates the intratumoural environment to enhance hypoxia-based agent efficacy

Hypoxia-based agents (HBAs), such as anaerobic bacteria and bioreductive prodrugs, require both a permeable and hypoxic intratumoural environment to be fully effective. To solve this problem, herein, we report that perfluorocarbon nanoparticles (PNPs) can be used to create a long-lasting, penetrable and hypoxic tumour microenvironment for ensuring both the delivery and activation of subsequently administered HBAs. In addition to the increased permeability and enhanced hypoxia caused by the PNPs, the PNPs can be retained to further achieve the long-term inhibition of intratumoural O₂ reperfusion while enhancing HBA accumulation for over 24 h. Therefore, perfluorocarbon materials may have great potential for reigniting clinical research on hypoxia-based drugs.

Hypoxia-based agents need permeable and hypoxic intratumour environment to be effective. Here, the authors show that perfluorocarbon nanoparticles promote increased permeability and sustained hypoxia to improve accumulation of hypoxia-based agents, and inhibit intratumour oxygen reperfusion.

Fluorescence Guidance in Surgical Oncology: Challenges, Opportunities, and Translation

Surgical resection continues to function as the primary treatment option for most solid tumors. However, the detection of cancerous tissue remains predominantly subjective and reliant on the expertise of the surgeon. Surgery that is guided by fluorescence imaging has shown clinical relevance as a new approach to detecting the primary tumor, tumor margins, and metastatic lymph nodes. It is a technique to reduce recurrence and increase the possibility of a curative resection. While significant progress has been made in developing this emerging technology as a tool to assist the surgeon, further improvements are still necessary. Refining imaging agents and tumor targeting strategies to be a precise and reliable surgical strategy is essential in order to translate this technology into patient care settings. This review seeks to provide a comprehensive update on the most recent progress of fluorescence-guided surgery and its translation into the clinic. By highlighting the current status and recent developments of fluorescence image-guided surgery in the field of surgical oncology, we aim to offer insight into the challenges and opportunities that require further investigation.

A journey through the emergence of nanomedicines with poly(alkylcyanoacrylate) based nanoparticles

Starting in the late 1970s, the pioneering work of Patrick Couvreur gave birth to the first biodegradable nanoparticles composed of a biodegradable synthetic polymer. These nanoparticles, made of poly(alkylcyanoacrylate) (PACA), were the first synthetic polymer-based nanoparticulate drug carriers undergoing a phase III clinical trial so far. Analyzing the journey from the birth of PACA nanoparticles to their clinical evaluation, this paper highlights their remarkable adaptability to bypass various drug delivery challenges found on the way. At present, PACA nanoparticles include a wide range of nanoparticles that can associate drugs of different chemical nature and can be administered in vivo by different routes. The most recent technologies giving the nanoparticles customised functions could also be implemented on this family of nanoparticles. Through different examples, this paper discusses the seminal role of the PACA nanoparticles' family in the development of nanomedicines.

cRGD-decorated biodegradable polytyrosine nanoparticles for robust encapsulation and targeted delivery of doxorubicin to colorectal cancer in vivo

The clinical success of nanomedicines demands on the development of simple biodegradable nanocarriers that can efficiently and stably encapsulate chemotherapeutics while quickly release the payloads into target cancer cells. Herein, we report that cRGD-decorated biodegradable polytyrosine nanoparticles (cRGD-PTN) boost encapsulation and targeted delivery of doxorubicin (DOX) to colorectal cancer in vivo. The co-assembly of poly(ethylene glycol)-poly(L-tyrosine) (PEG-PTyr) and cRGD-functionalized PEG-PTyr (mol/mol, 80/20) yielded small-sized cRGD-PTN of 70 nm. Interestingly, cRGD-PTN exhibited an ultra-high DOX encapsulation with drug loading contents ranging from 18.5 to 54.1 wt%. DOX-loaded cRGD-PTN (cRGD-PTN-DOX) was highly stable against dilution, serum, and Triton X-100 surfactant, while quickly released DOX in HCT-116 cancer cells, likely resulting from enzymatic degradation of PTyr. Flow cytometry, confocal microscopy and MTT assays displayed that cRGD-PTN-DOX was efficiently internalized into α_vβ₅ overexpressing HCT-116 colorectal cancer cells, rapidly released DOX into the nuclei, and induced several folds better antitumor activity than non-targeted PTN-DOX and clinically used liposomal DOX (Lipo-DOX). SPECT/CT imaging revealed strong tumor accumulation of ¹²⁵I-labeled cRGD-PTN, which was 2.8-fold higher than ¹²⁵I-labeled PTN. Notably, cRGD-PTN-DOX exhibited over 5 times better toleration than Lipo-DOX and significantly more effective inhibition of HCT-116 colorectal tumor than non-targeted PTN-DOX control, affording markedly improved survival rate in HCT-116 tumor-bearing mice with depleting side effects at 6 or 12 mg DOX equiv./kg. cRGD-PTN-DOX with great simplicity, robust drug encapsulation and efficient nucleic drug release appears promising for targeted chemotherapy of colorectal tumor.

pH-Responsive Micelles Assembled by Three-Armed Degradable Block Copolymers with a Cholic Acid Core for Drug Controlled-Release

One of the most famous anticancer drugs, paclitaxel (PTX), has often been used in drug controlled-release studies. The polymers derived from bio-compound bile acids and degradable poly(ε-caprolactone) (PCL) form a reservoir and have been used as a drug delivery system with great advantages. Herein, we grafted poly(N,N-diethylaminoethyl methacrylate) and poly(poly(ethylene glycol) methyl ether methacrylate) into the bile acid-derived three-armed macroinitiator CA-(PCL)₃, resulting in the amphiphilic block copolymers CA-(PCL-b-PDEAEMA-b-PPEGMA)₃. These pH-responsive three-armed block copolymers self-assembled into micelles in aqueous solution and PTX was encapsulated into the micellar core to form PTX-loaded micelles with a drug loading of 29.92 wt %. The micelles were stable in PBS at pH 7.4 and showed a pH-triggered release behavior of PTX under acidic environments, in which 55% of PTX was released at pH 5.0 in 80 h. These cholic acid-based functionalized three-armed block polymers present good biocompatibility, showing great potential for drug controlled-release.

Pharmacokinetics and Pharmacodynamics Modeling and Simulation Systems to Support the Development and Regulation of Liposomal Drugs

Liposomal formulations have been developed to improve the therapeutic index of encapsulated drugs by altering the balance of on- and off-targeted distribution. The improved therapeutic efficacy of liposomal drugs is primarily attributed to enhanced distribution at the sites of action. The targeted distribution of liposomal drugs depends not only on the physicochemical properties of the liposomes, but also on multiple components of the biological system. Pharmacokinetic⁻pharmacodynamic (PK⁻PD) modeling has recently emerged as a useful tool with which to assess the impact of formulation- and system-specific factors on the targeted disposition and therapeutic efficacy of liposomal drugs. The use of PK⁻PD modeling to facilitate the development and regulatory reviews of generic versions of liposomal drugs recently drew the attention of the U.S. Food and Drug Administration. The present review summarizes the physiological factors that affect the targeted delivery of liposomal drugs, challenges that influence the development and regulation of liposomal drugs, and the application of PK⁻PD modeling and simulation systems to address these challenges.

Nanoscale Bupivacaine Formulations To Enhance the Duration and Safety of Intravenous Regional Anesthesia

Intravenous regional anesthesia (IVRA; Bier block) is commonly used to anesthetize an extremity for surgery. Limitations of the procedure include pain from the required tourniquet, the toxicity that can occur from systemic release of local anesthetics, and the lack of postoperative pain relief. We hypothesized that the nanoencapsulation of the local anesthetic would prolong local anesthesia and enhance safety. Here, we developed an ∼15 nm micellar bupivacaine formulation (M-Bup) and tested it in a rat tail vein IVRA model, in which active agents were restricted in the tail by a tourniquet for 15 min. After tourniquet removal, M-Bup provided local anesthesia for 4.5 h, which was two times longer than that from a larger dose of free bupivacaine. Approximately 100 nm liposomal bupivacaine (L-Bup) with the same drug dose as M-Bup did not cause anesthesia. Blood levels of bupivacaine after tourniquet removal were lower in animals receiving M-Bup than L-Bup or free bupivacaine, demonstrating enhanced safety. Tissue reaction to M-Bup was benign.

The effect of cycling hypoxia on MCF-7 cancer stem cells and the impact of their microenvironment on angiogenesis using human umbilical vein endothelial cells (HUVECs) as a model

Background

Breast cancer is the most common type of cancer among females. Hypoxia mediates cancer hallmarks and results from reduced oxygen level due to irregularities in tumor vascularization or when the tumor size prevents oxygen diffusion and triggers angiogenesis to compensate for low oxygen. Cancer stem cells (CSCs) are a rare subpopulation, able to self-renew and to give rise to tumor-initiating cells. It is proposed that CSCs’ secretions help to recruit endothelial cells via angiogenic factors to establish tumor vascularization. In the tumor microenvironment, the effect of hypoxia on CSCs and the impact of their secretions on triggering angiogenesis and tumor vascularization remain questionable. In this study, three-dimensional (3D) CSCs derived from MCF-7 were directly exposed to repetitive long-term cycles of hypoxia to assess its effect on CSCs and then to evaluate the role of the hypoxic CSCs’ (CSCs^HYP) secretions in angiogenesis using (HUVECs) as a model for tumor neovascularization response.

Methods

CSCs derived from MCF-7 cell-line were expanded under repetitive, strictly optimized, long-term/continuous and intermittent hypoxic shots for almost four months to assess hypoxic effect on CSCs, sorted based on CD44⁺/CD24⁻ biomarkers. Hypoxic phenotype of CSCs^HYP was evaluated by assessing the acquired chemoresistance using MTT assay and elevated stemness properties were assessed by flow cytometry. To evaluate the effect of the secretions from CSCs^HYP on angiogenesis, HUVECs were exposed to CSCs^HYP conditioned-medium (CdM)—in which CSCs had been previously grown—to mimic the tumor microenvironment and to assess the effect of the secretions from CSCs^HYP on the HUVECs’ capability of tube formation, migration and wound healing. Additionally, co-culture of CSCs^HYP with HUVECs was performed.

Results

CSCs^HYP acquired higher chemoresistance, increased stemness properties and obtained greater propagation, migration, and wound healing capacities, when compared to CSCs in normoxic condition (CSCs^NOR). HUVECs’ tube formation and migration abilities were mediated by hypoxic (CSCs) conditioned media (CdM).

Discussion

This study demonstrates that chemoresistant and migrational properties of CSCs are enhanced under hypoxia to a certain extent. The microenvironment of CSCs^HYP contributes to tumor angiogenesis and migration. Hypoxia is a key player in tumor angiogenesis mediated by CSCs.

Engineering Nanoparticles for Targeted Remodeling of the Tumor Microenvironment to Improve Cancer Immunotherapy

Owing to the fast-paced growth and cross-infiltration of oncology, immunology and molecular biology, tumor immunotherapy technology represented by immune checkpoint blockade and chimeric antigen receptor (CAR) T cell therapy has lately made remarkable advancements. In comparison with traditional chemotherapy, immunotherapy has the potential to elicit a stronger sustained antitumor immune response in those patients who have advanced malignant malignancies. In spite of the advancements made, a significant number of clinical research works have validated that an extensive proportion of cancer patients still manifest insensitivity to immunotherapy, primarily because of the immunomodulatory interactions between tumor cells and the immunosuppressive tumor microenvironment (TME), together mediating the immune tolerance of tumors and accordingly impacting the positive response to immunotherapy. The intricate immunosuppressive networks formed by stromal cells, inflammatory cells, vasculature, extracellular matrix (ECM), and their secreted cytokines in the TME, play a pivotal role in tumor immune escape. Specific blocking of inhibition pathways in the TME is expected to effectively prevent immune escape and tolerance of tumor cells in addition to their metastasis, accordingly improving the antitumor immune response at various phases of tumor growth. Emerging nanoscale targeted drug carriers truly suit this specific requirement due to their specificity, biocompatibility, and convenience of production. This review emphasizes recent attempts to remodel the tumor immune microenvironment using novel nanoparticles, which include specifically eliminating immunosuppressive cells, reprogramming immune regulatory cells, promoting inflammatory cytokines and blocking immune checkpoints. Targeted remodeling of the immunosuppressive TME using well-designed and fabricated nanoparticles provides a promising strategy for improving the effectiveness of current immunotherapy and is greatly significant.

Combination-Responsive MoO3- x-Hybridized Hyaluronic Acid Hollow Nanospheres for Cancer Phototheranostics

It is of extreme importance to reduce side effects resulting from the nonspecific uptake of phototherapeutic agents by normal tissues. Currently, the single responsive strategy still cannot entirely satisfy the requirements of practical applications. In this study, we developed one kind of combination-responsive phototherapeutic nanoplatforms, where oxygen-deficient molybdenum oxide (MoO_{3- x}) hybridized hyaluronic acid (HA) hollow nanospheres, namely, MoO_{3- x}@HA HNSs, were constructed via a facile one-step method. In MoO_{3- x}@HA HNSs, the reasonable combination of actively targeted specificity endowed by the HA component and tumor microenvironment-responsive phototherapy activity induced by the MoO_{3- x} component can effectively improve the precision of phototherapy. The in vitro and in vivo experimental results confirm that MoO_{3- x}@HA HNSs can selectively kill CD44-overexpressing cancer cells and inhibit tumor growth under an 808 nm laser irradiation, revealing their remarkable synergistic photothermal therapy/photodynamic therapy effect with CD44 receptor-targeted specificity and pH responsiveness in treating cancer. We also prove that MoO_{3- x}@HA HNSs can serve as one kind of contrast agent to achieve the computed tomography/photoacoustic imaging. Encouraged by these results, it is anticipated that the reasonable combination of active targeting and tumor microenvironment responsiveness can be a promising strategy to develop phototherapeutic nanoplatforms for precise multimodality cancer theranostics.

A Promising Biocompatible Platform: Lipid-Based and Bio-Inspired Smart Drug Delivery Systems for Cancer Therapy

Designing new drug delivery systems (DDSs) for safer cancer therapy during pre-clinical and clinical applications still constitutes a considerable challenge, despite advances made in related fields. Lipid-based drug delivery systems (LBDDSs) have emerged as biocompatible candidates that overcome many biological obstacles. In particular, a combination of the merits of lipid carriers and functional polymers has maximized drug delivery efficiency. Functionalization of LBDDSs enables the accumulation of anti-cancer drugs at target destinations, which means they are more effective at controlled drug release in tumor microenvironments (TMEs). This review highlights the various types of ligands used to achieve tumor-specific delivery and discusses the strategies used to achieve the effective release of drugs in TMEs and not into healthy tissues. Moreover, innovative recent designs of LBDDSs are also described. These smart systems offer great potential for more advanced cancer therapies that address the challenges posed in this research area.

RGD-modified polymer and liposome nanovehicles: Recent research progress for drug delivery in cancer therapeutics

Over the past few decades, as the demand for cancer treatment has increased, more rational treatment options (considering size, mode of administration, biocompatibility, efficacy, etc.) and plenty of specifically active targeted nanovehicles have been developed. Integrin receptors targeting are one of the most frequently used approaches because of its highly expressed in cancer cells. In particular, the arginine-glycine-aspartic acid (RGD) peptide and its derivatives have been widely used as ligands for integrin to increase direct targeting capabilies. Polymers as well as liposomes are commonly used as nanovehicles for drug delivery. A variety of work is focused on the RGD-modified polymer and liposome nanovehicles for cancer therapeutics. The goal of this article is to review the published literature in recent years concerning the RGD-modified liposome and polymer nanovehicles to highlight its successful designs for improving cancer therapy and discuss the current challenges as well as the possible development prospects.

Sonopermeation to improve drug delivery to tumors: from fundamental understanding to clinical translation

INTRODUCTION

Ultrasound in combination with microbubbles can make cells and tissues more accessible for drugs, thereby achieving improved therapeutic outcomes. In this review, we introduce the term 'sonopermeation', covering mechanisms such as pore formation (traditional sonoporation), as well as the opening of intercellular junctions, stimulated endocytosis/transcytosis, improved blood vessel perfusion and changes in the (tumor) microenvironment. Sonopermeation has gained a lot of interest in recent years, especially for delivering drugs through the otherwise impermeable blood-brain barrier, but also to tumors.

AREAS COVERED

In this review, we summarize various in vitro assays and in vivo setups that have been employed to unravel the fundamental mechanisms involved in ultrasound-enhanced drug delivery, as well as clinical trials that are ongoing in patients with brain, pancreatic, liver and breast cancer. We summarize the basic principles of sonopermeation, describe recent findings obtained in (pre-) clinical trials, and discuss future directions.

EXPERT OPINION

We suggest that an improved mechanistic understanding, and microbubbles and ultrasound equipment specialized for drug delivery (and not for imaging) are key aspects to create more effective treatment regimens by sonopermeation. Real-time feedback and tools to predict therapeutic outcome and which tumors/patients will benefit from sonopermeation-based interventions will be important to promote clinical translation.

Complex interplay between tumor microenvironment and cancer therapy

Tumor microenvironment (TME) is comprised of cellular and non-cellular components that exist within and around the tumor mass. The TME is highly dynamic and its importance in different stages of cancer progression has been well recognized. A growing body of evidence suggests that TME also plays pivotal roles in cancer treatment responses. TME is significantly remodeled upon cancer therapies, and such change either enhances the responses or induces drug resistance. Given the importance of TME in tumor progression and therapy resistance, strategies that remodel TME to improve therapeutic responses are under developing. In this review, we provide an overview of the essential components in TME and the remodeling of TME in response to anti-cancer treatments. We also summarize the strategies that aim to enhance therapeutic efficacy by modulating TME.

Histidine-rich glycoprotein-induced vascular normalization improves EPR-mediated drug targeting to and into tumors

Tumors are characterized by leaky blood vessels, and by an abnormal and heterogeneous vascular network. These pathophysiological characteristics contribute to the enhanced permeability and retention (EPR) effect, which is one of the key rationales for developing tumor-targeted drug delivery systems. Vessel abnormality and heterogeneity, however, which typically result from excessive pro-angiogenic signaling, can also hinder efficient drug delivery to and into tumors. Using histidine-rich glycoprotein (HRG) knockout and wild type mice, and HRG-overexpressing and normal t241 fibrosarcoma cells, we evaluated the effect of genetically induced and macrophage-mediated vascular normalization on the tumor accumulation and penetration of 10-20 nm-sized polymeric drug carriers based on poly(N-(2-hydroxypropyl)methacrylamide). Multimodal and multiscale optical imaging was employed to show that normalizing the tumor vasculature improves the accumulation of fluorophore-labeled polymers in tumors, and promotes their penetration out of tumor blood vessels deep into the interstitium.

Reduction-sensitive CD44 receptor-targeted hyaluronic acid derivative micelles for doxorubicin delivery

Introduction

A reduction-sensitive CD44-positive tumor-targetable drug delivery system for doxorubicin (DOX) delivery was developed based on hyaluronic acid (HA)-grafted polymers.

Materials and methods

HA was conjugated with folic acid (FA) via a reduction-sensitive disulfide linkage to form an amphiphilic polymer (HA-ss-FA). The chemical structure of HA-ss-FA was analyzed by ultraviolet spectroscopy, Fourier transform infrared spectroscopy, and ¹H nuclear magnetic resonance (NMR) spectroscopy. The molecular weight of HA-ss-FA was determined by high-performance gel permeation chromatography. Blank HA-ss-FA micelles and DOX-loaded micelles were prepared and characterized. The reduction responsibility, cellular uptake, and in vivo biodistribution of HA-ss-FA micelles were investigated.

Results

DOX-loaded micelles were of high encapsulation efficiency (88.09%), high drug-loading content (22.70%), appropriate mean diameter (100-120 nm), narrow size distribution, and negative zeta potential (-6.7 to -31.5 mV). The DOX release from the micelles was significantly enhanced in reduction environment compared to normal environment. The result of in vitro cytotoxicity assay indicated that the blank micelles were of low toxicity and good biocompatibility and the cell viabilities were >100% with the concentration of HA-ss-FA from 18.75 to 600.00 μg/mL. Cellular uptake and in vivo biodistribution studies showed that DOX-loaded micelles were tumor-targetable and could significantly enhance cellular uptake by CD44 receptor-mediated endocytosis, and the cellular uptake of DOX in CD44-positve A549 cells was 1.6-fold more than that in CD44-negative L02 cells. In vivo biodistribution of HA-ss-FA micelles showed that micelles were of good in vivo tumor targetability and the fluorescence of indocyanine green (ICG)-loaded micelles was 4- to 6.6-fold stronger than free ICG within 6 h in HCCLM3 tumor-bearing nude mice.

Conclusion

HA-ss-FA is a promising nanocarrier with excellent biocompatibility, tumor targetability, and controlled drug release capability for delivery of chemotherapy drugs in cancer therapy.

Current Trends and Challenges in the Clinical Translation of Nanoparticulate Nanomedicines: Pathways for Translational Development and Commercialization

The use of nanotechnology in medicine has the potential to have a major impact on human health for the prevention, diagnosis, and treatment of diseases. One particular aspect of the nanomedicine field which has received a great deal of attention is the design and development of nanoparticulate nanomedicines (NNMs) for drug delivery (i.e., drug-containing nanoparticles). NNMs are intended to deliver drugs via various mechanisms: solubilization, passive targeting, active targeting, and triggered release. The NNM approach aims to increase therapeutic efficacy, decrease the therapeutically effective dose, and/or reduce the risk of systemic side effects. In order to move a NNM from the bench to the bedside, several experimental challenges need to be addressed. This review will discuss the current trends and challenges in the clinical translation of NNMs as well as the potential pathways for translational development and commercialization. Key issues related to the clinical development of NNMs will be covered, including biological challenges, large-scale manufacturing, biocompatibility and safety, intellectual property (IP), government regulations, and overall cost-effectiveness in comparison to current therapies. These factors can impose significant hurdles limiting the appearance of NNMs on the market, irrelevant of whether they are therapeutically beneficial or not.

Potential Applications of Nanotechnology in Urological Cancer

Nowadays, the potential scope of nanotechnology in uro-oncology (cancers of the prostate, bladder, and kidney) is broad, ranging from drug delivery, prevention, and diagnosis to treatment. Novel drug delivery methods using magnetic nanoparticles, gold nanoparticles, and polymeric nanoparticles have been investigated in prostate cancer. Additionally, renal cancer treatment may be profoundly influenced by applications of nanotechnology principles. Various nanoparticle-based strategies for kidney cancer therapy have been proposed. Partly due to the dilution of drug concentrations by urine production, causing inadequate drug delivery to tumor cells in the treatment of bladder cancer, various multifunctional bladder-targeted nanoparticles have been developed to enhance therapeutic efficiency. In each of these cancer research fields, nanotechnology has shown several advantages over widely used traditional methods. Different types of nanoparticles improve the solubility of poorly soluble drugs, and multifunctional nanoparticles have good specificity toward prostate, renal, and bladder cancer. Moreover, nanotechnology can also combine with other novel technologies to further enhance effectivity. As our understanding of nanotechnologies grows, additional opportunities to improve the diagnosis and treatment of urological cancer are excepted to arise. In this review, we focus on nanotechnologies with potential applications in urological cancer therapy and highlight clinical areas that would benefit from nanoparticle therapy.

A polypeptide based podophyllotoxin conjugate for the treatment of multi drug resistant breast cancer with enhanced efficiency and minimal toxicity

Podophyllotoxin (PPT) is a chemotherapeutic agent which has shown significant activity against P-glycoprotein (P-gp) mediated multi drug resistant cancer cells. However, because of the poor aqueous solubility and high toxicity, PPT cannot be used in clinical cancer therapy. In order to enhance the efficiency and reduce side effect of PPT, a polypeptide based PPT conjugate PLG-g-mPEG-PPT was developed and used for the treatment of multi drug resistant breast cancer. The PLG-g-mPEG-PPT was prepared by conjugating PPT to poly(l-glutamic acid)-g-methoxy poly(ethylene glycol) (PLG-g-mPEG) via ester bonds. The PPT conjugates self-assembled into nanoparticles with average sizes about 100 nm in aqueous solution. Western blotting assay showed that the PLG-g-mPEG-PPT could effectively inhibit the expression of P-gp in the multiple drug resistant MCF-7/ADR cells. In vitro cytotoxicity assay indicated that the resistance index (RI) values of PLG-g-mPEG-PPT on different drug-resistant cancer cell lines exhibited 57-270 folds reduction than of traditional microtubule inhibitor chemotherapeutic drug PTX or DTX. Hemolysis assay demonstrated that the conjugation greatly decreased the hemolytic activity of free PPT. Maximum tolerated dose (MTD) of PLG-g-mPEG-PPT increased greatly (13.3 folds) as compared to that of free PPT. In vivo study showed that the PLG-g-mPEG-PPT conjugate remarkably enhanced the antitumor efficacy against MCF-7/ADR xenograft tumors with a tumor suppression rate (TSR) of 82.5%, displayed significantly improved anticancer efficacy as compared to free PPT (TSR = 37.1%) with minimal toxicity when both of the two formulations were used in MTD.

STATEMENT OF SIGNIFICANCE

The development of multiple drug resistance (MDR) of cancer cells is the main cause of chemotherapy failure. The over-expression of P-glycoprotein (P-gp) has been recognized to be the most important cause of MDR in cancer. Podophyllotoxin (PPT) is a chemotherapeutic agent which has shown strong activity against P-gp mediated multidrug resistant cancer cells by simultaneously inhibiting the over-expression of P-gp and the growth of cancer cells. However, PPT can not be used in clinical cancer treatment due to its poor aqueous solubility and high toxicity. Herein, we developed a polypeptide based PPT conjugate PLG-g-mPEG-PPT by conjugating PPT to poly(l-glutamic acid)-g-methoxy poly(ethylene glycol). The PLG-g-mPEG-PPT shows significantly decreased hemolytic activity, greatly improved maximum tolerated dose and remarkably enhanced antitumor efficacy against MCF-7/ADR xenograft tumors as compared to free PPT.

CD44 targeted PLGA nanomedicines for cancer chemotherapy

In recent years scientific community has drawn a great deal of attention towards understanding the enigma of cluster of differentiation-44 (CD44) in order to deliver therapeutic agents more selectively towards tumor tissues. Moreover, its over-expression in variety of solid tumors has attracted drug delivery researchers to target this receptor with nanomedicines. Conventional nanomedicines based on biodegradable polymers such as poly(lactide-co-glycolide) (PLGA) are often associated with insufficient cellular uptake by cancer cells, due to lack of active targeting moiety on their surface. Therefore, to address this limitation, CD44 targeted PLGA nanomedicines has gained considerable interest for enhancing the efficacy of chemotherapeutic agents. In this review, we have elaborately discussed the recent progress in the design and synthesis of CD44 targeted PLGA nanomedicines used to improve tumor-targeted drug delivery. We have also discussed strategies based on co-targeting of CD44 with other targeting moieties such as folic acid, human epidermal growth factor 2 (HER2), monoclonal antibodies using PLGA based nanomedicines.

Use of nano engineered approaches to overcome the stromal barrier in pancreatic cancer

While chemotherapy is the only approved non-surgical option for the majority of pancreatic cancer patients, it rarely results in a cure. The failure to respond to chemotherapy is due to the presence of an abundant dysplastic stroma that interferes in drug delivery and as a result of drug resistance. It is appropriate, therefore, to consider the stromal contribution to the resistance to chemotherapy and sidestepping this barrier with nanocarriers that improve survival outcome. In this paper, we provide a short overview of the role of the stroma in chemotherapy resistance, including the use of nanocarriers to negate this barrier. We provide a perspective and guidance towards the implementation of nanotherapeutic approaches to improve therapeutic delivery and efficacy of PDAC management.

Tumor targeting via EPR: Strategies to enhance patient responses

The tumor accumulation of nanomedicines relies on the enhanced permeability and retention (EPR) effect. In the last 5-10 years, it has been increasingly recognized that there is a large inter- and intra-individual heterogeneity in EPR-mediated tumor targeting, explaining the heterogeneous outcomes of clinical trials in which nanomedicine formulations have been evaluated. To address this heterogeneity, as in other areas of oncology drug development, we have to move away from a one-size-fits-all tumor targeting approach, towards methods that can be employed to individualize and improve nanomedicine treatments. To this end, efforts have to be invested in better understanding the nature, the complexity and the heterogeneity of the EPR effect, and in establishing systems and strategies to enhance, combine, bypass and image EPR-based tumor targeting. In the present manuscript, we summarize key studies in which these strategies are explored, and we discuss how these approaches can be employed to enhance patient responses.

Cerasomes and Bicelles: Hybrid Bilayered Nanostructures With Silica-Like Surface in Cancer Theranostics

Over years, theranostic nanoplatforms have provided a new avenue for the diagnosis and treatment of various cancer types. To this end, a myriad of nanocarriers such as polymeric micelles, liposomes, and inorganic nanoparticles (NPs) with distinct physiochemical and biological properties are routinely investigated for preclinical and clinical studies. So far, liposomes have received great attention for various biomedical applications, however, it still suffers from insufficient morphological stability. On the other hand, inorganic NPs depicting excellent therapeutic ability have failed to address biocompatibility issues. This has raised a serious concern about the clinical approval of multifunctional organic or inorganic-based theranostic agents. Recently, partially silica coated nanohybrids such as cerasomes and bicelles demonstrating both diagnostic and therapeutic ability in a single system, have drawn profound attention as a fascinating novel drug delivery system. Compared with traditional liposomal or inorganic-based nanoformulations, this new and highly stable nanocarriers integrates the functional attributes of biomimetic liposomes and silica NPs, therefore, synergize strengths and functions, or even surpass weaknesses of individual components. This review at its best enlightens the emerging concept of such partially silica coated nanohybrids, fabrication strategies, and theranostic opportunities to combat cancer and related diseases.

Indocyanine green conjugated lipid microbubbles as an ultrasound-responsive drug delivery system for dual-imaging guided tumor-targeted therapy

Herein, a multifunctional traceable and ultrasound-responsive drug targeted delivery system based on indocyanine green (ICG) and folic acid (FA) covalently conjugated lipid microbubbles (ILMBs–FA) is proposed. After encapsulation of the anticancer drug resveratrol (RV), the composite (RILMBs–FA) with fluorescence and ultrasound imaging capacity was studied for highly sensitive dual-imaging guided tumor targeted therapy. The resulting RILMBs–FA with an average particle size of 1.32 ± 0.14 μm exhibited good stability and biocompatibility characteristics. The RILMBs–FA featured a high RV loading ratio and the encapsulated RV has been demonstrated to be released from the microbubbles triggered by ultrasound (US) waves. In addition, it was found that the linked FA could facilitate a high cellular uptake of RILMBs–FA via the FA receptor-mediated endocytosis pathway. Compared to free RV and RILMBs, RILMBs–FA with US irradiation demonstrated a more significant tumor cell-killing efficacy mediated by apoptosis in vitro. Eight hours post intravenous injection of RILMBs–FA, the composites showed maximum accumulation in tumorous tissues according to in vivo fluorescence and US images. This ultimately led to the best tumor inhibition effect among all tested drugs under US irradiation. In vivo biosafety evaluations showed that RILMBs–FA featured high biocompatibility characteristics and no significant systemic toxicity over the course of one month. Taken in concert, these results demonstrate the versatility of this drug delivery system with dual-imaging and ultrasound-triggered drug release characteristics for potential future applications in cancer theranostics.

Schematic representation of the synthesis of RILMBs–FA and application in tumor therapy.

Lipid nanoemulsion passive tumor accumulation dependence on tumor stage and anatomical location: a new mathematical model for in vivo imaging biodistribution studies

Nanoparticle delivery to tumor tissue is one of the most important applications of nanomedicine.