Enzyme-Triggered Degradation of Supramolecularly Cross-Linked Polymersomes of Azobenzene-Based Polyurethane: Cell-Selective Anticancer Drug Release

Enzyme-responsive self-assembled nanostructures for drug delivery applications have gained a lot of attention, as enzymes exhibit dysregulation in many disease-associated microenvironments. Azoreductase enzyme levels are strongly elevated in many tumor tissues; hence, here, we exploited the altered enzyme activity of the azoreductase enzyme and designed a main-chain azobenzene-based amphiphilic polyurethane, which self-assembles into a vesicular nanostructure and is programmed to disassemble in response to a specific enzyme, azoreductase, with the help of the nicotinamide adenine dinucleotide phosphate (NADPH) coenzyme in the hypoxic environment of solid tumors. The vesicular nanostructure sequesters, stabilizes the hydrophobic anticancer drug, and releases the drug in a controlled fashion in response to enzyme-triggered degradation of azo-bonds and disruption of vesicular assembly. The biological evaluation revealed tumor extracellular matrix pH-induced surface charge modulation, selective activated cellular uptake to azoreductase overexpressed lung cancer cells (A549), and the release of the anticancer drug followed by cell death. In contrast, the benign nature of the drug-loaded vesicular nanostructure toward normal cells (H9c2) suggested excellent cell specificity. We envision that the main-chain azobenzene-based polyurethane discussed in this manuscript could be considered as a possible selective chemotherapeutic cargo against the azoreductase overexpressed cancer cells while shielding the normal cells from off-target toxicity.

Photochemical [2 + 2] Cycloaddition Enables the Synthesis of Highly Thermally Stable and Acid/Base-Resistant Polyesters from a Nonpolymerizable α,β-Conjugated Valerolactone

We report a simple strategy to transform a nonpolymerizable six-membered α,β-conjugated lactone, 5,6-dihydro-2H-pyran-2-one (DPO), into polymerizable bicyclic lactones via photochemical [2 + 2] cycloaddition. Two bicyclic lactones, M1 and M2, were obtained by the photochemical [2 + 2] cycloaddition of tetramethylethylene and DPO. Ring-opening polymerization (ROP) of M1 and M2 catalyzed by diphenyl phosphate (DPP), La[N(SiMe3)2]3, and 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris (dimethylamino) phosphoranylide-namino]-2λ5, 4λ5-catenadi(phosphazene) (tBu-P4) were conducted. M1 is highly polymerizable, either DPP or La[N(SiMe3)2]3 could catalyze its living ROP under mild conditions, affording the well-defined PM1 with a predictable molar mass and low dispersity. M2 could only be polymerized with tBu-P4 as the catalyst, also generating the same polymer PM1. PM1 has high thermal stability, with a Td,5% being up to 376 °C. Ring-opening copolymerization (ROcP) of M1 and δ-valerolactone (δ-VL) catalyzed by La[N(SiMe3)2]3 afforded a series of random copolymers with enhanced thermal stabilities. Both PM1 and the copolymer containing 10 mol % M1 exhibited excellent resistance to acidic and basic hydrolysis. Our results demonstrate that direct photochemical [2 + 2] cycloaddition of α,β-conjugated valerolactone is not only a strategy to tune its polymerizability, but also allows for the synthesis of highly thermally stable aliphatic polyesters, inaccessible by other methods.

Maleimide functionalized polycaprolactone micelles for glutathione quenching and doxorubicin delivery

High glutathione production is known to be one of the defense mechanisms by which many cancer cells survive elevated oxidative stress. By explicitly targeting glutathione in these cancer cells and diminishing its levels, oxidative stress can be intensified, ultimately triggering apoptosis or programmed cell death. Herein, we developed a novel approach by creating maleimide-functionalized polycaprolactone polymers, specifically using 2,3-diiodomaleimide functionality to reduce the level of glutathione in cancer cells. Polycaprolactone was chosen to conjugate the 2,3-diiodomaleimide functionality due to its biodegradable and biocompatible properties. The amphiphilic block copolymer was synthesized using PEG as a macroinitiator to make corresponding polymeric micelles. The resulting 2,3-diiodomaleimide-conjugated polycaprolactone micelles effectively quenched glutathione, even at low concentrations (0.01 mg mL-1). Furthermore, we loaded these micelles with the anticancer drug doxorubicin (DOX), which exhibited pH-dependent drug release. We obtained a loading capacity (LC) of 3.5% for the micelles, one of the highest LC reported among functional PCL-based micelles. Moreover, the enhanced LC doesn't affect their release profile. Cytotoxicity experiments demonstrated that empty and DOX-loaded micelles inhibited cancer cell growth, with the DOX-loaded micelles displaying the highest cytotoxicity. The ability of the polymer to quench intracellular GSH was also confirmed. This approach of attaching maleimide to polycaprolactone polymers shows promise in depleting elevated glutathione levels in cancer cells, potentially improving cancer treatment efficacy.

Size- and Shape-controlled Biodegradable Polymer Brushes Based on l-Amino Acid for Intracellular Drug Delivery and Deep-Tissue Penetration

We report size- and shape-controlled polymer brushes based on l-amino acid bioresource and study the role of polymer topology on the enzymatic biodegradation and deep-tissue penetration under in vitro and in vivo. For this purpose, l-tyrosine-based propargyl-functionalized monomer is tailor-made and polymerized via solvent-free melt polycondensation strategy to yield hydrophobic and clickable biodegradable poly(ester-urethane)s. Postpolymerization click chemistry strategy is applied to make well-defined amphiphilic one-dimensional rodlike and three-dimensional spherical polymer brushes by merely varying the lengths of PEG-azides in the reaction. These core-shell polymer brushes are found to be nontoxic and nonhemolytic and capable of loading clinical anticancer drug doxorubicin and deep-tissue penetrable near-infrared biomarker IR-780. In vitro enzymatic drug-release kinetics and lysotracker-assisted real-time live-cell confocal bioimaging revealed that the rodlike polymer brush is superior than its spherical counterparts for faster cellular uptake and enzymatic biodegradation at the endolysosomal compartments to release DOX at the nucleus. Further, in vivo live-animal bioimaging by IVIS technique established that the IR-780-loaded rodlike polymer brush exhibited efficient deep-tissue penetration ability and emphasized the importance of polymer brush topology control for biological activity. Polymer brushes exhibit good stability in the blood plasma for more than 72 h, they predominately accumulate in the digestive organs like liver and kidney, and they are less toxic to heart and brain tissues. IVIS imaging of cryotome tissue slices of organs confirmed the deep-penetrating ability of the polymer brushes. The present investigation opens opportunity for bioderived and biodegradable polymer brushes as next-generation smart drug-delivery scaffolds.

Visible Light-Regulated Ring-Opening Polymerization of Lactones by Employing Indigo as a Photoacid Catalyst

The development of visible light-regulated polymerizations for precision synthesis of polymers has drawn considerable attention in the past years. In this study, an ancient dye, indigo, is successfully identified as a new and efficient photoacid catalyst, which can readily promote the ring-opening polymerization of lactones under visible light irradiation in a well-controlled manner, affording the desired polyester products with predictable molecular weights and narrow dispersity. The enhanced acidity of indigos by excitation is crucial to the H-bonding activation of the lactone monomers. Chain extension and block copolymer synthesis are also demonstrated with this method.

Effect of aromatic substituents on thermoresponsive functional polycaprolactone micellar carriers for doxorubicin delivery

Amphiphilic functional polycaprolactone (PCL) diblock copolymers are excellent candidates for micellar drug delivery. The functional groups on the backbone significantly affect the properties of PCL. A systematic investigation of the effect of aromatic substituents on the self-assembly of γ-functionalized PCLs and the delivery of doxorubicin (DOX) is presented in this work. Three thermoresponsive amphiphilic diblock copolymers with poly(γ-benzyloxy-ε-caprolactone) (PBnCL), poly(γ-phenyl- ε-caprolactone) (PPhCL), poly(γ-(4-ethoxyphenyl)-ε-caprolactone) (PEtOPhCL), respectively, as hydrophobic block and γ-tri(ethylene glycol) functionalized PCL (PME3CL) as hydrophilic block were prepared through ring-opening polymerization (ROP). The thermoresponsivity, thermodynamic stability, micelle size, morphology, DOX-loading, and release profile were determined. The LCST values of amphiphilic diblock copolymers PME3CL-b-PBnCL, PME3CL-b-PPhCL, and PME3CL-b-PEtOPhCL are 74.2°C, 43.3°C, and 37.3°C, respectively. All three copolymers formed spherical micelles in phosphate-buffered saline (PBS, 1×, pH = 7.4) at low concentrations ranging from 8.7 × 10-4 g/L to 8.9 × 10-4 g/L. PME3CL-b-PBnCL micelles showed the highest DOX loading capacity of 3.01 ± 0.18 (wt%) and the lowest drug release, while PME3CL-b-PEtOPhCL micelles exhibited the lowest DOX loading capacity of 1.95 ± 0.05 (wt%) and the highest drug release. Cytotoxicity and cellular uptake of all three micelles were assessed in vitro using MDA-MB-231 breast cancer cells. All three empty micelles did not show significant toxicity to the cells at concentrations high up to 0.5 mg/mL. All three DOX-loaded micelles were uptaken into the cells, and DOX was internalized into the nucleus of the cells.

Reversible Cross-linked Thermoresponsive Polycaprolactone Micelles for Enhanced Stability and Controlled Release

Thermoresponsive amphiphilic poly(ε-caprolactone)s (PCL)s are excellent candidates for drug delivery due to their biodegradability, biocompatibility, and controlled release. However, the thermoresponsivity of modified PCL can often lead to premature drug release because their lower critical solution temperature (LCST) is close to physiological temperature conditions. To address this issue, we developed a novel approach that involves functionalizing redox-responsive lipoic acid to the hydrophobic block of PCL. Lipoic acid has disulfide bonds that undergo reversible cross-linking after encapsulating the drug. Herein, we synthesized an ether-linked propargyl-substituted PCL as the hydrophobic block of an amphiphilic copolymer along with unsubstituted PCL. The propargyl group was used to attach lipoic acid through a postpolymerization modification reaction. The hydrophilic block is composed of an ether-linked, thermoresponsive tri(ethylene glycol)-substituted PCL. Anticancer drug doxorubicin (DOX) was encapsulated within the core of the micelles and induced cross-linking in the presence of a reducing agent, dithiothreitol. The developed micelles are thermodynamically stable and demonstrated thermoresponsivity with an LCST value of 37.5 °C but shifted to 40.5 °C after cross-linking. The stability and release of both uncross-linked (LA-PCL) and cross-linked (CLA-PCL) micelles were studied at physiological temperatures. The results indicated that CLA-PCL was stable, and only 35% release was observed after 46 h at 37 °C while LA-PCL released more than 70% drug at the same condition. Furthermore, CLA-PCL was able to release a higher amount of DOX in the presence of glutathione and above the LCST condition (42 °C). Cytotoxicity experiments revealed that CLA-PCL micelles are more toxic toward MDA-MB-231 breast cancer cells at 42 °C than at 37 °C, which supported the thermoresponsive release of the drug. These results indicate that the use of reversible cross-linking is a great approach toward synthesizing stable thermoresponsive micelles with reduced premature drug leakage.

Organocatalyzed ring-opening reactions of γ-carbonyl-substituted ε-caprolactones

Side-chain-functionalized aliphatic polyesters are promising as functional biodegradable polymers. We have investigated ring-opening reactions of γ-carbonyl-substituted ε-caprolactones (gCCLs) to obtain poly(ε-caprolactone) (PCL) analogues. Organic catalysts and Sn(Oct)2 often used for the ring-opening polymerization (ROP) of ε-caprolactone (CL) have been explored to find the conditions for the formation of polymeric products of gCCLs. We confirmed the consumption of gCCLs in all catalyzed reactions. However, chain propagation hardly occurs, as the propagating species are preferentially transformed to α-substituted five-membered lactones when the substituents are linked by ester or not sterically hindered. Intramolecular cyclization to form thermodynamically stable five-membered lactones releases alcohols and amines, serving as nucleophiles for the subsequent ring opening of other gCCLs. Thus, apparent chain reactions are realized for continuous consumption of gCCLs. The reaction preference remains unchanged independent of the catalysts, although the reactions of the amide-linked gCCLs by acidic catalysts are slightly mitigated. Finally, copolymerization of CL and a gCCL catalyzed by diphenyl phosphate has been investigated, which enables the chain propagation reaction to yield the linear oligomers of PCL analogues containing up to 16 mol% of gCCL units. This study contributes to understanding the chemistry of ring-opening reactions of substituted lactones for designing functional degradable polymers.

Recent Advances in Polycaprolactones for Anticancer Drug Delivery

Poly(ε-Caprolactone)s are biodegradable and biocompatible polyesters that have gained considerable attention for drug delivery applications due to their slow degradation and ease of functionalization. One of the significant advantages of polycaprolactone is its ability to attach various functionalities to its backbone, which is commonly accomplished through ring-opening polymerization (ROP) of functionalized caprolactone monomer. In this review, we aim to summarize some of the most recent advances in polycaprolactones and their potential application in drug delivery. We will discuss different types of polycaprolactone-based drug delivery systems and their behavior in response to different stimuli, their ability to target specific locations, morphology, as well as their drug loading and release capabilities.

Melt Polycondensation Strategy for Amide-Functionalized l-Aspartic Acid Amphiphilic Polyester Nano-assemblies and Enzyme-Responsive Drug Delivery in Cancer Cells

Aliphatic polyesters are intrinsically enzymatic-biodegradable, and there is ever-increasing demand for safe and smart next-generation biomaterials including drug delivery nano-vectors in cancer research. Using bioresource-based biodegradable polyesters is one of the elegant strategies to meet this requirement; here, we report an l-amino acid-based amide-functionalized polyester platform and explore their lysosomal enzymatic biodegradation aspects to administrate anticancer drugs in cancer cells. l-Aspartic acid was chosen and different amide-side chain-functionalized di-ester monomers were tailor-made having aromatic, aliphatic, and bio-source pendant units. Under solvent-free melt polycondensation methodology; these monomers underwent polymerization to yield high molecular weight polyesters with tunable thermal properties. PEGylated l-aspartic monomer was designed to make thermo-responsive amphiphilic polyesters. This amphiphilic polyester was self-assembled into a 140 ± 10 nm-sized spherical nanoparticle in aqueous medium, which exhibited lower critical solution temperature at 40-42 °C. The polyester nano-assemblies showed excellent encapsulation capabilities for anticancer drug doxorubicin (DOX), anti-inflammatory drug curcumin, biomarkers such as rose bengal (RB), and 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt. The amphiphilic polyester NP was found to be very stable under extracellular conditions and underwent degradation upon exposure to horse liver esterase enzyme in phosphate-buffered saline at 37 °C to release 90% of the loaded cargoes. Cytotoxicity studies in breast cancer MCF 7 and wild-type mouse embryonic fibroblasts cell lines revealed that the amphiphilic polyester was non-toxic to cell lines up to 100 μg/mL, while their drug-loaded polyester nanoparticles were able to inhibit the cancerous cell growth. Temperature-dependent cellular uptake studies further confirmed the energy-dependent endocytosis of polymer NPs across the cellular membranes. Confocal laser scanning microscopy assisted time-dependent cellular uptake analysis directly evident for the endocytosis of DOX loaded polymer NP and their internalization for biodegradation. In a nutshell, the present investigation opens up an avenue for the l-amino acid-based biodegradable polyesters from l-aspartic acids, and the proof of concept is demonstrated for drug delivery in the cancer cell line.

Organocatalytic Ring-Opening Polymerization of ϵ-Caprolactone with Phosphoramidimidates (PADIs) as a Bifunctional Brønsted Acid Catalyst

In this study, an organocatalytic ring-opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL) has been developed by employing PADIs as a novel and efficient acid/base bifunctional organocatalyst, which could afford metal-free poly(ϵ-caprolactone) with predictable molecular weight and narrow dispersity at a low catalyst loading under mild conditions. NMR and kinetic studies indicate that the ring-opening polymerizations of lactones catalyzed by PADIs proceed in a living and well controlled manner. Moreover, this organic Brønsted acid catalytic system could allow the synthesis of PCL with molecular weight above 60 kg/mol, as well as well-defined star polymers.

Microfluidic Synthesis of Block Copolymer Micelles: Application as Drug nanocarriers and as Photothermal Transductors When Loading Pd Nanosheets

The synthesis of polymeric nanoparticles from a block copolymer based on poly(ethylene glycol) and a polymethacrylate containing the nucleobase analogue 2,6-diacylaminopyridine has been optimized by microfluidics to obtain homogeneous spherical micelles. Loading and delivery properties have been studied using naproxen as a model. The incorporation of a Pd precursor in the polymer organic solution fed into the micromixer allows the preparation of Pd(II) precursor-polymer hybrid systems, and the subsequent reduction with CO lead to the in-situ synthesis of Pd nanosheets inside of the hydrophobic core of the polymeric micelles. This methodology is highly efficient to yield all polymeric nanoparticles loaded with Pd nanosheets as detected by electron microscopy and energy-dispersive X-ray spectroscopy. The cell viability of these Pd nanosheets-containing polymeric nanoparticles has been evaluated using five cell lines, showing a high cytocompatibility at the tested concentrations without detrimental effects in cell membrane and nuclei. Furthermore, the use of these hybrid polymeric nanoparticles as photothermal transductors has been evaluated using NIR as irradiation source, as well as its application in photothermal therapy using different cell lines demonstrating a high efficiency in all cell cultures. This article is protected by copyright. All rights reserved.

Fluorescent ABC-Triblock Polymer Nanocarrier for Cisplatin Delivery to Cancer Cells

Monitoring intracellular administration of non-luminescent anticancer drugs like cisplatin is a very challenging task in cancer research. Perylenebisimide (PBI) chromophore tagged fluorescent ABC-triblock polycaprolactone (PCL) nanoscaffold was engineered having carboxylic acid blocks for the chemical conjugation of cisplatin at the core and hydrophilic PEG blocks at the periphery. The amphiphilic ABC triblock Pt-prodrug was self-assembled into < 200 nm nanoparticles and exhibited excellent shielding against drug detoxification by the glutathione (GSH) species in the cytosol. In vitro drug release studies confirmed that the Pt-prodrug was stable at extracellular conditions and the PCL block exclusively underwent lysosomal-enzymatic biodegradation at the intracellular level to release the cisplatin drug in the active-form for accomplishing more than 90% cell growth inhibition. Confocal microscopic imaging of the red-fluorescence signals from the perylene chromophores established the simultaneous monitoring and delivery aspects of Pt-prodrug, and the proof-of-concept was successfully demonstrated in breast and cervical cancer cell lines.

Hyperbranched vs. linear poly(disulfide) for intracellular drug delivery

This communication reports comparative studies between amphiphilic hyperbranched and linear poly(disulfide) with regard to their aggregation and glutathione-responsive intracellular drug delivery.

Shape-Dependent Cellular Uptake of Nanostructures Produced from Supramolecular Structure-Directing Unit-Appended Hydrophilic Polymers

Cellular uptake is an important event in drug delivery and other biomedical applications. Amphiphilic polymers produce aggregates of different size and shape depending on the intrinsic structural differences and the packing parameter. Although they have been explored for various biomedical applications with immense interest, the relationship between the shape of the aggregate and cellular uptake has been studied only in limited examples. This work reports two polymers (P1 and P2), both of which contain a hydrophobic supramolecular structure-directing unit (SSDU) at the chain-end of a fluorescence dye-labeled hydrophilic polymer. Depending on the difference in the structure of the single H-bonding functional group (hydrazide or amide) of the SSDU, P1 and P2 produce polymersomes (NS1) and spherical micelles (NS2), respectively. An aged solution of P2 produces cylindrical micelles (NS3). Confocal microscopy studies reveal that the uptake of these nanostructures in HeLa cells greatly depends on the shape of the aggregate. Spherical NS1 and NS2 show appreciable uptake at 1 or 4 h of incubation, whereas NS3 shows negligible uptake. Temperature-dependent cellular uptake studies reveal an energy-dependent endocytosis pathway. Kinetic studies show gradual increase in the cellular uptake with time, and at 24 h the relative uptake ratio (NS1:NS2:NS3) is 1.0:0.2:<0.1, implying the polymersome morphology (NS1) is most efficient for cellular uptake compared to the spherical or cylindrical micelles. The same trend was also noticed for MDA-MB 231 cells. Confocal microscopy studies further reveal cellular internalization and intracellular location of NS1, which showed maximum cellular uptake. As the intrinsic difference in the chemical structure of the two polymers is negligible, the observed difference can be explicitly assigned to their difference in shape.

Synthesis of Functionalized Aliphatic Acid Esters via the Generation of Alkyl Radicals from Silylperoxyacetals

We describe a catalytic method for the synthesis of a variety of functionalized aliphatic acid esters using silylperoxyacetals, which are versatile alkyl radical precursors with a terminal ester moiety. In the presence of an appropriate transition-metal catalyst, the in situ generation of alkyl radicals and the subsequent bond-forming process proceeds smoothly to afford synthetically valuable aliphatic acid derivatives. The present method can be applied to the efficient synthesis of a pharmaceutically important 1,1-diarylalkane motif. In addition, a novel strategy for the synthesis of structurally diverse hydroxy acid derivatives via a C-O bond formation process that utilizes TEMPO has been developed.

Linear and Branched Lactide Polymers for Targeted Drug Delivery Systems

Abstract

The review presents modern advances in the synthesis of biodegradable polymers based on lactide of various topologies and also analyzes the main methods for preparation of nanoparticles that show promise for the creation of targeted drug delivery systems.

Supramolecular Functionalizable Linear-Dendritic Block Copolymers for the Preparation of Nanocarriers by Microfluidics

Hybrid linear-dendritic block copolymers (LDBCs) having dendrons with a precise number of peripheral groups that are able to supramolecular bind functional moieties are challenging materials as versatile polymeric platforms for the preparation of functional polymeric nanocarriers. PEG2k-b-dxDAP LDBCs that are based on polyethylene glycol (PEG) as hydrophilic blocks and dendrons derived from bis-MPA having 2,6-diacylaminopyridine (DAP) units have been efficiently synthesized by the click coupling of preformed blocks, as was demonstrated by spectroscopic techniques and mass spectrometry. Self-assembly ability was first checked by nanoprecipitation. A reproducible and fast synthesis of aggregates was accomplished by microfluidics optimizing the total flow rate and phase ratio to achieve spherical micelles and/or vesicles depending on dendron generation and experimental parameters. The morphology and size of the self-assemblies were studied by TEM, Cryogenic Transmission Electron Microscopy (cryo-TEM), and Dynamic Light Scattering (DLS). The cytotoxicity of aggregates synthesized by microfluidics and the influence on apoptosis and cell cycle evaluation was studied on four cell lines. The self-assemblies are not cytotoxic at doses below 0.4 mg mL-1. Supramolecular functionalization using thymine derivatives was explored for reversibly cross-linking the hydrophobic blocks. The results open new possibilities for their use as drug nanocarriers with a dynamic cross-linking to improve nanocarrier stability but without hindering disassembly to release molecular cargoes.

Neodymium catalysts for polymerization of dienes, vinyl monomers, and ε-caprolactone

This review discusses various neodymium catalysts for stereospecific polymerization of dienes, vinyl monomers, and ε-caprolactone.

Smooth Muscle Cell Responses to Poly(ε-Caprolactone) Triacrylate Networks with Different Crosslinking Time

Poly(ε-caprolactone) triacrylate (PCLTA) is attractive in tissue engineering because of its good biocompatibility and processability. The crosslinking time strongly influences PCLTAs cellular behaviors. To investigate these influences, PCLTAs with different molecular weights were crosslinked under UV light for times ranging from 1 to 20 min. The crosslinking efficiency of PCLTA increased with decreasing the molecular weight and increasing crosslinking time which could increase the gel fraction and network stiffness and decrease the swelling ratio. Then, the PCLTA networks crosslinked for different time were used as substrates for culturing rat aortic smooth muscle cells (SMCs). SMC attachment and proliferation all increased when the PCLTA molecular weight increased from 8k to 10k and then to 20k at the same crosslinking time. For the same PCLTA, SMC attachment, proliferation, and focal adhesions increased with increasing the crosslinking time, in particular, between the substrates crosslinked for less than 3 min and longer than 5 min. This work will provide a good experimental basis for the application of PCLTA.

Amphiphilic mannose-6-phosphate glycopolypeptide-based bioactive and responsive self-assembled nanostructures for controlled and targeted lysosomal cargo delivery

Receptors of carbohydrate mannose-6-phosphate (M6P) are overexpressed in specific cancer cells (such as breast cancer) and are also involved in the trafficking of mannose-6-phosphate labeled proteins exclusively onto lysosomes via cell surface M6P receptor (CI-MPR) mediated endocytosis. Herein, for the first time, mannose-6-phosphate glycopolypeptide (^M6PGP)-based bioactive and stimuli-responsive nanocarriers are reported. They are selectively taken up via receptor-mediated endocytosis, and trafficked to lysosomes where they are subsequently degraded by pH or enzymes, leading to the release of the cargo inside the lysosomes. Two different amphiphilic M6P block copolymers ^M6PGP₁₅-^APPO₄₄ and ^M6PGP₁₅-(PCL₂₅)₂ were synthesized by click reaction of the alkyne end-functionalized ^M6PGP₁₅ with pH-responsive biocompatible azide end-functionalized acetal PPO and azide end-functionalized branched PCL, respectively. In water, the amphiphilic M6P-glycopolypeptide block copolymers self-assembled into micellar nanostructures, as was evidenced by DLS, TEM, AFM, and fluorescence spectroscopy techniques. These micellar systems were competent to encapsulate the hydrophobic dye rhodamine-B-octadecyl ester, which was used as the model drug. They were stable at physiological pH but were found to disassemble at acidic pH (for ^M6PGP₁₅-^APPO₄₄) or in the presence of esterase (for ^M6PGP₁₅-(PCL₂₅)₂). These ^M6PGP based micellar nanoparticles can selectively target lysosomes in cancerous cells such as MCF-7 and MDA-MB-231. Finally, we demonstrate the clathrin-mediated endocytic pathway of the native FL-^M6PGP polymer and RBOE loaded ^M6PGP micellar-nanocarriers, and selective trafficking of MCF-7 and MDA-MB-231 breast cancer cell lysosomes, demonstrating their potential applicability toward receptor-mediated lysosomal cargo delivery.

Polymeric micelles for the delivery of poorly soluble drugs: From nanoformulation to clinical approval

Over the last three decades, polymeric micelles have emerged as a highly promising drug delivery platform for therapeutic compounds. Particularly, poorly soluble small molecules with high potency and significant toxicity were encapsulated in polymeric micelles. Polymeric micelles have shown improved pharmacokinetic profiles in preclinical animal models and enhanced efficacy with a superior safety profile for therapeutic drugs. Several polymeric micelle formulations have reached the clinical stage and are either in clinical trials or are approved for human use. This furthers interest in this field and underscores the need for additional learning of how to best design and apply these micellar carriers to improve the clinical outcomes of many drugs. In this review, we provide detailed information on polymeric micelles for the solubilization of poorly soluble small molecules in topics such as the design of block copolymers, experimental and theoretical analysis of drug encapsulation in polymeric micelles, pharmacokinetics of drugs in polymeric micelles, regulatory approval pathways of nanomedicines, and current outcomes from micelle formulations in clinical trials. We aim to describe the latest information on advanced analytical approaches for elucidating molecular interactions within the core of polymeric micelles for effective solubilization as well as for analyzing nanomedicine's pharmacokinetic profiles. Taking into account the considerations described within, academic and industrial researchers can continue to elucidate novel interactions in polymeric micelles and capitalize on their potential as drug delivery vehicles to help improve therapeutic outcomes in systemic delivery.

Double hydrophilic block copolymers self-assemblies in biomedical applications

Double-hydrophilic block copolymers (DHBCs), consisting of at least two different water-soluble blocks, are an alternative to the classical amphiphilic block copolymers and have gained increasing attention in the field of biomedical applications. Although the chemical nature of the two blocks can be diverse, most classical DHBCs consist of a bioeliminable non-ionic block to promote solubilization in water, like poly(ethylene glycol), and a second block that is more generally a pH-responsive block capable of interacting with another ionic polymer or substrate. This second block is generally non-degradable and the presence of side chain functional groups raises the question of its fate and toxicity, which is a limitation in the frame of biomedical applications. In this review, following a first part dedicated to recent examples of non-degradable DHBCs, we focus on the DHBCs that combine a biocompatible and bioeliminable non-ionic block with a degradable functional block including polysaccharides, polypeptides, polyesters and other miscellaneous polymers. Their use to design efficient drug delivery systems for various biomedical applications through stimuli-dependent self-assembly is discussed along with the current challenges and future perspectives for this class of copolymers.

Poly(ε-caprolactone) with pH and UCST responsiveness as a 5-fluorouracil carrier

Stimuli-responsive polymers with excellent biocompatibility and biodegradability are highly demanded as carriers for controlled drug delivery.

A Modular Coassembly Approach to All-In-One Multifunctional Nanoplatform for Synergistic Codelivery of Doxorubicin and Curcumin

Synergistic combination therapy by integrating chemotherapeutics and chemosensitizers into nanoparticles has demonstrated great potential to reduce side effects, overcome multidrug resistance (MDR), and thus improve therapeutic efficacy. However, with regard to the nanocarriers for multidrug codelivery, it remains a strong challenge to maintain design simplicity, while incorporating the desirable multifunctionalities, such as coloaded high payloads, targeted delivery, hemodynamic stability, and also to ensure low drug leakage before reaching the tumor site, but simultaneously the corelease of drugs in the same cancer cell. Herein, we developed a facile modular coassembly approach to construct an all-in-one multifunctional multidrug delivery system for the synergistic codelivery of doxorubicin (DOX, chemotherapeutic agent) and curcumin (CUR, MDR modulator). The acid-cleavable PEGylated polymeric prodrug (DOX-h-PCEC), tumor cell-specific targeting peptide (CRGDK-PEG-PCL), and natural chemosensitizer (CUR) were ratiometrically assembled into in one single nanocarrier (CUR/DOX-h-PCEC@CRGDK NPs). The resulting CUR/DOX-h-PCEC@CRGDK NPs exhibited several desirable characteristics, such as efficient and ratiometric drug loading, high hemodynamic stability and low drug leakage, tumor intracellular acid-triggered cleavage, and subsequent intracellular simultaneous drug corelease, which are expected to maximize a synergistic effect of chemotherapy and chemosensitization. Collectively, the multifunctional nanocarrier is feasible for the creation of a robust nanoplatform for targeted multidrug codelivery and efficient MDR modulation.

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.

ROS-responsive poly(ε-caprolactone) with pendent thioether and selenide motifs

Synthesis and oxidation properties of three chalcogen-containing ROS-responsive poly(ε-caprolactone)s have been reported.

A twin-tailed tadpole-shaped amphiphilic copolymer of poly(ethylene glycol) and cyclic poly(ε-caprolactone): synthesis, self-assembly and biomedical applications

A tadpole-shaped amphiphilic copolymer containing cyclic PCL and two PEG tails, PEG-b-(c-PCL)-b-PEG, was rationally designed and synthesized.

Strategies to combine ROP with ATRP or RAFT polymerization for the synthesis of biodegradable polymeric nanoparticles for biomedical applications

The available strategies to combine CRPs and ROP in the synthesis of highly engineered polymer nanoparticles are here critically discussed.

Improvement in aluminum complexes bearing a Schiff base in ring-opening polymerization of ε-caprolactone: the synergy of the N,S-Schiff base in a five-membered ring aluminum system

A series of five-membered ring aluminum complexes bearing thiol-Schiff base ligands were synthesized, and their application in the ring-opening polymerization of ε-caprolactone (CL) was investigated.

An enzymatic method for the production of 6-oxohexanoic acid from 6-aminohexanoic acid by an enzyme oxidizing ω-amino compounds from Phialemonium sp. AIU 274

An enzymatic method for 6-oxohexanoic acid production was developed using 6-aminohexanoic acid and an ω-amino group-oxidizing enzyme (ω-AOX) from Phialemonium sp. AIU 274. 6-Oxohexanoic acid was produced from 6-aminohexanoic acid with 100% yield by incubation with 0.3 U of the ω-AOX and 20 U of catalase at 30 °C for 30 h in 0.1 M potassium phosphate buffer (pH 7.0).

Mono-BHT heteroleptic magnesium complexes: synthesis, molecular structure and catalytic behavior in the ring-opening polymerization of cyclic esters

Numerous heteroleptic 2,6-di-tert-butyl-4-methylphenolate (BHT) magnesium complexes have been synthesized by treatment of (BHT)MgBu(THF)₂ with various alcohols. Molecular structures of the complexes have been determined by X-ray diffraction. The magnesium coordination number in [(BHT)Mg(μ-OBn)(THF)]₂ (3) and [(BHT)Mg(μ-O-tert-BuC₆H₄)(THF)]₂ (4) is equal to 4. Complexes formed from esters of glycolic and lactic acids, [(BHT)Mg(μ-OCH₂COOEt)(THF)]₂ (5) and [(BHT)Mg(μ-OCH(CH₃)COOCH₂COO^tBu)(THF)]₂ (6) contain chelate fragments with pentacoordinated magnesium. Compounds 3-6 contain THF molecules coordinated to magnesium atoms. Complex {(BHT)Mg[μ-O(CH₂)₃CON(CH₃)₂]}₂ (7) does not demonstrate any tendency to form an adduct with THF. It has been experimentally determined that complexes 3 and 5 are highly active catalysts of lactide polymerization. The activity of 4 is rather low, and complex 7 demonstrates moderate productivity. According to DOSY NMR experiments, compounds 3 and 5 retain their dimeric structures even in THF. The free energies of model dimeric [(DBP)Mg(μ-OMe)(Sub)]₂ and monomeric (DBP)Mg(OMe)(Sub)₂ products on treatment of [(DBP)Mg(μ-OMe)(THF)]₂ with a series of σ-electron donors (Sub) have been estimated by DFT calculations. These results demonstrate that the substitution of THF by Sub in a dimeric molecule is an energetically allowed process, whereas the dissociation of dimers is energetically unfavorable. DFT modeling of ε-CL and (dl)-lactide ROP catalyzed by dimeric and monomeric complexes showed that a cooperative effect of two magnesium atoms occurs within the ROP for binuclear catalytic species. A comparison of the reaction profiles for ROP catalyzed by binuclear and mononuclear species allowed us to conclude that the binuclear mechanism is favorable in early stages of ROP initiated by dimers 3 and 5.