Poly(ethyleneglycol)-b-Poly(ε-caprolactone-co-γ-hydroxyl-ε- caprolactone) Bearing Pendant Hydroxyl Groups as Nanocarriers for Doxorubicin Delivery

Advancements in nanoscale delivery systems: optimizing intermolecular interactions for superior drug encapsulation and precision release

Nanoscale preparations, such as nanoparticles, micelles, and liposomes, are increasingly recognized in pharmaceutical technology for their high capability in tailoring the pharmacokinetics of the encapsulated drug within the body. These preparations have great potential in extending drug half-life, reducing dosing frequency, mitigating drug side effects, and enhancing drug efficacy. Consequently, nanoscale preparations offer promising prospects for the treatment of metabolic disorders, malignant tumors, and various chronic diseases. Nevertheless, the complete clinical potential of nanoscale preparations remains untapped due to the challenges associated with low drug loading degrees and insufficient control over drug release. In this review, we comprehensively summarize the vital role of intermolecular interactions in enhancing encapsulation and controlling drug release within nanoscale delivery systems. Our analysis critically evaluates the characteristics of common intermolecular interactions and elucidates the techniques employed to assess them. Moreover, we highlight the significant potential of intermolecular interactions in clinical translation, particularly in the screening and optimization of preparation prescriptions. By attaining a deeper understanding of intermolecular interaction properties and mechanisms, we can adopt a more rational approach to designing drug carriers, leading to substantial advancements in the application and clinical transformation of nanoscale preparations. Moving forward, continued research in this field offers exciting prospects for unlocking the full clinical potential of nanoscale preparations and revolutionizing the field of drug delivery.

A new nano hyperbranched β-pinene polymer: Controlled synthesis and nonviral gene delivery

Recently, an extensive research effort has been directed toward the improvement of nonviral transfection vectors, such as polymeric materials. The macromolecular structure of polymers has a substantial effect on their transfection efficacy. In this context, the modern advances in polymer production techniques, such as the deactivation-enhanced radical atom transfer polymerization (DE-ATRP), have been fundamental for the synthesis of controlled architecture nanomaterials. In this study, hyperbranched poly(β-pinene)-PDMAEMA-PEGDMA nanometric copolymers were synthesised at high conversion via DE-ATRP using different concentrations of β-pinene for gene delivery applications. The structural characterization and the biological performance of the materials were investigated. The copolymers' molar mass (10,434-16,438 mol l^-1), dispersity, and conversion (90-95%) varied significantly with β-pinene proportion on the polymerizations. The polymer-gene complexes generated (280-110 nm) presented excellent solution stability due to the β-pinene segment on the copolymers. Gene delivery and transfection were highly dependent on the copolymer composition. The copolymers containing the highest β-pinene proportions exhibited the best results with high transfection effectivity. In conclusion, the incorporation of β-pinene in DMAEMA-PEGMA copolymer formulations is a renewable option to improve the materials' branching ratio, polyplex stability, and gene delivery performance without causing cytotoxic effects.

Multicompartment Nanoparticles by Crystallization-Driven Self-Assembly of Star Polymers: Combining High Stability and Loading Capacity

Herein novel multicompartment nanoparticles (MCNs) that combine high stability and cargo loading capacity are developed. The MCNs are fabricated by crystallization-driven self-assembly (CDSA) of a tailor-made 21 arm star polymer, poly(L-lactide)[poly(tert-butyl acrylate)-block-poly(ethylene glycol)]₂₀ [PLLA(PtBA-b-PEG)₂₀ ]. Platelet-like or spherical MCNs containing a crystalline PLLA core and hydrophobic PtBA subdomains are formed and stabilized by PEG. Hydrophobic cargos, such as Nile Red and chemotherapeutic drug doxorubicin, can be successfully encapsulated into the collapsed PtBA subdomains with loading capacity two orders of magnitude higher than traditional CDSA nanoparticles. Depolarized fluorescence measurements of the Nile Red loaded MCNs suggest that the free volume of the hydrophobic chains in the nanoparticles may be the key for regulating their drug loading capacity. In vitro study of the MCNs suggests excellent cytocompatibility of the blank nanoparticles as well as a dose-dependent cellular uptake and cytotoxicity of the drug-loaded MCNs.

Folic Acid-Decorated β-Cyclodextrin-Based Poly(ε-caprolactone)-dextran Star Polymer with Disulfide Bond-Linker as Theranostic Nanoparticle for Tumor-Targeted MRI and Chemotherapy

β-cyclodextrin(βCD)-based star polymers have attracted much interest because of their unique structures and potential biomedical and biological applications. Herein, a well-defined folic acid (FA)-conjugated and disulfide bond-linked star polymer ((FA-Dex-SS)-βCD-(PCL)₁₄) was synthesized via a couple reaction between βCD-based 14 arms poly(ε-caprolactone) (βCD-(PCL)₁₄) and disulfide-containing α-alkyne dextran (alkyne-SS-Dex), and acted as theranostic nanoparticles for tumor-targeted MRI and chemotherapy. Theranostic nanoparticles were obtained by loading doxorubicin (DOX), and superparamagnetic iron oxide (SPIO) particles were loaded into the star polymer nanoparticles to obtain ((FA-Dex-SS)-βCD-(PCL)₁₄@DOX-SPIO) theranostic nanoparticles. In vitro drug release studies showed that approximately 100% of the DOX was released from disulfide bond-linked theranostic nanoparticles within 24 h under a reducing environment in the presence of 10.0 mM GSH. DOX and SPIO could be delivered into HepG2 cells efficiently, owing to the folate receptor-mediated endocytosis process of the nanoparticles and glutathione (GSH), which triggered disulfide-bonds cleaving. Moreover, (FA-Dex-SS)-βCD-(PCL)₁₄@DOX-SPIO showed strong MRI contrast enhancement properties. In conclusion, folic acid-decorated reduction-sensitive star polymeric nanoparticles are a potential theranostic nanoparticle candidate for tumor-targeted MRI and chemotherapy.

Multifunctional polymeric micellar nanomedicine in the diagnosis and treatment of cancer

Polymeric micelles are a prevalent topic of research for the past decade, especially concerning their fitting ability to deliver drug and diagnostic agents. This delivery system offers outstanding advantages, such as biocompatibility, high loading efficiency, water-solubility, and good stability in biological fluids, to name a few. The multifunctional polymeric micellar architect offers the added capability to adapt its surface to meet the looked-for clinical needs. This review cross-talks the recent reports, proof-of-concept studies, patents, and clinical trials that utilize polymeric micellar family architectures concerning cancer targeted delivery of anticancer drugs, gene therapeutics, and diagnostic agents. The manuscript also expounds on the underlying opportunities, allied challenges, and ways to resolve their bench-to-bedside translation for allied clinical applications.

Development and Optimization of Irinotecan-Loaded PCL Nanoparticles and Their Cytotoxicity against Primary High-Grade Glioma Cells

BACKGROUND

High-grade gliomas (HGGs) are highly malignant tumors with a poor survival rate. The inability of free drugs to cross the blood-brain barrier and their off-target accumulation result in dose-limiting side effects. This study aimed at enhancing the encapsulation efficiency (EE) of irinotecan hydrochloride trihydrate (IRH) within polycaprolactone (PCL) nanoparticles with optimized size and charge.

MATERIALS AND METHODS

IRH-loaded PCL nanoparticles were formulated using either the single emulsion (O/W, W/O and O/O) or double emulsion (W/O/O and W/O/W) solvent evaporation techniques. The nanoparticles were characterized for their size, zeta potential and EE, with the optimized nanoparticles being characterized for their drug release and cytotoxicity.

RESULTS

The amorphization of PCL and the addition of electrolytes to the aqueous phases of the W/O/W emulsion produced spherical nanoparticles with a mean diameter of 202.1 ± 2.0 nm and an EE of 65.0%. The IRH-loaded nanoparticles exhibited zero-order release and were cytotoxic against primary HGG cells.

CONCLUSION

The amorphization of PCL improves its EE of hydrophilic drugs, while the addition of electrolytes to the aqueous phases of the W/O/W emulsion enhances their EE further. IRH-loaded PCL nanoparticles have the potential to deliver cytotoxic levels of IRH over a sustained period of time, enhancing the cell death of HGGs.

Formation of Uni-Lamellar Vesicles in Mixtures of DPPC with PEO-b-PCL Amphiphilic Diblock Copolymers

The ability of mixtures of 1.2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and the amphiphilic diblock copolymers poly (ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) to stabilize uni-lamellar nano-vesicles is reported. Small angle neutron scattering (SANS) is used to define their size distribution and bilayer structure and resolve the copresence of aggregates and clusters in solution. The vesicles have a broad size distribution which is compatible with bilayer membranes of relatively low bending stiffness. Their mean diameter increases moderately with temperature and their number density and mass is higher in the case of the diblock copolymer with the larger hydrophobic block. Bayesian analysis is performed in order to justify the use of the particular SANS fitting model and confirm the reliability of the extracted parameters. This study shows that amphiphilic block copolymers can be effectively used to prepare mixed lipid-block copolymer vesicles with controlled lamellarity and a significant potential as nanocarriers for drug delivery.

Theranostic Nanoparticles with Aggregation-Induced Emission and MRI Contrast Enhancement Characteristics as a Dual-Modal Imaging Platform for Image-Guided Tumor Photodynamic Therapy

Introduction

Advanced tumor-targeted theranostic nanoparticles play a key role in tumor diagnosis and treatment research. In this study, we developed a multifunctional theranostic platform based on an amphiphilic hyaluronan/poly-(N-ε-carbobenzyloxy-L-lysine) derivative (HA-g-PZLL), superparamagnetic iron oxide (SPIO) and aggregation-induced emission (AIE) nanoparticles for tumor-targeted magnetic resonance (MR) and fluorescence (FL) dual-modal image-guided photodynamic therapy (PDT).

Materials and Methods

The amphiphilic hyaluronan acid (HA) derivative HA-g-PZLL was synthesized by grafting hydrophobic poly-(N-ε-carbobenzyloxy-L-lysine) (PZLL) blocks onto hyaluronic acid by a click conjugation reaction. The obtained HA-g-PZLLs self-assembled into nanoparticles in the presence of AIE molecules and SPIO nanoparticles to produce tumor-targeted theranostic nanoparticles (SPIO/AIE@HA-g-PZLLs) with MR/FL dual-modal imaging ability. Cellular uptake of the theranostic nanoparticles was traced by confocal laser scanning microscopy (CLSM), flow cytometry and Prussian blue staining. The intracellular reactive oxygen species (ROS) generation characteristics of the theranostic nanoparticles were evaluated with CLSM and flow cytometry. The effect of PDT was evaluated by cytotoxicity assay. The dual-mode imaging ability of the nanoparticles was evaluated by a real-time near-infrared fluorescence imaging system and magnetic resonance imaging scanning.

Results

The resulting theranostic nanoparticles not only emit red fluorescence for high-quality intracellular tracing but also effectively produce singlet oxygen for photodynamic tumor therapy. In vitro cytotoxicity experiments showed that these theranostic nanoparticles can be efficiently taken up and are mainly present in the cytoplasm of HepG2 cells. After internalization, these theranostic nanoparticles showed serious cytotoxicity to the growth of HepG2 cells after white light irradiation.

Discussion

This work provides a simple method for the preparation of theranostic nanoparticles with AIE characteristics and MR contrast enhancement, and serves as a dual-modal imaging platform for image-guided tumor PDT.

Redox-responsive nanoparticles from disulfide bond-linked poly-(N-ε-carbobenzyloxy-l-lysine)-grafted hyaluronan copolymers as theranostic nanoparticles for tumor-targeted MRI and chemotherapy

Redox-responsive theranostic nanoparticles based on poly-(N-ε-carbobenzyloxy-l-lysine) (PZLL) grafted hyaluronan (HA) (HA-g-SS-PZLL) copolymers were constructed for hepatocellular carcinoma diagnosis and therapy. These hyaluronan derivatives formed nanoparticles via a self-assembly process in aqueous solution at low concentration. Theranostic nanoparticles were obtained after loading hydrophobic doxorubicin (DOX) and superparamagnetic iron oxide (SPIO) into the core of the nanoparticles via a dialysis method. Theranostic nanoparticles exhibited redox triggered DOX release behavior, and faster DOX released from theranostic nanoparticles was detected under a reducing environment compared with slow DOX release under a normal physiological environment. Confocal laser scanning microscopy (CLSM), flow cytometry and Prussian blue staining against HepG2 cells demonstrated that HA-g-SS-PZLL theranostic nanoparticles were capable of delivering DOX and SPIO into the cells. The analysis of the anticancer effect revealed that the HA-g-SS-PZLL theranostic nanoparticles shown higher cytotoxicity against HepG2 cells than DOX-loaded HA-g-PZLL nanoparticles. In vitro T₂ magnetic resonance imaging (MRI) results exhibited that theranostic nanoparticles showed a good contrast enhancement effect, and the r₂ relaxivity value was approximately 231 Fe mM^-1 s^-1. Finally, the theranostic nanoparticles acted as nanoprobes for HepG2 tumor-bearing BALB/c mice for in vivo MRI. Therefore, HA-g-SS-PZLL copolymers have great potential as theranostic nanoparticles for tumor-targeted diagnosis and treatment.

Synthesis of Thermo-Responsive Block-Graft Copolymer Based on PCL and PEG Analogs, and Preparation of Hydrogel via Click Chemistry

Thermo-responsive cross-linkable mPEG-b-[PCL-g-(MEO2MA-co-OEGMA)]-b-mPEG was synthesized by ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Then, the cross-linkable block-graft copolymer was used to prepare hydrogel via a copper-catalyzed 1,3-dipolar azide-alkyne cycloaddition reaction. The chemical structure and composition of copolymer were characterized by proton nuclear magnetic resonance (1H NMR), Fourier-transform infrared (FT-IR) and gel permeation chromatography (GPC). The self-assembly behaviors of the copolymer in aqueous solution were studied by UV spectrophotometer, fluorescence probes, the surface tension method, dynamic light scattering, and transmission electron microscopy. The results proved that the copolymer has excellent solubility and better temperature response. The three-dimensional network structure of the gels, observed by scanning electron microscopy at different temperatures, indicated that the gels have temperature response.

Magnetic particle ornamented dual stimuli responsive nanogel for controlled anticancer drug delivery

A series of spherical magneto-responsive nanogels were fabricated by formulating different sets of star block copolymers based on pentaerythritol–poly(ε-caprolactone)-b-poly(acrylic acid) (PE–PCL-b-PAA) combined with amine-functionalized magnetic nanoparticles for targeted cancer therapy.

Reduction sensitive hyaluronan-SS-poly(ε-caprolactone) block copolymers as theranostic nanocarriers for tumor diagnosis and treatment

Tumor-targeted multifunctional nanocarriers play an important role in tumor diagnosis and treatment. Herein, disulfide bonds linked amphiphilic hyaluronan-SS-poly(ε-caprolactone) diblock copolymers (HA-SS-PCL) were synthesized and studied as theranostic nanocarriers for tumor diagnosis and treatment. The chemical structure of HA-SS-PCL was confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (¹H NMR). The self-assembling behavior of the HA-SS-PCL into GSH-responsive micelles and their degradation were characterized by fluorescence spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). Theranostic nanocarriers encapsulating doxorubicin (DOX) and superparamagnetic iron oxide (SPIO) were formed via a dialysis. In vitro drug release results suggested that the HA-SS-PCL micelles possessed reductant-triggered doxorubicin release ability, which was confirmed by 100% of DOX release from HA-SS-PCL micelles within 12 h under 10 mM of glutathione (GSH), whereas about 40% of DOX was released under non-reductive condition within 24 h. Both flow cytometry and confocal laser scanning microscopy (CLSM) analysis revealed that the HA-SS-PCL micelles loaded with DOX were internalized in HepG2 cell via a receptor mediated mechanism between hyaluronan and the CD44 receptor. Furthermore, the MTT assay and cell apoptosis analysis revealed that the DOX-loaded HA-SS-PCL micelles exhibited pronounced antitumor ability towards HepG2 cells compared with that of the reduction-insensitive HA-PCL micelles at the same DOX dosage. The r₂ relaxivity value of the DOX/SPIO loaded HA-SS-PCL micelles was up to 221.2 mM^-1 s^-1 (Fe). Thus, the obtained HA-SS-PCL block copolymers demonstrate promising potential as tumor targeting theranostic nanocarriers in the field of tumor diagnosis and treatment.

Preparation and evaluation of highly biocompatible nanogels with pH-sensitive charge-convertible capability based on doxorubicin prodrug

In this paper, to achieve the targeted ability of anti-tumor drug doxorubicin (DOX), enhance the treatment effect and reduce the side effect, a novel pH-sensitive and charge-convertible prodrug nanogel was prepared. Firstly, cis-aconitic anhydride-doxorubicin prodrug (CAD) and Pluronic F127-chitosan-CAD (F127-CS-CAD) conjugates were synthesized. Then the DOX loaded polyion complex micelles (F127-CS-CAD/CAD) were prepared by self-assembling, thus CAD was incorporated into micelles via electrostatic interactions between electronegative CAD and positively charged F127-CS-CAD and hydrophobic interactions. Finally a pH-responsive charge-convertible copolymer, folic acid modified gelatin (Gel-FA) was shielded on the surface of micelles and the Gel-FA/F127-CS-CAD/CAD nanogel was formed, the charge-convertible capability was evaluated through changes of the morphology and Zeta potential under different pH value environment by transmission electron microscopy (TEM) and Zeta potential analyzer. And in vitro pH-dependent and two-phase drug release from nanogel was also evaluated. In vitro anti-tumor activity of Gel-FA/F127-CS-CAD/CAD nanogel was performed on HeLa cells and HepG2 cells to prove the strong cell toxicity of nanogels. Finally, the in vivo safety experiments showed that the nanogel achieved the reducing the toxic side effects of DOX significantly.

Pyrene-Terminated, Amphiphilic Polypeptide and Its Hydrogen-Bonded Interpolymer Complex as Delivery Systems of Doxorubicin

The intensity ratio between the first (373 nm) and the third (383 nm) vibronic peaks [I ₁/I ₃, as the pyrene (Py) scale] of fluorescent Py was used to monitor the critical concentration, drug-loading, and -releasing behaviors of a Py-terminated, amphiphilic polypeptide PPM and its hydrogen-bonded interpolymer complex (HIPC) with poly(acrylic acid) (PAA). Primarily, an amphiphilic PPM with a hydrophobic Py terminal and hydrophilic methoxy-bis(ethylene oxide) pendant groups was synthesized through multiple preparative steps, and the resultant PPM was thoroughly mixed with PAA through a preferable hydrogen bond (H bond) interaction to form HIPC. The emission study suggested that the I ₁/I ₃ ratio and the quantum yield (Φ_F) are effective in determining the critical concentrations of the aqueous PPM and PPM/PAA solutions. Moreover, the I ₁/I ₃ ratio and Φ_F were found to be convenient measures for determining the amounts of doxorubicin drugs loaded by and released from the aqueous PPM and PPM/PAA solutions.

One-Step Preparation of pH-Responsive Polymeric Nanogels as Intelligent Drug Delivery Systems for Tumor Therapy

In this work, pH-responsive polypeptide-based nanogels are reported as potential drug delivery systems. By the formation of pH-sensitive benzoic imine bonds, pH-responsive nanogels are constructed using hydrophilic methoxy poly(ethylene glycol)- b-poly[ N-[ N-(2-aminoethyl)-2-aminoethyl]-l-glutamate] (MPEG- b-PNLG) and hydrophobic terephthalaldehyde (TPA) as a cross-linker. At pH 7.4, MPEG- b-PNLG nanogels exhibit high stabilities with hydrophobic inner cores, which allow encapsulation of hydrophobic therapeutic agents. Under tumoral acidic environments (pH ∼6.4), the cleavage of benzoic imine bonds induces the destruction of MPEG- b-PNLG nanogels and leads to rapid release of their payloads. The formation and pH sensitivity of the nanogels are investigated by dynamic light scattering. These nanogels exhibit excellent stabilities in the presence of salt or against dilution. The globular morphologies of the nanogels are confirmed using transmission electron microscopy. Doxorubicin is used as a model drug to evaluate drug encapsulation and release. Finally, the anticancer activities of the drug-encapsulated nanogels are assessed in vitro.

Synthesis of a ROS-responsive analogue of poly(ε-caprolactone) by the living ring-opening polymerization of 1,4-oxathiepan-7-one

A well-defined ROS-responsive block amphiphilic diblock copolymer PEO-b-POTO was synthesized to elucidate the oxidative degradation mechanism in assemblies.

Lignin-graft-Polyoxazoline Conjugated Triazole a Novel Anti-Infective Ointment to Control Persistent Inflammation

Lignin, one of the most abundant renewable feedstock, is used to develop a biocompatible hydrogel as anti-infective ointment. A hydrophilic polyoxazoline chain is grafted through ring opening polymerization, possess homogeneous spherical nanoparticles of 10-15 nm. The copolymer was covalently modified with triazole moiety to fortify the antimicrobial and antibiofilm activities. The hydrogel was capable of down regulating the expression level of IL-1β in LPS induced macrophage cells, and to cause significant reduction of iNOS production. It supported cellular anti-inflammatory activity which was confirmed with luciferase assay, western blot, and NF-κB analysis. This novel lignin-based hydrogel tested in-vivo has shown the abilities to prevent infection of burn wound, aid healing, and an anti-inflammatory dressing material. The hydrogel reported here provides a new material platform to introduce a cost-effective and efficient ointment option after undertaking further work to look at its use in the area of clinical practice.

Magnetite nanocluster and paclitaxel-loaded charge-switchable nanohybrids for MR imaging and chemotherapy

A charge-switchable nanohybrid system that triggered by the low pH value of tumor microenvironment has been created for enhancing MR imaging sensitivity and chemotherapy efficiency.

Biodegradable Copolymer for Stimuli-Responsive Sustained Release of Doxorubicin

Pendent functionalization of biodegradable polymers provides unique importance in biological applications. In this work, we have synthesized a polymeric nanocarrier for the controlled release of the anticancer drug doxorubicin (DOXI). Inspired by the pH responsiveness of acylhydrazine bonds along with the interesting self-assembly behavior of amphiphilic copolymers, this report delineates the development of a PEG-SS-PCL-DOXI copolymer consisting of DOXI, PEG, and a caprolactone backbone. First, the inclusion of a PEG moiety in the copolymer helps to achieve biocompatibility and aqueous solubility as well as a prolonged circulation time of the nanocarrier. Second, an acid-sensitive acylhydrazine-based linkage is chosen to attach DOXI to trigger sustained drug release, whereas the inclusion of an enzymatically cleavable disulfide linkage in the backbone adds to the advantage of backbone biodegradability at the intracellular level.

Tailor-Made Temperature-Sensitive Micelle for Targeted and On-Demand Release of Anticancer Drugs

The design of nanomedicines from the tuned architecture polymer is a leading object of immense research in recent years. Here, smart thermoresponsive micelles were prepared from novel architecture four-arm star block copolymers, namely, pentaerythritol polycaprolactone-b-poly(N-isopropylacrylamide) and pentaerythritol polycaprolactone-b-poly(N-vinylcaprolactam). The polymers were synthesized and tagged with folic acid (FA) to render them as efficient cancer cell targeting cargos. FA-conjugated block copolymers were self-assembled to a nearly spherical (ranging from 15 to 170 nm) polymeric micelle (FA-PM) with a sufficiently lower range of critical micelle concentration (0.59 × 10(-2) to 1.52 × 10(-2) mg/mL) suitable for performing as an efficient drug carrier. The blocks show lower critical solution temperature (LCST) ranging from 30 to 39 °C with high DOX-loading content (24.3%, w/w) as compared to that reported for a linear polymer in the contemporary literature. The temperature-induced reduction in size (57%) of the FA-PM enables a high rate of DOX release (78.57% after 24 h) at a temperature above LCST. The DOX release rate has also been tuned by on-demand administration of temperature. The in vitro biocompatibilities of the blank and DOX-loaded FA-PMs have been studied by the MTT assay. The cellular uptake study proves selective internalization of the FA-PM into cancerous cells (C6 glioma) compared that into normal cells (HaCaT). In vivo administration of the DOX-loaded FA-PMs into the C6 glioma rat tumor model resulted in significant accumulation in tumor sites, which drastically inhibited the tumor volume by ∼83.9% with respect to control without any significant systemic toxicity.

PEG based anti-cancer drug conjugated prodrug micelles for the delivery of anti-cancer agents

Development of polymer prodrug conjugates has evolved recently in the nano-medicine field for cancer diagnosis and treatment. This review focuses on the development of different types of PEG based polymer drug conjugates used for the delivery of anti-cancer agents.

Temperature-responsive in situ nanoparticle hydrogels based on hydrophilic pendant cyclic ether modified PEG-PCL-PEG

Thermo-sensitive injectable hydrogels based on poly(ε-caprolactone)/poly(ethylene glycol) (PCL/PEG) block copolymers have attracted considerable attention for sustained drug release and tissue engineering applications.

Self-assembly of well-defined triblock copolymers based on poly(lactic acid) and poly(oligo(ethylene glycol) methyl ether methacrylate) prepared by ATRP

Self-assembly of a series of amphiphilic poly(oligo(ethylene glycol) methyl ether methacrylate)-block-poly(lactic acid)-block-poly(oligo(ethylene glycol) methyl ether methacrylate) (P(OEGMA)-b-PLLA-b-P(OEGMA)) copolymers was investigated.

Prodrug Micelles Based on Norbornene-Functional Poly(lactide)s Backbone for Redox-Responsive Release of Paclitaxel

Norbornene-functional poly(lactide)s backbone-based amphiphilic copolymer, P(LA-g-mOEG)-b-P(LA-SS-COOH), was synthesized as the polymeric scaffold and paclitaxel (PTX) was directly conjugated to the carboxyl groups of the amphiphilic copolymer to obtain redox-responsive P(LA-g-mOEG)-b-P(LA-SS-PTX) prodrugs. The dynamic light scattering and transmission electron microscopy analyses showed that P(LA-g-mOEG)-b-P(LA-SS-PTX) self-assembled into prodrug micelles with a diameter of 60–70 nm and a low polydispersity in aqueous solution. Remarkably, in vitro release studies revealed that 80 % of PTX was released in 72 h under a reductive environment, whereas only 23 % of PTX was released in 72 h under non-reductive conditions. In addition, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays showed that P(LA-g-mOEG)-b-P(LA-SS-PTX) prodrug micelles retained high anti-tumour activity while polymer carriers were non-toxic up to a tested concentration of 1.0 mg mL–1. These redox-responsive prodrug micelles have tremendous potential for anti-tumour drug delivery.

A Smart Magnetically Active Nanovehicle for on-Demand Targeted Drug Delivery: Where van der Waals Force Balances the Magnetic Interaction

The magnetic field is a promising external stimulus for controlled and targeted delivery of therapeutic agents. Here, we focused on the preparation of a novel magnetically active polymeric micelle (MAPM) for magnetically targeted controlled drug delivery. To accomplish this, a number of superparamagnetic as well as biocompatible hybrid micelles were prepared by grafting four armed pentaerythretol poly(ε-caprolactone) (PE-PCL) onto the surface of Fe3O4 magnetic nanoparticles (MNPs) of two different ranges of size (∼5 nm and ∼15 nm). PE-PCL (four-armed) was synthesized by ring-opening polymerization, and it has been subsequently grafted onto the surface of modified MNP through urethane (-NHCO-) linkage. Polymer-immobilized MNP (5 and 15 nm) showed peculiar dispersion behavior. One displayed uniform dispersion of MNP (5 nm), while the other (15 nm) revealed associated structure. This type of size dependent contradictory dispersion behavior was realized by taking the van der Waals force as well as magnetic dipole-dipole force into consideration. The uniformly dispersed polymer immobilized MNP (5 nm) was used for the preparation of MAPM. The hydrodynamic size and bulk morphology of MAPM were studied by dynamic light scattering and high-resolution transmission electron microscopy. The anticancer drug (DOX) was encapsulated into the MAPM. The magnetic field triggers cell uptake of MAPM micelles preferentially toward targeted cells compare to untargeted ones. The cell viabilities of MAMP, DOX-encapsulated MAPM, and free DOX were studied against HeLa cell by MTT assay. In vitro release profile displayed about 51.5% release of DOX from MAPM (just after 1 h) under the influence of high frequency alternating magnetic field (HFAMF; prepared in-house device). The DOX release rate has also been tailored by on-demand application of HFAMF.

Amphiphilic polyelectrolyte/prodrug nanoparticles constructed by synergetic electrostatic and hydrophobic interactions with cooperative pH-sensitivity for controlled doxorubicin delivery

To achieve higher therapeutic efficiency with catabatic side effects, desirable nanocarriers should be designed to retain the loaded drug tightly during the systemic circulation, but release the drug rapidly and efficiently upon endocytosis by tumor cells. Herein, to achieve "off-on" controlled delivery of DOX, novel amphiphilic polyelectrolyte/prodrug nanoparticles (NPs) with cooperative pH-sensitivity were constructed via synergistic electrostatic and hydrophobic interactions between slightly positively charged methoxy polyethylene glycol-b-(poly(2-(diisopropylamino) ethyl methacrylate-co-aminopropyl methacrylamide) (PEDPA) copolymer and negatively charged cis-aconityl-doxorubicin (CAD) prodrug (termed as PEDPA/CAD NPs). With polymer-prodrug synergistic noncovalent interactions, the drug loading content of PEDPA/CAD NPs could be improved up to 12.6% with favorable serum stability, and significantly lowered the drug leakage to 2.5% within 24 h at pH 7.4. However, nearly 80% of encapsulated drug could be released at pH 5.0 within 12 h, due to the cooperative effects of the protonation of PDPA blocks resulting in quick disassembly of NPs and the rapid hydrolysis of cis-aconityl linkage leading to charge-reverse of CAD. Moreover, the results of fluorescent microscopy imaging and flow cytometry measurements exhibited that DOX could be recovered and released rapidly from PEDPA/CAD NPs upon endocytosis and then exert therapeutic action in the cell nucleus. Importantly, the PEDPA/CAD NPs exhibited significantly higher antitumor efficiency in vivo with reduced nonspecific toxicity to normal tissues in comparation with free DOX. In summary, the NPs designed in this work, constructed by synergistic electrostatic and hydrophobic interactions with cooperative pH-sensitivity, which potentially resolved the dilemma between systemic stability and rapid intracellular drug release, would provide a promising nanomedicine platform for cancer therapy.

Integrin-targeted pH-responsive micelles for enhanced efficiency of anticancer treatment in vitro and in vivo

The key to developing more nanocarriers for the delivery of drugs in clinical applications is to consider the route of the carrier from the administration site to the target tissue and to look for a simple design to complete this whole journey. We synthesized the amphiphilic copolymer cRGDfK-poly(ethylene glycol)-b-poly(2,4,6-trimethoxybenzylidene-1,1,1-tris(hydroxymethyl) ethane methacrylate) (cRGD-PETM) to construct multifunctional micelles. These micelles combined enhanced drug-loading efficiency with tumor-targeting properties, visual detection and controllable intracellular drug release, resulting in an improved chemotherapeutic effect in vivo. Doxorubicin (DOX) was encapsulated within the cRGD-PETM micelles as a model drug (termed as cRGD-PETM/DOX Ms). The size and morphology of the micelles were characterized systematically. As a result of the hydrophobic interaction and the π-π conjugation between the DOX molecules and the PTTMA copolymers, the cRGD-PETM/DOX Ms showed an excellent drug-loading capacity. The results of in vitro drug-release studies indicated that the cumulative release of DOX from cRGD-PETM/DOX Ms at pH 5.0 was twice that at pH 7.4. The results of fluorescent microscopic analysis showed that the cRGD-PETM/DOX Ms could be internalized by 4T1 and HepG2 cells via receptor-mediated endocytosis with rapid intracellular drug release, which resulted in increased cytotoxicity compared with free DOX. Ex vivo imaging studies showed that the cRGD-PETM/DOX Ms improved the accumulation and retention of the drug in tumor tissues. Studies of the in vivo anticancer effects showed that the cRGD-PETM/DOX Ms had a significantly higher therapeutic efficacy with lower side-effects than free DOX and PETM/DOX Ms. These results show that the multifunctional cRGD-PETM/DOX Ms have great potential as vehicles for the delivery of hydrophobic anticancer drugs.

Polymeric micelles with stimuli-triggering systems for advanced cancer drug targeting

Since the 1990s, nanoscale drug carriers have played a pivotal role in cancer chemotherapy, acting through passive drug delivery mechanisms and subsequent pharmaceutical action at tumor tissues with reduction of adverse effects. Polymeric micelles, as supramolecular assemblies of amphiphilic polymers, have been considerably developed as promising drug carrier candidates, and a number of clinical studies of anticancer drug-loaded polymeric micelle carriers for cancer chemotherapy applications are now in progress. However, these systems still face several issues; at present, the simultaneous control of target-selective delivery and release of incorporated drugs remains difficult. To resolve these points, the introduction of stimuli-responsive mechanisms to drug carrier systems is believed to be a promising approach to provide better solutions for future tumor drug targeting strategies. As possible trigger signals, biological acidic pH, light, heating/cooling and ultrasound actively play significant roles in signal-triggering drug release and carrier interaction with target cells. This review article summarizes several molecular designs for stimuli-responsive polymeric micelles in response to variation of pH, light and temperature and discusses their potentials as next-generation tumor drug targeting systems.

Effects of hydrophobic core components in amphiphilic PDMAEMA nanoparticles on siRNA delivery

Due to their biodegradable character, polyesters such as polycaprolactone (PCL), poly(D,L-lactide) (PDLLA), and polylactic-co-glycolic acid (PLGA) were widely used as the hydrophobic cores of amphiphilic cationic nanoparticles (NPs) for siRNA delivery. However, fewer researches focused on facilitating siRNA delivery by adjusting the polyester composition of these nanoparticles. Herein, we investigated the contribution of polyester segments in siRNA delivery in vitro by introducing different ratio of DLLA moieties in PCL segments of mPEG-block-PCL-graft-poly(dimethylamino ethyl methacrylate)(PEG-b-PCL-g-PDMAEMA). It was noticed that compared with the other ratios of DLLA moieties, a certain molar ratio (about 70%) of the NPs, named mPEG45-P(CL21-co-DLLA48)-g-(PDMAEMA29)2 (PECLD-70), showed the highest gene knockdown efficiency but poorest cellular uptake ability in vitro. Further research revealed that NPs with various compositions of the polyester cores showed different physicochemical properties including particle size, zeta potential and stiffness, leading to different endocytosis mechanisms thus influencing the cellular uptake efficiency. Subsequently, we observed that the cells treated by PECLD-70 NPs/Cy5 siRNA complexes exhibited more diffuse Cy5 signal distribution than other NPs by confocal laser scanning microscope, which suggested that siRNA delivered by PECLD-70 NPs/Cy5 siRNA complexes possessed of stronger capabilities in escaping from endosome/lysosome, entering the RNA-induced silencing complex (RISC) and cutting the target mRNA efficiently. The different siRNA release profile was dominated by the degradation rate of polyester segments. Therefore, it could be concluded that the adjustment of hydrophobic core of cationic nanoparticles could significantly affect their transfection behavior and appropriate polyester composition should be concerned in designing of analogous siRNA vectors.

Polymeric nanoparticles for targeted treatment in oncology: current insights

Chemotherapy, a major strategy for cancer treatment, lacks the specificity to localize the cancer therapeutics in the tumor site, thereby affecting normal healthy tissues and advocating toxic adverse effects. Nanotechnological intervention has greatly revolutionized the therapy of cancer by surmounting the current limitations in conventional chemotherapy, which include undesirable biodistribution, cancer cell drug resistance, and severe systemic side effects. Nanoparticles (NPs) achieve preferential accumulation in the tumor site by virtue of their passive and ligand-based targeting mechanisms. Polymer-based nanomedicine, an arena that entails the use of polymeric NPs, polymer micelles, dendrimers, polymersomes, polyplexes, polymer–lipid hybrid systems, and polymer–drug/protein conjugates for improvement in efficacy of cancer therapeutics, has been widely explored. The broad scope for chemically modifying the polymer into desired construct makes it a versatile delivery system. Several polymer-based therapeutic NPs have been approved for clinical use. This review provides an insight into the advances in polymer-based targeted nanocarriers with focus on therapeutic aspects in the field of oncology.

Fine-tuning thermoresponsive functional poly(ε-caprolactone)s to enhance micelle stability and drug loading

New caprolactone-based amphiphilic terpolymers feature thermoresponsive behavior, biodegradable backbones, and enhanced micelle stability.

Amphiphilic core cross-linked star polymers as water-soluble, biocompatible and biodegradable unimolecular carriers for hydrophobic drugs

We report a series of amphiphilic, unimolecular, biocompatible, biodegradable and readily functionalisable PEG-PCL-based CCS polymers formed in a well-controlled manner and their application as a carrier of hydrophobic anthracycline drugs.

Controlled release of anticancer drug Paclitaxel using nano-structured amphiphilic star-hyperbranched block copolymers

Two amphiphilic star-hyperbranched copolymers with different hydrophilic PHEMA segments were synthesized, and their drug loading/release profiles were examined by using Paclitaxel.