Strategies and challenges to improve the performance of tumor-associated active targeting

Research progress of sorafenib drug delivery system in the treatment of hepatocellular carcinoma: An update

Hepatocellular carcinoma (HCC) is one of the most prevalent malignant tumors in the contemporary era, representing a significant global health concern. Early HCC patients have mild symptoms or are asymptomatic, which promotes the onset and progression of the disease. Moreover, advanced HCC is insensitive to chemotherapy, making traditional clinical treatment unable to block cancer development. Sorafenib (SFB) is a first-line targeted drug for advanced HCC patients with anti-angiogenesis and anti-tumor cell proliferation effects. However, the efficacy of SFB is constrained by its off-target distribution, rapid metabolism, and multi-drug resistance. In recent years, nanoparticles based on a variety of materials have been demonstrated to enhance the targeting and therapeutic efficacy of SFB against HCC. Concurrently, the advent of joint drug delivery systems has furnished crucial empirical evidence for reversing SFB resistance. This review will summarize the application of nanotechnology in the field of HCC treatment over the past five years. It will focus on the research progress of SFB delivery systems combined with multiple therapeutic modalities in HCC treatment.

Stealth and Biocompatible Gold Nanoparticles through Surface Coating with a Zwitterionic Derivative of Glutathione

Gold nanoparticles (AuNPs) hold promise in biomedicine, but challenges like aggregation, protein corona formation, and insufficient biocompatibility must be thoroughly addressed before advancing their clinical applications. Designing AuNPs with specific protein corona compositions is challenging, and strategies for corona elimination, such as coating with polyethylene glycol (PEG), have limitations. In this study, we introduce a commercially available zwitterionic derivative of glutathione, glutathione monoethyl ester (GSHzwt), for the surface coating of colloidal AuNPs. Particles coated with GSHzwt were investigated alongside four other AuNPs coated with various ligands, including citrate ions, tiopronin, glutathione, cysteine, and PEG. We then undertook a head-to-head comparison of these AuNPs to assess their behavior in biological fluid. GSHzwt-coated AuNPs exhibited exceptional resistance to aggregation and protein adsorption. The particles could also be readily functionalized with biotin and interact with streptavidin receptors in human plasma. Additionally, they exhibited significant blood compatibility and noncytotoxicity. In conclusion, GSHzwt provides a practical and easy method for the surface passivation of AuNPs, creating "stealth" particles for potential clinical applications.

Targeting Cytotoxic Agents through EGFR-Mediated Covalent Binding and Release

A major drawback of cytotoxic chemotherapy is the lack of selectivity toward noncancerous cells. The targeted delivery of cytotoxic drugs to tumor cells is a longstanding goal in cancer research. We proposed that covalent inhibitors could be adapted to deliver cytotoxic agents, conjugated to the β-position of the Michael acceptor, via an addition-elimination mechanism promoted by covalent binding. Studies on model systems showed that conjugated 5-fluorouracil (5FU) could be released upon thiol addition in relevant time scales. A series of covalent epidermal growth factor receptor (EGFR) inhibitors were synthesized as their 5FU derivatives. Achieving the desired release of 5FU was demonstrated to depend on the electronics and geometry of the compounds. Mass spectrometry and NMR studies demonstrated an anilinoquinazoline acrylate ester conjugate bound to EGFR with the release of 5FU. This work establishes that acrylates can be used to release conjugated molecules upon covalent binding to proteins and could be used to develop targeted therapeutics.

Hsp70-Targeting and Size-Tunable Nanoparticles Combine with PD-1 Checkpoint Blockade to Treat Glioma

Invasive glioma usually disrupts the integrity of the blood-brain barrier (BBB), making the delivery of nanodrugs across the BBB possible, but sufficient targeting ability is still avidly needed to improve drug accumulation in glioma. Membrane-bound heat shock protein 70 (Hsp70) is expressed on the membrane of glioma cells rather than adjacent normal cells, therefore it can serve as a specific glioma target. Meanwhile, prolonging the retention in tumors is important for active-targeting nanoparticles to overcome receptor-binding barriers. Herein, the Hsp70-targeting and acid-triggered self-assembled gold nanoparticles (D-A-DA/TPP) are proposed to realize selective delivery of doxorubicin (DOX) to glioma. In the weakly acidic glioma matrix, D-A-DA/TPP formed aggregates to prolong retention, improve receptor-binding efficiency and facilitate acid-responsive DOX release. DOX accumulation in glioma induced immunogenic cell death (ICD) to promote antigen presentation. Meanwhile, combination with the PD-1 checkpoint blockade further activate T cells and provokes robust anti-tumor immunity. The results showed that D-A-DA/TPP can induce more glioma apoptosis. Furthermore, in vivo studies indicated D-A-DA/TPP plus PD-1 checkpoint blockade significantly improved median survival time. This study offeres a potential nanocarrier combining size-tunable strategy with active targeting ability to increase drug enrichment in glioma and synergizes with PD-1 checkpoint blockade to achieve chemo-immunotherapy.

Lipid nanoparticles (LNPs) for in vivo RNA delivery and their breakthrough technology for future applications

RNA therapeutics show a significant breakthrough for the treatment of otherwise incurable diseases and genetic disorders by regulating disease-related gene expression. The successful development of COVID-19 mRNA vaccines further emphasizes the potential of RNA therapeutics in the prevention of infectious diseases as well as in the treatment of chronic diseases. However, the efficient delivery of RNA into cells remains a challenge, and nanoparticle delivery systems such as lipid nanoparticles (LNPs) are necessary to fully realize the potential of RNA therapeutics. While LNPs provide a highly efficient platform for the in vivo delivery of RNA by overcoming various biological barriers, several challenges remain to be resolved for further development and regulatory approval. These include a lack of targeted delivery to extrahepatic organs and a gradual loss of therapeutic potency with repeated doses. In this review, we highlight the fundamental aspects of LNPs and their uses in the development of novel RNA therapeutics. Recent advances in LNP-based therapeutics and preclinical/clinical studies are overviewed. Lastly, we discuss the current limitations of LNPs and introduce breakthrough technologies that might overcome these challenges in future applications.

Tailoring renal-clearable zwitterionic cyclodextrin for colorectal cancer-selective drug delivery

Although cyclodextrin-based renal-clearable nanocarriers have a high potential for clinical translation in targeted cancer therapy, their designs remain to be optimized for tumour retention. Here we report on the design of a tailored structure for renal-clearable zwitterionic cyclodextrin for colorectal cancer-selective drug delivery. Twenty cyclodextrin derivatives with different charged moieties and spacers are synthesized and screened for colloidal stability. The resulting five candidates are evaluated for biodistribution and an optimized structure is identified. The optimized cyclodextrin shows a high tumour accumulation and is used for delivery of doxorubicin and ulixertinib. Higher tumour accumulation and tumour penetration facilitates tumour elimination. The improved antitumour efficacy is demonstrated in heterotopic and orthotopic colorectal cancer models.

An MMAE-loaded PDL1 active targeting nanomedicine for the precision treatment of colon cancer

Tumor-active-targeting drugs such as antibody-drug conjugates have emerged as promising accurate therapeutic agents. However, their complex preparations risk compromising the targeting ability of the fragment antigen binding (Fab) region and promote aggregation over long-term storage. Here, we propose a tumor-active-targeting nanomedicine, aPDL1-PLG-MMAE, that effectively targets programmed death-ligand 1 (PDL1) high-expressing tumors and delivers monomethyl auristatin E (MMAE). aPDL1-PLG-MMAE consists of an anti-PDL1 monoclonal antibody (aPDL1) and poly(L-glutamic acid) (PLG) grafted Fc-III-4C peptide/Val-Cit-PAB-MMAE (Fc-PLG-MMAE). Fc-PLG-MMAE was obtained by conjugating the Fc-III-4C peptide and Val-Cit-PAB-MMAE to PLG via amide condensation. The strong affinity between the fragment crystallizable (Fc) region of aPDL1 and the Fc-III-4C peptide enabled aPDL1 and Fc-PLG-MMAE to self-assemble into aPDL1-PLG-MMAE after four hours of coincubation in PBS. As this nanomedicine can be quickly prepared for immediate use, the required antibodies can be stored separately from the Fc-PLG-MMAE portion for extended periods, which also facilitates transport. Moreover, aPDL1-PLG-MMAE demonstrated robust tumor recognition and targeting effects on MC38 colon cancer cells, resulting in potent therapeutic efficacy without significant toxicities.

PEGylated Manganese-Zinc Ferrite Nanocrystals Combined with Intratumoral Implantation of Micromagnets Enabled Synergetic Prostate Cancer Therapy via Ferroptotic and Immunogenic Cell Death

Therapeutic efficacy for prostate cancer is highly restricted by insufficient drug accumulation and the resistance to apoptosis and immunogenic cell death (ICD). Although enhanced permeability and retention (EPR) effect of magnetic nanomaterials could benefit from external magnetic field, it falls off rapidly with increased distance from magnet surface. Considering the deep location of prostate in pelvis, the improvement of EPR effect by external magnetic field is limited. In addition, apoptosis resistance and cGAS-STING pathway inhibition-related immunotherapy resistance are major obstacles to conventional therapy. Herein, the magnetic PEGylated manganese-zinc ferrite nanocrystals (PMZFNs) are designed. Instead of providing external magnet, micromagnets into tumor tissues are intratumorally implanted to actively attract and retain intravenously-injected PMZFNs. As a result, PMZFNs accumulate in prostate cancer with high efficacy, depending on the established internal magnetic field, which subsequently elicit potent ferroptosis and the activation of cGAS-STING pathway. Ferroptosis not only directly suppresses prostate cancer but also triggers burst release of cancer-associated antigens and consequently initiates ICD against prostate cancer, where activated cGAS-STING pathway further amplifies the efficacy of ICD by generating interferon-β. Collectively, the intratumorally implanted micromagnets confer a durable EPR effect of PMZFNs, which eventually achieve the synergetic tumoricidal efficacy with negligible systemic toxicity.

A multi-functional nano-system combining PI3K-110α/β inhibitor overcomes P-glycoprotein mediated MDR and improves anti-cancer efficiency

P-glycoprotein (P-gp/ABCB1)-mediated multidrug resistance (MDR) in cancers severely limit chemotherapeutic efficacy. We recently reported that phosphatidylinositol-3-kinase (PI3K) 110α and 110β subunits can be novel targets for reversal of P-gp mediated MDR in cancers, and BAY-1082439 as an inhibitor specific for PI3K 110α and 110β subunits could reverse P-gp-mediated MDR by downregulating P-gp expression in cancer cells. However, BAY-1082439 has very low solubility, short half-life and high in-vivo clearance rate. Till now, nano-system with the functions to target PI3K P110α and P110β and reverse P-gp mediated MDR in cancers has not been reported. In our study, a tumor targeting drug delivery nano-system PBDF was established, which comprised doxorubicin (DOX) and BAY-1082439 respectively encapsulated by biodegradable PLGA-SH nanoparticles (NPs) that were grafted to gold nanorods (Au NRs) modified with FA-PEG-SH, to enhance the efficacy to reverse P-gp mediated MDR and to target tumor cells, further, to enhance the efficiency to inhibit MDR tumors overexpressing P-gp. In-vitro experiments indicated that PBDF NPs greatly enhanced uptake of DOX, improved the activity to reverse MDR, inhibited the cell proliferation, and induced S-phase arrest and apoptosis in KB-C2 cells, as compared with free DOX combining free BAY-1082439. In-vivo experiments further demonstrated that PBDF NPs improved the anti-tumor ability of DOX and inhibited development of KB-C2 tumors. Notably, the metastasis of KB-C2 cells in livers and lungs of nude mice were inhibited by treatment with PBDF NPs, which showed no obvious in-vitro or in-vivo toxicity.

Development of Thiol-Maleimide hydrogels incorporating graphene-based nanomaterials for cancer chemo-photothermal therapy

Nano-sized materials have been widely explored in the biomedicine field, especially due to their ability to encapsulate drugs intended to be delivered to cancer cells. However, systemically administered nanomaterials face several barriers that can hinder their tumor-homing capacity. In this way, researchers are now focusing their efforts in developing technologies that can deliver the nanoparticles directly into the tumor tissue. Particularly, hydrogels assembled using Thiol-Maleimide Michael type additions are emerging for this purpose due to their capacity to incorporate high nanoparticles' doses in a compact 3D structure as well as good chemical selectivity, biocompatibility, and straightforward preparation. Nevertheless, such hydrogels have been mostly prepared using synthetic polymers, which is not ideal due to their poor biodegradability. In this work, a novel natural polymer-based Thiol-Maleimide hydrogel was produced for application in breast cancer chemo-photothermal therapy. To obtain natural polymers compatible with this crosslinking chemistry, Hyaluronic acid was endowed with Thiol groups and deacetylated Chitosan was grafted with Maleimide groups. Parallelly, Doxorubicin loaded Dopamine-reduced graphene oxide (DOX/DOPA-rGO) was prepared for attaining Near Infrared (NIR) light responsive chemo-photothermal nanoagents. By simply mixing Hyaluronic Acid-Thiol, deacetylated Chitosan-Maleimide and DOX/DOPA-rGO, Thiol-Maleimide crosslinked hydrogels incorporating this nanomaterial could be assembled (DOX/DOPA-rGO@TMgel). When breast cancer cells were incubated with DOPA-rGO@TMgel and exposed to NIR light (photothermal therapy), their viability was reduced to about 59 %. On the other hand, DOX/DOPA-rGO@TMgel (chemotherapy) reduced cancer cells' viability to 50 %. In stark contrast, the combined action of DOX/DOPA-rGO@TMgel and NIR light decreased breast cancer cells' viability to just 21 %, highlighting its chemo-photothermal potential.

Small molecules as cancer targeting ligands: Shifting the paradigm

Conventional chemotherapeutics exploration is hampered due to their nonspecific distribution leading to unintended serious toxicity. Toxicity is so severe that deciding to go for chemotherapy becomes a question of concern for many terminally ill cancer patients. However, with evolving times nanotechnology assisted in reducing the haywire distribution and channelizing the movement of drug-enclosing drug delivery systems to cancer cells to a greater extent, yet toxicity issues still could not be obliterated. Thus, active targeting appeared as a refuge, where ligands actively or specifically deliver linked chemotherapeutics and carriers to cancer cells. For a very long time, large molecule weight/macromolecular ligands (peptides and big polymers) were considered the first choice for ligand-directed active cancer targeting, due to their specificity towards overexpressed native cancer receptors. However, complex characterization, instability, and the expensive nature demanded to reconnoitre better alternatives for macromolecule ligands. The concept of small molecules as ligands emerged from the idea that few chemical molecules including chemotherapeutics have a higher affinity for cancer receptors, which are overexpressed on cell membranes, and may have the ability to assist in drug cellular uptake through endocytosis. But now the question is, can they assist the conjugated macro cargos to enter the cell or not? This present review will provide a holistic overview of the small molecule ligands explored till now.

Radiation-assisted strategies provide new perspectives to improve the nanoparticle delivery to tumor

Nanoparticles (NPs), with advantages in tumor targeting, have been extensively developed for anticancer treatment. However, the delivery efficacy of NPs tends to be heterogeneous in clinical research. Surprisingly, a traditional cancer treatment, radiotherapy (radiation), has been observed with the potential to improve the delivery of NPs by influencing the features of the tumor microenvironment, which provides new perspectives to overcome the barriers in the NPs delivery. Since the effect of radiation can also be enhanced by versatile NPs, these findings of radiation-assisted NPs delivery suggest innovative strategies combining radiotherapy with nanotherapeutics. This review summarizes the research on the delivery and therapeutic efficacy of NPs that are improved by radiation, focusing on relative mechanisms and existing challenges and opportunities.

Effects of morphology and size of nanoscale drug carriers on cellular uptake and internalization process: a review

In the field of targeted drug delivery, the effects of size and morphology of drug nanocarriers are of great importance and need to be discussed in depth. To be concise, among all the various shapes of nanocarriers, rods and tubes with a narrow cross-section are the most preferred shapes for the penetration of a cell membrane. In this regard, several studies have focused on methods to produce nanorods and nanotubes with controlled optimized size and aspect ratio (AR). Additionally, a non-spherical orientation could affect the cellular uptake process while a tangent angle of less than 45° is better at penetrating the membrane, and Ω = 90° is beneficial. Moreover, these nanocarriers show different behaviors when confronting diverse cells whose fields should be investigated in future studies. In this survey, a comprehensive classification based on carrier shape is first submitted. Then, the most commonly used methods for control over the size and shape of the carriers are reviewed. Finally, influential factors on the cellular uptake and internalization processes and related analytical methods for evaluating this process are discussed.

Visualization system based on hierarchical targeting for diagnosis and treatment of hepatocellular carcinoma

The accuracy and enrichment rate of targeted drugs largely determine the clinical diagnosis and treatment effect. Therefore, the accuracy and enrichment rate of targeted drugs should be improved. We designed a visual diagnosis and treatment system based on hierarchical targeting. It consists of multifunctional magnetic nanoparticles and a bio magnetic material. Bio-magnet mediated primary targeting can effectively improve the drug enrichment rate in the target tissue. SNF peptide/epithelial cell adhesion molecule antibody mediated targeting liver cancer stem cells (LCSCs) (secondary target) can improve the accuracy of the treatment and its outcomes. Low intensity focused ultrasound irradiation can explode nanoparticles around LCSCs, which can cause physical damage to cells. The combination of released interferon gamma and its receptor (tertiary target) can be used to initiate chemotherapy and immunotherapy. Using the optical properties of Fe₃O₄ and the phase transformation ability of perfluoropentane, the system can enhance photoacoustic and ultrasonic molecular imaging enabling diagnosis and treatment visualization. Targeting LCSCs can accurately provide physical, chemical, and immune treatment of Hepatocellular carcinoma, making the therapeutic effect more effective and thorough. This system may provide a new method for a more accurate visual diagnosis and treatment of tumors.

Dynamic crosslinked polymeric nano-prodrugs for highly selective synergistic chemotherapy

To achieve highly selective synergistic chemotherapy attractive for clinical translation, the precise polymeric nano-prodrugs (PPD-NPs) were successfully constructed via the facile crosslinking reaction between pH-sensitive poly(ortho ester)s and reduction-sensitive small molecule synergistic prodrug (Pt(IV)-1). PPD-NPs endowed the defined structure and high drug loading of cisplatin and demethylcantharidin (DMC). Moreover, PPD-NPs exhibited steady long-term storage and circulation via the crosslinked structure, suitable negative potentials and low critical micelle concentration (CMC), improved selective tumour accumulation and cellular internalization via dynamic size transition and surficial amino protonation at tumoural extracellular pH, promoted efficient disintegration and drug release at tumoural intracellular pH/glutathione, and enhanced cytotoxicity via the synergistic effect between cisplatin and DMC with the feed ratio of 1:2, achieving significant tumour suppression while decreasing the side effects. Thus, the dynamic crosslinked polymeric nano-prodrugs exhibit tremendous potential for clinically targeted synergistic cancer therapy.

Biocompatible Iron Oxide Nanoparticles for Targeted Cancer Gene Therapy: A Review

In recent years, gene therapy has made remarkable achievements in tumor treatment. In a successfully cancer gene therapy, a smart gene delivery system is necessary for both protecting the therapeutic genes in circulation and enabling high gene expression in tumor sites. Magnetic iron oxide nanoparticles (IONPs) have demonstrated their bright promise for highly efficient gene delivery target to tumor tissues, partly due to their good biocompatibility, magnetic responsiveness, and extensive functional surface modification. In this review, the latest progress in targeting cancer gene therapy is introduced, and the unique properties of IONPs contributing to the efficient delivery of therapeutic genes are summarized with detailed examples. Furthermore, the diagnosis potentials and synergistic tumor treatment capacity of IONPs are highlighted. In addition, aiming at potential risks during the gene delivery process, several strategies to improve the efficiency or reduce the potential risks of using IONPs for cancer gene therapy are introduced and addressed. The strategies and applications summarized in this review provide a general understanding for the potential applications of IONPs in cancer gene therapy.

"Targeting Design" of Nanoparticles in Tumor Therapy

Tumor-targeted therapy based on nanoparticles is a popular research direction in the biomedical field. After decades of research and development, both the passive targeting ability of the inherent properties of NPs and the active targeting based on ligand receptor interaction have gained deeper understanding. Unfortunately, most targeted delivery strategies are still in the preclinical trial stage, so it is necessary to further study the biological fate of particles in vivo and the interaction mechanism with tumors. This article reviews different targeted delivery strategies based on NPs, and focuses on the physical and chemical properties of NPs (size, morphology, surface and intrinsic properties), ligands (binding number/force, activity and species) and receptors (endocytosis, distribution and recycling) and other factors that affect particle targeting. The limitations and solutions of these factors are further discussed, and a variety of new targeting schemes are introduced, hoping to provide guidance for future targeting design and achieve the purpose of rapid transformation of targeted particles into clinical application.

Magnetic Nanoparticles: Current Advances in Nanomedicine, Drug Delivery and MRI

Magnetic nanoparticles (MNPs) have evolved tremendously during recent years, in part due to the rapid expansion of nanotechnology and to their active magnetic core with a high surface-to-volume ratio, while their surface functionalization opened the door to a plethora of drug, gene and bioactive molecule immobilization. Taming the high reactivity of the magnetic core was achieved by various functionalization techniques, producing MNPs tailored for the diagnosis and treatment of cardiovascular or neurological disease, tumors and cancer. Superparamagnetic iron oxide nanoparticles (SPIONs) are established at the core of drug-delivery systems and could act as efficient agents for MFH (magnetic fluid hyperthermia). Depending on the functionalization molecule and intrinsic morphological features, MNPs now cover a broad scope which the current review aims to overview. Considering the exponential expansion of the field, the current review will be limited to roughly the past three years.

Advances and applications of monoolein as a novel nanomaterial in mitigating chronic lung diseases

Chronic lung diseases such as asthma, chronic obstructive pulmonary disease, lung cancer, and the recently emerged COVID-19, are a huge threat to human health, and among the leading causes of global morbidity and mortality every year. Despite availability of various conventional therapeutics, many patients remain poorly controlled and have a poor quality of life. Furthermore, the treatment and diagnosis of these diseases are becoming increasingly challenging. In the recent years, the application of nanomedicine has become increasingly popular as a novel strategy for diagnosis, treatment, prevention, as well as follow-up of chronic lung diseases. This is attributed to the ability of nanoscale drug carriers to achieve targeted delivery of therapeutic moieties with specificity to diseased site within the lung, thereby enhancing therapeutic outcomes of conventional therapies whilst minimizing the risks of adverse reactions. For this instance, monoolein is a polar lipid nanomaterial best known for its versatility, thermodynamic stability, biocompatibility, and biodegradability. As such, it is commonly employed in liquid crystalline systems for various drug delivery applications. In this review, we present the applications of monoolein as a novel nanomaterial-based strategy for targeted drug delivery with the potential to revolutionize therapeutic approaches in chronic lung diseases.

Metalated covalent organic frameworks: from synthetic strategies to diverse applications

Covalent organic frameworks (COFs) are a class of organic crystalline porous materials discovered in the early 21st century that have become an attractive class of emerging materials due to their high crystallinity, intrinsic porosity, structural regularity, diverse functionality, design flexibility, and outstanding stability. However, many chemical and physical properties strongly depend on the presence of metal ions in materials for advanced applications, but metal-free COFs do not have these properties and are therefore excluded from such applications. Metalated COFs formed by combining COFs with metal ions, while retaining the advantages of COFs, have additional intriguing properties and applications, and have attracted considerable attention over the past decade. This review presents all aspects of metalated COFs, from synthetic strategies to various applications, in the hope of promoting the continued development of this young field.

Drug Targeting and Nanomedicine: Lessons Learned from Liver Targeting and Opportunities for Drug Innovation

Drug targeting and nanomedicine are different strategies for improving the delivery of drugs to their target. Several antibodies, immuno-drug conjugates and nanomedicines are already approved and used in clinics, demonstrating the potential of such approaches, including the recent examples of the DNA- and RNA-based vaccines against COVID-19 infections. Nevertheless, targeting remains a major challenge in drug delivery and different aspects of how these objects are processed at organism and cell level still remain unclear, hampering the further development of efficient targeted drugs. In this review, we compare properties and advantages of smaller targeted drug constructs on the one hand, and larger nanomedicines carrying higher drug payload on the other hand. With examples from ongoing research in our Department and experiences from drug delivery to liver fibrosis, we illustrate opportunities in drug targeting and nanomedicine and current challenges that the field needs to address in order to further improve their success.

Emerging nanomedicines of paclitaxel for cancer treatment

Malignant tumor is still a leading threat to human health. Despite the rapid development of targeted therapeutic strategies, any treatment specifically acting on single target would inevitably suffer from tumor resistance, largely due to the genetic instability and variability of tumor cells. Thus, traditional therapies such as broad-spectrum chemotherapy would certainly occupy an important position in clinical cancer therapy. Nevertheless, most chemotherapeutic drugs have long been criticized for unsatisfactory therapeutic efficacy with severe off-target toxicity. Although several chemotherapeutic nanomedicines with improved therapeutic safety have been applied in clinics, the therapeutic outcomes still do not fulfill expectation. To address this challenge, enormous efforts have been devoted to developing novel nano-formulations for efficient delivery of chemotherapeutic drugs. Herein, we aim to outline the latest progression in the emerging nanomedicines of paclitaxel (PTX), with special attention to the functional nanocarriers, self-delivering prodrug-nanoassemblies and combination nanotherapeutics of PTX. Finally, the challenges and opportunities of these functional PTX nanomedicines in clinical translation are spotlighted.

Recent advances in targeted nanotherapeutic approaches for breast cancer management

Breast cancer is the most commonly occurring tumor disease worldwide. Breast cancer is currently managed by conventional chemotherapy, which is inadequate in curbing this heterogeneous disease and results in off-site toxic effects, suggesting effective treatment approaches with better therapeutic profiles are needed. This review, therefore, focuses on the recent advancements in delivering therapeutics to the target site using passive and/or active targeted nanodrug-delivery systems to ameliorate endolysosomal escape. In addition, recent strategies in targeting breast cancer stem cells are discussed. The role of naturally cell-secreted nanovesicles (exosomes) in the management of triple-negative breast cancer is also discussed.

Safe and Targeted Sonodynamic Cancer Therapy Using Biocompatible Exosome-Based Nanosonosensitizers

Sonodynamic therapy (SDT), wherein sonosensitizers irradiated with ultrasound (US) produce cytotoxic reactive oxygen species (ROS), has garnered great attention as a promising alternative to photodynamic therapy owing to the significantly increased depth of tissue penetration. The development of nanocarriers that can selectively deposit sonosensitizers into tumor tissues without systemic toxicity is crucial to facilitate the translation of SDT to clinical use. In this study, exosomes, a class of naturally occurring nanoparticles, were utilized as nanocarriers for safe and cancer-targeted delivery of a sonosensitizer, indocyanine green (ICG). The exosomes were surface-engineered with an active cancer-targeting ligand, folic acid (FA), to increase the cancer specificity of the ICG-loaded exosomes (ExoICG). The FA-conjugated, ICG-loaded exosomes (FA-ExoICG) greatly improved aqueous stability and cellular uptake of ICG, resulting in significantly increased ROS generation in breast cancer cells. As a result, the FA-ExoICG demonstrated greater sonotoxicity against cancer cells than ExoICG and free ICG. The in vivo study revealed that compared to ExoICG, more FA-ExoICG accumulated in tumors, and their pharmacokinetic properties were superior. Notably, tumor growth in mice was significantly suppressed, without systemic toxicity, by a single intravenous injection of the FA-ExoICG and subsequent US irradiation. Therefore, this study demonstrated that active cancer-targeted FA-ExoICG could serve as effective nanosonosensitizers for safe and targeted cancer treatment.

Polymeric Nanoparticle Delivery of Combination Therapy with Synergistic Effects in Ovarian Cancer

Treatment of ovarian cancer is challenging due to late stage diagnosis, acquired drug resistance mechanisms, and systemic toxicity of chemotherapeutic agents. Combination chemotherapy has the potential to enhance treatment efficacy by activation of multiple downstream pathways to overcome drug resistance and reducing required dosages. Sequence of delivery and the dosing schedule can further enhance treatment efficacy. Formulation of drug combinations into nanoparticles can further enhance treatment efficacy. Due to their versatility, polymer-based nanoparticles are an especially promising tool for clinical translation of combination therapies with tunable dosing schedules. We review polymer nanoparticle (e.g., micelles, dendrimers, and lipid nanoparticles) carriers of drug combinations formulated to treat ovarian cancer. In particular, the focus on this review is combinations of platinum and taxane agents (commonly used first line treatments for ovarian cancer) combined with other small molecule therapeutic agents. In vitro and in vivo drug potency are discussed with a focus on quantifiable synergistic effects. The effect of drug sequence and dosing schedule is examined. Computational approaches as a tool to predict synergistic drug combinations and dosing schedules as a tool for future nanoparticle design are also briefly discussed.

A paclitaxel and microRNA-124 coloaded stepped cleavable nanosystem against triple negative breast cancer

Background

Triple negative breast cancer (TNBC) is one of the most biologically aggressive breast cancers and lacks effective treatment options, resulting in a poor prognosis. Therefore, studies aiming to explore new therapeutic strategies for advanced TNBC are urgently needed. According to recent studies, microRNA-124 (miR124) not only inhibits tumour growth but also increases the sensitivity of TNBC to paclitaxel (PTX), suggesting that a platform combining PTX and miR124 may be an advanced solution for TNBC.

Results

Herein, we constructed a stepped cleavable calcium phosphate composite lipid nanosystem (CaP/LNS) to codeliver PTX and miR124 (PTX/miR124-NP). PTX/miR124-NP exhibited superior tumor microenvironment responsive ability, in which the surface PEG layer was shed in the mildly acidic environment of tumor tissues and exposed oligomeric hyaluronic acid (o-HA) facilitated the cellular uptake of CaP/LNS by targeting the CD44 receptor on the surface of tumor cells. Inside tumour cells, o-HA detached from CaP/LNS due to the reduction of disulfide bonds by glutathione (GSH) and inhibited tumour metastasis. Then, PTX and miR124 were sequentially released from CaP/LNS and exerted synergistic antitumour effects by reversing the Epithelial-Mesenchymal Transition (EMT) process in MDA-MB-231 cells. Moreover, PTX/miR124-NP showed significant antitumour efficiency and excellent safety in mice bearing MDA-MB-231 tumours.

Conclusion

Based on these results, the codelivery of PTX and miR124 by the CaP/LNS nanosystem might be a promising therapeutic strategy for TNBC.

Molecular Delivery of Cytotoxic Agents via Integrin Activation

Integrins are cell adhesion receptors overexpressed in tumor cells. A direct inhibition of integrins was investigated, but the best inhibitors performed poorly in clinical trials. A gained attention towards these receptors arouse because they could be target for a selective transport of cytotoxic agents. Several active-targeting systems have been developed to use integrins as a selective cell entrance for some antitumor agents. The aim of this review paper is to report on the most recent results on covalent conjugates between integrin ligands and antitumor drugs. Cytotoxic drugs thus conjugated through specific linker to integrin ligands, mainly RGD peptides, demonstrated that the covalent conjugates were more selective against tumor cells and hopefully with fewer side effects than the free drugs.

MRI-traceable theranostic nanoparticles for targeted cancer treatment

Current cancer therapies, including chemotherapy and radiotherapy, are imprecise, non-specific, and are often administered at high dosages - resulting in side effects that severely impact the patient's overall well-being. A variety of multifunctional, cancer-targeted nanotheranostic systems that integrate therapy, imaging, and tumor targeting functionalities in a single platform have been developed to overcome the shortcomings of traditional drugs. Among the imaging modalities used, magnetic resonance imaging (MRI) provides high resolution imaging of structures deep within the body and, in combination with other imaging modalities, provides complementary diagnostic information for more accurate identification of tumor characteristics and precise guidance of anti-cancer therapy. This review article presents a comprehensive assessment of nanotheranostic systems that combine MRI-based imaging (T1 MRI, T2 MRI, and multimodal imaging) with therapy (chemo-, thermal-, gene- and combination therapy), connecting a range of topics including hybrid treatment options (e.g. combined chemo-gene therapy), unique MRI-based imaging (e.g. combined T1-T2 imaging, triple and quadruple multimodal imaging), novel targeting strategies (e.g. dual magnetic-active targeting and nanoparticles carrying multiple ligands), and tumor microenvironment-responsive drug release (e.g. redox and pH-responsive nanomaterials). With a special focus on systems that have been tested in vivo, this review is an essential summary of the most advanced developments in this rapidly evolving field.

pH-Responsive expandable polycarbonate–doxorubicin conjugate nanoparticles for fast intracellular drug release

Nanoparticles with tertiary amines were prepared, which are pH-responsive, expanding to expose the acid-sensitive chemical bond and accelerating drug release.

Lapatinib-loaded acidity-triggered charge switchable polycarbonate-doxorubicin conjugate micelles for synergistic breast cancer chemotherapy

Stimulus-responsive nanosystem is a powerful method to improve the bioavailability and reduce the side effects of anticancer agents. In the present study, a customized dual pH-responsive micellar nanoplatform (DOX+LAP-M) based on polycarbonate-doxorubicin conjugate micelles was prepared to co-deliver the chemotherapeutic agent lapatinib for inhibiting tumor growth and metastasis. DOX+LAP-M micelles with spherical morphology had a size of ~112 nm and had an initial negative surface charge, which are favorable characteristics for long-term circulation in the blood. Once the micelles accumulated in tumor tissues, the intrinsic tumor extracellular acidity triggered the charge switch of DOX+LAP-M micelles from -1 to 9 mV, thereby facilitating cell internalization and tumor penetration. Subsequently, the pH-sensitive micellar core accelerated the release of doxorubicin and lapatinib in the acidic intracellular environment. DOX+LAP-M micelles effectively inhibited the proliferation, migration, and invasion of 4T1 cells in vitro; furthermore, the administration of DOX+LAP-M micelles in 4T1 xenograft-bearing mice suppressed solid tumor growth with an inhibitory rate of 90.2% and significantly decreased pulmonary metastatic nodules, without significant systemic toxicity. This multifunctional micellar system has high potential for clinical cancer therapy.