A folate modified pH sensitive targeted polymeric micelle alleviated systemic toxicity of doxorubicin (DOX) in multi-drug resistant tumor bearing mice

Smart nanoparticles for cancer therapy

Smart nanoparticles, which can respond to biological cues or be guided by them, are emerging as a promising drug delivery platform for precise cancer treatment. The field of oncology, nanotechnology, and biomedicine has witnessed rapid progress, leading to innovative developments in smart nanoparticles for safer and more effective cancer therapy. In this review, we will highlight recent advancements in smart nanoparticles, including polymeric nanoparticles, dendrimers, micelles, liposomes, protein nanoparticles, cell membrane nanoparticles, mesoporous silica nanoparticles, gold nanoparticles, iron oxide nanoparticles, quantum dots, carbon nanotubes, black phosphorus, MOF nanoparticles, and others. We will focus on their classification, structures, synthesis, and intelligent features. These smart nanoparticles possess the ability to respond to various external and internal stimuli, such as enzymes, pH, temperature, optics, and magnetism, making them intelligent systems. Additionally, this review will explore the latest studies on tumor targeting by functionalizing the surfaces of smart nanoparticles with tumor-specific ligands like antibodies, peptides, transferrin, and folic acid. We will also summarize different types of drug delivery options, including small molecules, peptides, proteins, nucleic acids, and even living cells, for their potential use in cancer therapy. While the potential of smart nanoparticles is promising, we will also acknowledge the challenges and clinical prospects associated with their use. Finally, we will propose a blueprint that involves the use of artificial intelligence-powered nanoparticles in cancer treatment applications. By harnessing the potential of smart nanoparticles, this review aims to usher in a new era of precise and personalized cancer therapy, providing patients with individualized treatment options.

Advances in Polymeric Colloids for Cancer Treatment

Polymer colloids have remarkable features and are gaining importance in many areas of research including medicinal science. Presently, the innovation of cancer drugs is at the top in the world. Polymer colloids have been used as drug delivery and diagnosis agents in cancer treatment. The polymer colloids may be of different types such as micelles, liposomes, emulsions, cationic carriers, and hydrogels. The current article describes the state-of-the-art polymer colloids for the treatment of cancer. The contents of this article are about the role of polymeric nanomaterials with special emphasis on the different types of colloidal materials and their applications in targeted cancer therapy including cancer diagnoses. In addition, attempts are made to discuss future perspectives. This article will be useful for academics, researchers, and regulatory authorities.

Octenyl-succinylated inulins for the delivery of hydrophobic drug

The efficacy of hydrophobic anticancer drugs is limited by their poor solubility in water, inefficient target delivery, and toxic side effects. In this work, doxorubicin (DOX) was solubilized using OSA-inulins which created micellar aggregates in aqueous solution above a critical concentration. In vitro delivery of OSA-inulin-DOX micelles resulted in strong inhibition of the growth of MCF-7 breast cancer cells as compared to free DOX. They also displayed a faster cellular uptake rate, indicating that the micelles were promptly internalized into the cells through CD44 receptor-mediated endocytosis. During in vivo tumor suppression experiments in tumor-bearing mice, the OSA-inulin-DOX micelles strongly hindered tumor growth and showed substantially lower systemic toxicity compared with free DOX. Our achievements demonstrate that OSA-inulin has great potential for the encapsulating, dissolving, and targeted delivery of hydrophobic drugs, especially antitumor drugs, for nutraceutical, medical, and pharmaceutical applications.

Tumor-targeted/reduction-triggered composite multifunctional nanoparticles for breast cancer chemo-photothermal combinational therapy

Breast cancer has become the most commonly diagnosed cancer type in the world. A combination of chemotherapy and photothermal therapy (PTT) has emerged as a promising strategy for breast cancer therapy. However, the intricacy of precise delivery and the ability to initiate drug release in specific tumor sites remains a challenging puzzle. Therefore, to ensure that the therapeutic agents are synchronously delivered to the tumor site for their synergistic effect, a multifunctional nanoparticle system (PCRHNs) is developed, which is grafted onto the prussian blue nanoparticles (PB NPs) by reduction-responsive camptothecin (CPT) prodrug copolymer, and then modified with tumor-targeting peptide cyclo(Asp-d-Phe-Lys-Arg-Gly) (cRGD) and hyaluronic acid (HA). PCRHNs exhibited nano-sized structure with good monodispersity, high load efficiency of CPT, triggered CPT release in response to reduction environment, and excellent photothermal conversion under laser irradiation. Furthermore, PCRHNs can act as a photoacoustic imaging contrast agent-guided PTT. In vivo studies indicate that PCRHNs exhibited excellent biocompatibility, prolonged blood circulation, enhanced tumor accumulation, allow tumor-specific chemo-photothermal therapy to achieve synergistic antitumor effects with reduced systemic toxicity. Moreover, hyperthermia-induced upregulation of heat shock protein 70 in the tumor cells could be inhibited by CPT. Collectively, PCRHNs may be a promising therapeutic way for breast cancer therapy.

GRP78-targeted and doxorubicin-loaded nanodroplets combined with ultrasound: a potential novel theranostics for castration-resistant prostate cancer

The construction of multifunctional oncotherapy nanoplatforms that combine diagnosis and treatment remains challenging. Nanodroplets (NDs), which simultaneously enhance ultrasound imaging and therapeutic effects, are a potential strategy for non-invasive drug delivery. To achieve the goals of precise medicine, novel SP94 peptide-modified and doxorubicin-loaded ultrasonic NDs (SP94-DOX-NDs) for castration-resistant prostate cancer (CRPC) targeting and treatment were constructed in this study. The characteristics, contrast-enhanced ultrasound imaging (CEUI), targeting ability to glucose-regulated protein 78 (GRP78)-overexpressing CRPC and anticancer effect of the SP94-DOX-NDs were assessed. The desired SP94-NDs were successfully prepared using the nanoemulsification method using a certain proportion of SP94-PEG-chitosan, perfluoropentane (PFP), Tween 20, and lecithin. SP94-NDs with a size of ∼300 nm showed great biocompatibility and CEUI ability. Compared with blank NDs, SP94-NDs exhibited higher tumor-specific targeting ability due to conjugation between the SP94 peptide and GRP78-overexpressing 22RV1 cells. Most importantly, in vitro and in vivo investigations showed that SP94-DOX-NDs combined with ultrasound could specifically deliver DOX into 22RV1 cells and thereby demonstrated a stronger anticancer effect than DOX-NDs and DOX. Thus, SP94-DOX-NDs may provide an efficient approach for the real-time imaging of tumors and triggered, accurate drug delivery to tumors.

Co-delivery of the autophagy inhibitor si-Beclin1 and the doxorubicin nano-delivery system for advanced prostate cancer treatment

Resistance to apoptosis is a key mechanism underlying how cancer cells evade tumor therapy. Autophagy can prevent anticancer drug-induced apoptosis and promote tumor resistance. The purpose of this study was to improve the sensitivity and efficacy of chemotherapeutic drugs through the inhibition of autophagy. Hydrophobic doxorubicin-hydrazone-caproyl-maleimide (DOX-EMCH) and autophagy-inhibiting si-Beclin1 were simultaneously delivered via the amphiphilic peptide micelle system (Co-PMs) using poly(L-arginine)-poly(L-histidine)-DOX-EMCH as the copolymer building unit. The constructed micelle system promoted the escape of si-Beclin1 from endosomes and the release of DOX into the nucleus. The Co-PMs exhibited 2.7-fold higher cytotoxicity and proapoptotic ability in PC3 cells than DOX treatment alone, demonstrating that si-Beclin1 could inhibit the autophagic activity of prostate cancer (PCa) cells by targeting the type III PI3K pathway and enhance the sensitivity of the cells to the chemotherapeutic drug DOX. In addition, the peptide micelles successfully passively targeted DOX and si-Beclin1 to the tumor tissue. Compared with DOX or si-Beclin1 treatment alone, the Co-PMs showed a 3.4-fold greater tumor inhibitory potential in vivo, indicative of a significant antiproliferative effect. Our results suggested that the Co-PMs developed in this study have the potential to combine autophagy inhibition and chemotherapy in cancer treatment, especially for PCa.

Tumor Microenvironment Modulation Platform Based on Composite Biodegradable Bismuth-Manganese Radiosensitizer for Inhibiting Radioresistant Hypoxic Tumors

Solid tumors possess a unique internal environment with high-level thiols (mainly glutathione), over-expressed H₂ O₂ , and low oxygen partial pressure, which severely restrict the radiotherapy (RT) efficacy. To overcome the imperfections of RT alone, there is vital to design a multifunctional radiosensitizer that simultaneously achieves multimodal therapy and tumor microenvironment (TME) regulation. Bismuth (Bi)-based nanospheres are wrapped in the MnO₂ layer to form core-shell-structured radiosensitizer (Bi@Mn) that can effectively load docetaxel (DTX). The solubility of Bi@Mn-DTX is further improved via folic acid-modified amphiphilic polyethylene glycol (PFA). Bi@Mn-DTX-PFA can specifically respond to the TME to realize multimodal therapy. Primarily, the outer MnO₂ layer responds with H₂ O₂ and glutathione to release oxygen and generate •OH, thereby alleviating hypoxia and achieving chemodynamic therapy (CDT). Afterward, the strong coordination between Bi³⁺ and deprotonated thiol groups in glutathione allows the mesoporous Bi-containing core bonding with glutathione to form a water-soluble complex. These actions conduce Bi@Mn-DTX-PFA degradation, further releasing DTX to implement chemotherapy (CHT). In addition, the degradation in vivo and tumor enrichment of Bi@Mn-PFA are explored via T₁ -weighted magnetic resonance and computed tomography imaging. The biodegradable composite Bi@Mn-DTX-PFA can simultaneously modulate the TME and achieve multimodal treatment (RT/CDT/CHT) for hypoxic tumors.

Drug Resistance in Metastatic Breast Cancer: Tumor Targeted Nanomedicine to the Rescue

Breast cancer, specifically metastatic breast, is a leading cause of morbidity and mortality in women. This is mainly due to relapse and reoccurrence of tumor. The primary reason for cancer relapse is the development of multidrug resistance (MDR) hampering the treatment and prognosis. MDR can occur due to a multitude of molecular events, including increased expression of efflux transporters such as P-gp, BCRP, or MRP1; epithelial to mesenchymal transition; and resistance development in breast cancer stem cells. Excessive dose dumping in chemotherapy can cause intrinsic anti-cancer MDR to appear prior to chemotherapy and after the treatment. Hence, novel targeted nanomedicines encapsulating chemotherapeutics and gene therapy products may assist to overcome cancer drug resistance. Targeted nanomedicines offer innovative strategies to overcome the limitations of conventional chemotherapy while permitting enhanced selectivity to cancer cells. Targeted nanotheranostics permit targeted drug release, precise breast cancer diagnosis, and importantly, the ability to overcome MDR. The article discusses various nanomedicines designed to selectively target breast cancer, triple negative breast cancer, and breast cancer stem cells. In addition, the review discusses recent approaches, including combination nanoparticles (NPs), theranostic NPs, and stimuli sensitive or “smart” NPs. Recent innovations in microRNA NPs and personalized medicine NPs are also discussed. Future perspective research for complex targeted and multi-stage responsive nanomedicines for metastatic breast cancer is discussed.

Hyaluronic acid functionalized biodegradable mesoporous silica nanocomposites for efficient photothermal and chemotherapy in breast cancer

Chemotherapy is one of conventional treatment methods for breast cancer, but drug toxicity and side effects have severely limited its clinical applications. Photothermal therapy has emerged as a promising method that, upon combination with chemotherapy, can better treat breast cancer. In this context, a biodegradable mesoporous silica nanoparticle (bMSN NPs) system was developed for loading doxorubicin (DOX) and IR780, to be potentially applied in the treatment of breast cancer. IR780 is encapsulated in the pores of bMSN NPs by hydrophobic adsorption, while DOX is adsorbed on the surface of the bMSN NPs by hyaluronic acid electrostatically, to form the bMID NPs. Transmission electron microscopy, fluorescence spectrum and UV absorption spectrum are used to prove the successful encapsulation of IR780 and the loading of DOX. In vitro experiments have shown bMID NPs present an excellent therapeutic effect on breast cancer cells. In vivo fluorescence imaging results have indicated that bMID NPs can accumulate in tumor sites gradually and achieve in vivo long-term circulation and continuous drug release. Furthermore, bMID NPs have provided obvious antitumor effects in breast cancer mouse models, thus evolving as an efficient platform for breast cancer therapy.

Robust fluorescent amphiphilic polymer micelle for drug carrier application

The prepared micelles DPOA possessed good biocompatibility, robust stability, and high fluorescent property. The introduction of fluorescent dye made the amphiphilic copolymer obtain the ability of bioimaging to monitor the transport of drug carriers.

Nanozyme-Incorporated Biodegradable Bismuth Mesoporous Radiosensitizer for Tumor Microenvironment-Modulated Hypoxic Tumor Thermoradiotherapy

Solid tumors inevitably develop radioresistance due to low oxygen partial pressure in the tumor microenvironment. Despite numerous attempts, there are still few effective ways to avoid the hypoxia-induced poor radiotherapeutic effect. To overcome this problem, platinum (Pt) nanodots were fabricated into a mesoporous bismuth (Bi)-based nanomaterial to construct a biodegradable nanocomposite BiPt-folic acid-modified amphiphilic polyethylene glycol (PFA). BiPt-PFA could act as a radiosensitizer to enhance the absorption of X-rays at the tumor site and simultaneously trigger response behaviors related to the tumor microenvironment due to the enrichment of materials in the tumor area. During this process, the Bi-based component consumed glutathione via coordination, thus altering the oxidative stress balance, while Pt nanoparticles catalyzed the decomposition of hydrogen peroxide to generate oxygen, thereby relieving tumor hypoxia. Both Pt and Bi thus co-modulated the tumor microenvironment to improve the radiotherapeutic effect. In addition, Pt dots in BiPt-PFA had strong near-infrared absorption ability and created an intensive photothermal therapeutic effect. Modulation of the tumor microenvironment could thus improve the therapeutic effect in hypoxic tumors by a combination of photothermal therapy and enhanced radiotherapy. BiPt-PFA, as a biodegradable nanocomposite, may thus modulate the tumor microenvironment to enhance the hypoxic tumor therapeutic effect by thermoradiotherapy.

New insights into Hexakis macrocycles as a novel nano-carrier for highly potent anti-cancer treatment: A new challenge in drug delivery

The purpose of this study is to design and evaluate a new tubular assembly structure of Hexakis (m-phenylene ethynylene) (m-PE) macrocycles and to explore its potential application as an innovative drug delivery system. First, we focused on how (m-PE) macrocycles can be self-assembled in both chloroform (CHCl₃) and water solvents for the formation of the assembled nanotube using molecular dynamics (MD) simulations. In contrast to their behavior in water solvent, all ten (m-PE) macrocycles remain aggregated at low concentrations of CHCl₃. We found that these macrocycles carrying chiral side chains and capable of H-bonded self-association, assemble into tubular stacks. Then, the dual delivery strategy for the transport of doxorubicin (DOX) and curcumin (Cur) on the self-assembly system of hexakis (m-PE) nanocarrier is examined using molecular dynamics (MD) simulation and free energy calculation. The obtained results indicated that the binding energy of DOX (- 298.9 kJ/mol) on hexakis (m-PE) in the presence of Cur is higher than free DOX (- 247.7 kJ/mol). Furthermore, in the interaction of the DOX and hexakis m-PE, the contribution of van der Walls (vdW) energy is higher than electrostatic (elec) energy, which can be related to the strong π-π interactions between the drug molecules with the carrier surface. In general, the results indicated that the simultaneous delivery of DOX and Cur through DOX/Cur/hexakis (m-PE) could be a promising vehicle in tumor therapy. Based on the obtained results of the present research, hexakis (m-PE) macrocycle can be used as a drug delivery vehicle for targeted or systemic delivery.

Development of stimuli-responsive intelligent polymer micelles for the delivery of doxorubicin

Doxorubicin is still used as a first-line drug in current therapeutics for numerous types of malignant tumours (including lymphoma, transplantable leukaemia and solid tumour). Nevertheless, to overcome the serious side effects like cardiotoxicity and myelosuppression caused by effective doses of doxorubicin remains as a world-class puzzle. In recent years, the usage of biocompatible polymeric nanomaterials to form an intelligently sensitive carrier for the targeted release in tumour microenvironment has attracted wide attention. These different intelligent polymeric micelles (PMs) could change the pharmacokinetics process of drugs or respond in the special microenvironment of tumour site to maximise the efficacy and reduce the toxicity of doxorubicin in other tissues and organs. Several intelligent PMs have already been in the clinical research stage and planned for market. Therefore, related research remains active, and the latest nanotechnology approaches for doxorubicin delivery are always in the spotlight. Centring on the model drugs doxorubicin, this review summarised the mechanisms of PMs, classified the polymers used in the application of doxorubicin delivery and discussed some interesting and imaginative smart PMs in recent years.

pH-Sensitive Mixed Micelles Assembled from PDEAEMA-PPEGMA and PCL-PPEGMA for Doxorubicin Delivery: Experimental and DPD Simulations Study

To decrease critical micelle concentration (CMC), improve stability, and keep high drug-loading capacity, three pH-sensitive mixed micelles applied for anticancer drug controlled delivery were prepared by the mixture of polymers poly (N,N-diethylaminoethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate) (PDEAEMA-PPEGMA) and polycaprolactone-b-poly (poly(ethylene glycol) methyl ether methacrylate) (PCL-PPEGMA), which were synthesized and confirmed by 1H NMR and gel permeation chromatographic (GPC). The critical micelle concentration (CMC) values of the prepared mixed micelles were low, and the micellar sizes and zeta potentials of the blank mixed micelles demonstrated good pH-responsive behavior. Combined experimental techniques with dissipative particle dynamics (DPD) simulation, the particle sizes, zeta potentials, drug loading content (LC), encapsulation efficiency (EE), aggregation morphologies, and doxorubicin (DOX) distribution of the mixed micelles were investigated, and the high DOX-loading capacity of the mixed micelles was found. Both in vitro DOX release profiles and DPD simulations of the DOX dynamics release process exhibited less leakage and good stability in neutral conditions and accelerated drug release behavior with a little initial burst in slightly acidic conditions. Cytotoxicity tests showed that the polymer PDEAEMA-PPEGMA and the blank mixed micelles had good biocompatibility, and DOX-loaded mixed micelles revealed certain cytotoxicity. These results suggest that the drug-loaded mixed micelles that consisted of the two polymers PDEAEMA-PPEGMA and PCL-PPEGMA can be new types of pH-responsive well-controlled release anticancer drug delivery mixed micelles.

Improvement of conventional anti-cancer drugs as new tools against multidrug resistant tumors

Multidrug resistance (MDR) is the dominant cause of the failure of cancer chemotherapy. The design of antitumor drugs that are able to evade MDR is rapidly evolving, showing that this area of biomedical research attracts great interest in the scientific community. The current review explores promising recent approaches that have been developed with the aim of circumventing or overcoming MDR. Encouraging results have been obtained in the investigation of the MDR-modulating properties of various classes of natural compounds and their analogues. Inhibition of P-gp or downregulation of its expression have proven to be the main mechanisms by which MDR can be surmounted. The use of hybrid molecules that are able to simultaneously interact with two or more cancer cell targets is currently being explored as a means to circumvent drug resistance. This strategy is based on the design of hybrid compounds that are obtained either by merging the structural features of separate drugs, or by conjugating two drugs or pharmacophores via cleavable/non-cleavable linkers. The approach is highly promising due to the pharmacokinetic and pharmacodynamic advantages that can be achieved over the independent administration of the two individual components. However, it should be stressed that the task of obtaining successful multivalent drugs is a very challenging one. The conjugation of anticancer agents with nitric oxide (NO) donors has recently been developed, creating a particular class of hybrid that can combat tumor drug resistance. Appropriate NO donors have been shown to reverse drug resistance via nitration of ABC transporters and by interfering with a number of metabolic enzymes and signaling pathways. In fact, hybrid compounds that are produced by covalently attaching NO-donors and antitumor drugs have been shown to elicit a synergistic cytotoxic effect in a variety of drug resistant cancer cell lines. Another strategy to circumvent MDR is based on nanocarrier-mediated transport and the controlled release of chemotherapeutic drugs and P-gp inhibitors. Their pharmacokinetics are governed by the nanoparticle or polymer carrier and make use of the enhanced permeation and retention (EPR) effect, which can increase selective delivery to cancer cells. These systems are usually internalized by cancer cells via endocytosis and accumulate in endosomes and lysosomes, thus preventing rapid efflux. Other modalities to combat MDR are described in this review, including the pharmaco-modulation of acridine, which is a well-known scaffold in the development of bioactive compounds, the use of natural compounds as means to reverse MDR, and the conjugation of anticancer drugs with carriers that target specific tumor-cell components. Finally, the outstanding potential of in silico structure-based methods as a means to evaluate the ability of antitumor drugs to interact with drug transporters is also highlighted in this review. Structure-based design methods, which utilize 3D structural data of proteins and their complexes with ligands, are the most effective of the in silico methods available, as they provide a prediction regarding the interaction between transport proteins and their substrates and inhibitors. The recently resolved X-ray structure of human P-gp can help predict the interaction sites of designed compounds, providing insight into their binding mode and directing possible rational modifications to prevent them from becoming P-gp drug substrates. In summary, although major efforts were invested in the search for new tools to combat drug resistant tumors, they all require further implementation and methodological development. Further investigation and progress in the abovementioned strategies will provide significant advances in the rational combat against cancer MDR.

Vinblastine-Loaded Nanoparticles with Enhanced Tumor-Targeting Efficiency and Decreasing Toxicity: Developed by One-Step Molecular Imprinting Process

Molecularly imprinted polymers have exhibited good performance as carriers on drug loading and sustained release. In this paper, vinblastine (VBL)-loaded polymeric nanoparticles (VBL-NPs) were prepared by a one-step molecular imprinting process, avoiding the waste and incomplete removal of the template, and evaluated as targeting carriers for VBL delivery after modification. Using acryloyl amino acid comonomers and disulfide cross-linkers, VBL-NPs were synthesized and then conjugated with poly(ethylene glycol)-folate. The dynamic size of the obtained VBL-NPs-PEG-FA was 258.3 nm (PDI = 0.250), and the encapsulation efficiency was 45.82 ± 1.45%. The nanoparticles of VBL-NPs-PEG-FA were able to completely release VBL during 48 h under a mimic tumor intracellular condition (pH 4.5, 10 mM glutathione (GSH)), displaying significant redox responsiveness, whereas the release rates were much slower in the mimic body liquid (pH 7.4, 2 μM GSH) and tumor extracellular environment (pH 6.5, 2 μM GSH). Furthermore, the carriers NPs-PEG-FA, prepared without VBL, showed satisfactory intrinsic hemocompatibility, cellular compatibility, and tumor-targeting properties: they could rapidly and efficiently accumulate to folate receptor positive Hela cells and then internalized via receptor-mediated endocytosis, and the retention in tumor tissues could last for over 48 h. Interestingly, VBL-NPs-PEG-FA could evidently increase the accumulation of VBL in tumor tissues while decreasing the distribution of VBL in organs, exert similar anticancer efficacy against Hela tumors in the xenograft model of nude mice to VBL injection, and significantly improve the abnormality of liver and spleen observed in VBL injection. VBL-NPs-PEG-FA has the potential to be the delivery carrier for VBL by enhancing the tumor-targeting efficacy of VBL and decreasing toxicity to normal tissues.

Zwitterionic pH-responsive hyaluronic acid polymer micelles for delivery of doxorubicin

As zwitterionic polymers show great promise in drug delivery, hyaluronic acid (HA) was deacetylated and grafted with dodecylamine to prepare a pH-sensitive zwitterionic polymer dHAD used as a carrier for antitumor drugs. The polymer was negatively charged at pH 7.4 and became positive at pH 6.2. In vitro delivery of DOX against MCF-7 cells showed that the blank micelle dHAD had low cytotoxicity and the dHAD-DOX micelles could greatly prohibit the growth of the MCF-7 cells. In addition, the dHAD-DOX micelles had higher cellular uptake, indicating that the micelles were rapidly internalized into the cells via CD44 receptor-mediated endocytosis. The in vivo delivery of DOX to tumor-bearing mice confirmed that the dHAD-DOX micelles greatly inhibited the tumor growth and significantly reduced systemic toxicity of DOX. These results demonstrated that biocompatible pH-responsive zwitterionic dHAD micelles are promising carriers for the delivery of DOX.

Multifunctional approaches utilizing polymeric micelles to circumvent multidrug resistant tumors

The concerns impeding the success of chemotherapy in cancer is descending efficacy of drugs due to the development of multiple drug resistance (MDR). The current efforts employed to overcome MDR have failed or are limited to only preliminary in-vitro investigations. Nanotechnology is at the forefront of the drug delivery research, playing pivotal role in chemotherapy and diagnosis, thereby providing innovative approaches for the management of the disease with minimal side effects. Recently, polymeric micelles (PMs) have witnessed significant developments in cancer therapy. PMs are self-assembled colloidal particles, with a hydrophilic head and a long hydrophobic tail, which enhance the solubility, permeability and bioavailability of drugs, due to the unique features of reaching higher concentration in the biological system, above critical micellar concentration. One of the effective approaches to improve the efficacy of chemotherapy and overcome drug resistance would be to employ multifunctional approach (combination of stimuli-responsive, utilization of drug resistance modulators and combination therapy) using PMs as drug delivery systems. Actively targeted, stimuli-sensitive and multifunctional approaches involve using single and/or combination of approaches (pH-responsive, temperature regulated, reduction-sensitive, ultrasound etc.) to combat drug resistant. The review will describe PMs, types of copolymers used in PMs, preparation and characterization of PMs. A comprehensive list of PMs tested in clinical trials is discussed. Lastly, this review covers stimuli-sensitive and multifunctional approaches to overcome MDR in cancer utilizing PMs.

Poly(Ethylene Glycol)-Polylactide Micelles for Cancer Therapy

For the treatment of malignancy, many therapeutic agents, including small molecules, photosensitizers, immunomodulators, proteins and genes, and so forth, have been loaded into nanocarriers for controllable cancer therapy. Among these nanocarriers, polymeric micelles have been considered as one of the most promising nanocarriers, some of which have already been applied in different stages of clinical trials. The successful advantages of polymeric micelles from bench to bedside are due to their special core/shell structures, which can carry specific drugs in certain disease conditions. Particularly, poly(ethylene glycol)–polylactide (PEG–PLA) micelles have been considered as one of the most promising platforms for drug delivery. The PEG shell effectively prevents the adsorption of proteins and phagocytes, thereby evidently extending the blood circulation period. Meanwhile, the hydrophobic PLA core can effectively encapsulate many therapeutic agents. This review summarizes recent advances in PEG–PLA micelles for the treatment of malignancy. In addition, future perspectives for the development of PEG–PLA micelles as drug delivery systems are also presented.

Smart Nanoparticles Undergo Phase Transition for Enhanced Cellular Uptake and Subsequent Intracellular Drug Release in a Tumor Microenvironment

Inefficient cellular uptake and intracellular drug release at the tumor site are two major obstacles limiting the antitumor efficacy of nanoparticle delivery systems. To overcome both problems, we designed a smart nanoparticle that undergoes phase transition in a tumor microenvironment (TME). The smart nanoparticle is generated using a lipid-polypetide hybrid nanoparticle, which comprises a PEGylated lipid monolayer shell and a pH-sensitive hydrophobic poly-l-histidine core and is loaded with the antitumor drug doxorubicin (DOX). The smart nanoparticle undergoes a two-step phase transition at two different pH values in the TME: (i) At the TME (pH_e: 7.0-6.5), the smart nanoparticle swells, and its surface potential turns from negative to neutral, facilitating the cellular uptake; (ii) After internalization, at the acid endolysosome (pH_endo: 6.5-4.5), the smart nanoparticle dissociates and induces endolysosome escape to release DOX into the cytoplasm. In addition, a tumor-penetrating peptide iNRG was modified on the surface of the smart nanoparticle as a tumor target moiety. The in vitro studies demonstrated that the iNGR-modified smart nanoparticles promoted cellular uptake in the acidic environment (pH 6.8). The in vivo studies showed that the iNGR-modified smart nanoparticles exerted more potent antitumor efficacy against late-stage aggressive breast carcinoma than free DOX. These data suggest that the smart nanoparticles may serve as a promising delivery system for sequential uptake and intracellular drug release of antitumor agents. The easy preparation of these smart nanoparticles may also have advantages in the future manufacture for clinical trials and clinical use.

pH-Responsive Nanoscale Coordination Polymer for Efficient Drug Delivery and Real-Time Release Monitoring

Both excess dosages of drug and unwanted drug carrier can lead to severe side effects as well as the failure of tumor therapy. Here, an Fe³⁺ -gallic acid based drug delivery system is designed for efficient monitoring of drug release in tumor. Fe³⁺ and polyphenol gallic acid can form polygonal nanoscale coordination polymer in aqueous solution, which exhibits certain antitumor effect. Importantly, this coordination polymer possesses extremely high doxorubicin (DOX) loading efficacy (up to 48.3%). In vitro studies demonstrate that the fluorescence of DOX can be quenched efficiently when DOX is loaded on the coordination polymer. The acidity in lysosome also triggers the release of DOX and fluorescence recovery simultaneously, which realizes real-time monitoring of drug release in tumor cells. In vivo studies further indicate that this polyphenol-rich drug delivery system can significantly inhibit tumor growth with negligible heart toxicity of DOX. This system with minimal side effects should be a promising nanoplatform for tumor treatment.

pH-sensitive and folic acid-targeted MPEG-PHIS/FA-PEG-VE mixed micelles for the delivery of PTX-VE and their antitumor activity

The aim of this study was to simultaneously introduce pH sensitivity and folic acid (FA) targeting into a micelle system to achieve quick drug release and to enhance its accumulation in tumor cells. Paclitaxel-(+)-α-tocopherol (PTX-VE)-loaded mixed micelles (PHIS/FA/PM) fabricated by poly(ethylene glycol) methyl ether-poly(histidine) (MPEG-PHIS) and folic acid-poly(ethylene glycol)-(+)-α-tocopherol (FA-PEG-VE) were characterized by dynamic light scattering and transmission electron microscopy (TEM). The mixed micelles had a spherical morphology with an average diameter of 137.0±6.70 nm and a zeta potential of -48.7±4.25 mV. The drug encapsulation and loading efficiencies were 91.06%±2.45% and 5.28%±0.30%, respectively. The pH sensitivity was confirmed by changes in particle size, critical micelle concentration, and transmittance as a function of pH. MTT assay showed that PHIS/FA/PM had higher cytotoxicity at pH 6.0 than at pH 7.4, and lower cytotoxicity in the presence of free FA. Confocal laser scanning microscope images demonstrated a time-dependent and FA-inhibited cellular uptake. In vivo imaging confirmed that the mixed micelles targeted accumulation at tumor sites and the tumor inhibition rate was 85.97%. The results proved that the mixed micelle system fabricated by MPEG-PHIS and FA-PEG-VE is a promising approach to improve antitumor efficacy.

Transferrin receptor-targeted pH-sensitive micellar system for diminution of drug resistance and targetable delivery in multidrug-resistant breast cancer

The emergence of drug resistance is partially associated with overproduction of transferrin receptor (TfR). To overcome multidrug resistance (MDR) and achieve tumor target delivery, we designed a novel biodegradable pH-sensitive micellar system modified with HAIYPRH, a TfR ligand (7pep). First, the polymers poly(l-histidine)-coupled polyethylene glycol-2000 (PHIS-PEG₂₀₀₀) and 7pep-modified 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-polyethylene glycol-2000 (7pep-DSPE-PEG₂₀₀₀) were synthesized, and the mixed micelles were prepared by blending of PHIS-PEG₂₀₀₀ and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-polyethylene glycol-2000 (DSPE-PEG₂₀₀₀) or 7pep-DSPE-PEG₂₀₀₀ (7-pep HD micelles). The micelles exhibited good size uniformity, high encapsulation efficiency, and a low critical micelle concentration. By changing the polymer ratio in the micellar formulation, the pH response range was specially tailored to pH ~6.0. When loaded with antitumor drug doxorubicin (DOX), the micelle showed an acid pH-triggering drug release profile. The cellular uptake and cytotoxicity study demonstrated that 7-pep HD micelles could significantly enhance the intracellular level and antitumor efficacy of DOX in multidrug-resistant cells (MCF-7/Adr), which attributed to the synergistic effect of poly(l-histidine)-triggered endolysosom escape and TfR-mediated endocytosis. Most importantly, the in vivo imaging study confirmed the target-ability of 7-pep HD micelles to MDR tumor. These findings indicated that 7-pep HD micelles would be a promising drug delivery system in the treatment of drug-resistant tumors.

Building the design, translation and development principles of polymeric nanomedicines using the case of clinically advanced poly(lactide(glycolide))-poly(ethylene glycol) nanotechnology as a model: An industrial viewpoint

The design of the first polymeric nanoparticles could be traced back to the 1970s, and has thereafter received considerable attention, as evidenced by the significant increase of the number of articles and patents in this area. This review article is an attempt to take advantage of the existing literature on the clinically tested and commercialized biodegradable PLA(G)A-PEG nanotechnology as a model to propose quality building and outline translation and development principles for polymeric nano-medicines. We built such an approach from various building blocks including material design, nano-assembly - i.e. physicochemistry of drug/nano-object association in the pharmaceutical process, and release in relevant biological environment - characterization and identification of the quality attributes related to the biopharmaceutical properties. More specifically, as envisaged in a translational approach, the reported data on PLA(G)A-PEG nanotechnology have been structured into packages to evidence the links between the structure, physicochemical properties, and the in vitro and in vivo performances of the nanoparticles. The integration of these bodies of knowledge to build the CMC (Chemistry Manufacturing and Controls) quality management strategy and finally support the translation to proof of concept in human, and anticipation of the industrialization takes into account the specific requirements and biopharmaceutical features attached to the administration route. From this approach, some gaps are identified for the industrial development of such nanotechnology-based products, and the expected improvements are discussed. The viewpoint provided in this article is expected to shed light on design, translation and pharmaceutical development to realize their full potential for future clinical applications.

Polylactic acid (PLA) controlled delivery carriers for biomedical applications

Polylactic acid (PLA) and its copolymers have a long history of safety in humans and an extensive range of applications. PLA is biocompatible, biodegradable by hydrolysis and enzymatic activity, has a large range of mechanical and physical properties that can be engineered appropriately to suit multiple applications, and has low immunogenicity. Formulations containing PLA have also been Food and Drug Administration (FDA)-approved for multiple applications making PLA suitable for expedited clinical translatability. These biomaterials can be fashioned into sutures, scaffolds, cell carriers, drug delivery systems, and a myriad of fabrications. PLA has been the focus of a multitude of preclinical and clinical testing. Three-dimensional printing has expanded the possibilities of biomedical engineering and has enabled the fabrication of a myriad of platforms for an extensive variety of applications. PLA has been widely used as temporary extracellular matrices in tissue engineering. At the other end of the spectrum, PLA's application as drug-loaded nanoparticle drug carriers, such as liposomes, polymeric nanoparticles, dendrimers, and micelles, can encapsulate otherwise toxic hydrophobic anti-tumor drugs and evade systemic toxicities. The clinical translation of these technologies from preclinical experimental settings is an ever-evolving field with incremental advancements. In this review, some of the biomedical applications of PLA and its copolymers are highlighted and briefly summarized.

A review of the ligands and related targeting strategies for active targeting of paclitaxel to tumours

It has been 30 years since the discovery of the anti-tumour property of paclitaxel (PTX), which has been successfully applied in clinic for the treatment of carcinomas of the lungs, breast and ovarian. However, PTX is poorly soluble in water and has no targeting and selectivity to tumour tissue. Recent advances in active tumour targeting of PTX delivery vehicles have addressed some of the issues related to lack of solubility in water and non-specific toxicities associated with PTX. These PTX delivery vehicles are designed for active targeting to specific cancer cells by the addition of ligands for recognition by specific receptors/antigens on cancer cells. This article will focus on various ligands and related targeting strategies serving as potential tools for active targeting of PTX to tumour tissues, illustrating their use in different tumour models. This review also highlights the need of further studies on the discovery of receptors in different cells of specific organ and ligands with binding efficiency to these specific receptors.

Preparation of pH and redox dual-sensitive core crosslinked micelles for overcoming drug resistance of DOX

When incubating the pH and redox dual-sensitive CCL/SS micelles with MCF-7/ADR cells, they could sufficiently overcome drug resistance to deliver DOX into MCF-7/ADR cells, leading to the apoptosis of tumor cells.

Novel folated Pluronic/poly(lactic acid) nanoparticles for targeted delivery of paclitaxel

In vivo prolonged circulation time and enhanced tumor resistant ability of targeted PTX-loaded FA–Pluronic–PLA nanoparticles.

Smart pH-responsive and high doxorubicin loading nanodiamond for in vivo selective targeting, imaging, and enhancement of anticancer therapy

We introduce a simple and effective strategy to design a promising drug delivery platform for improving the biomedical applications of smart nanodiamond carriers.

Recent advances in polymeric micelles for anti-cancer drug delivery

Block co-polymeric micelles receive increased attention due to their ability to load therapeutics, deliver the cargo to the site of action, improve the pharmacokinetic of the loaded drug and reduce off-target cytotoxicity. While polymeric micelles can be developed with improved drug loading capabilities by modulating hydrophobicity and hydrophilicity of the micelle forming block co-polymers, they can also be successfully cancer targeted by surface modifying with tumor-homing ligands. However, maintenance of the integrity of the self-assembled system in the circulation and disassembly for drug release at the site of drug action remain a challenge. Therefore, stimuli-responsive polymeric micelles for on demand drug delivery with minimal off-target effect has been developed and extensively investigated to assess their sensitivity. This review focuses on discussing various polymeric micelles currently utilized for the delivery of chemotherapeutic drugs. Designs of various stimuli-sensitive micelles that are able to control drug release in response to specific stimuli, either endogenous or exogenous have been delineated.

Folate-targeting redox hyperbranched poly(amido amine)s delivering MMP-9 siRNA for cancer therapy

For effective gene delivery to breast cancer MCF-7 cells, a folate-targeting redox gene carrier was synthesized by Michael addition polymerization between 1-(2-aminoethyl)piperazine and N,N'-cystaminebisacrylamide. Folate was then conjugated through an amidation reaction. The obtained folate-modified hyperbranched poly(amido amine)s (FA-PAAs) degraded in the presence of glutathione and displayed excellent transfection efficiency in vitro. In particular, FA-PAAs showed much higher gene delivery efficiency than PEI-25k in the presence of serum, leading to an obvious decrease in MMP-9 protein expression and the apoptosis of MCF-7 cells. Moreover, FA-PAAs displayed lower cytotoxicity and better blood compatibility than PEI-25k, suggesting a potential application in gene therapy for tumors.