Manipulation of Macrophage Uptake by Controlling the Aspect Ratio of Graft Copolymer Micelles

Nanostructures of drug carriers play a crucial role in nanomedicine due to their ability to influence drug delivery. There is yet no clear consensus regarding the optimal size and shape (e.g., aspect ratio) of nanoparticles for minimizing macrophage uptake, given the difficulties in controlling the shape and size of nanoparticles while maintaining identical surface properties. Here, we employed graft copolymer self-assembly to prepare polymer micelles with aspect ratios ranging from 1.0 (spherical) to 10.8 (cylindrical) and closely matched interfacial properties. Notably, our findings emphasize that cylindrical micelles with an aspect ratio of 2.4 are the least susceptible to macrophage uptake compared with both their longer counterparts and spherical micelles. This reduced uptake of the short cylindrical micelles results in a 3.3-fold increase in blood circulation time compared with their spherical counterparts. Controlling the aspect ratio of nanoparticles is crucial for improving drug delivery efficacy through better nanoparticle design.

Protein Delivery to the Cytosol and Cell Nucleus via Micellar Nanocarrier-Based Nonendocytic Uptake

Although efficient cell nucleus delivery of exogenous materials can greatly improve their biochemical activity, this is strictly restricted by cellular uptake and intracellular trafficking processes. In the current approach, synthetic carriers are designed for cell delivery of exogenous materials via endocytosis, and nucleus delivery can be achieved via endosomal escape. Here, we demonstrate that a nonendocytic cell uptake approach can be adapted for protein delivery to the cell nucleus. We have designed a phenylboronic acid-terminated micellar carrier that can bind with protein in the presence of green tea polyphenol and deliver protein into the cytosol via the nonendocytic approach. Using this approach, four different proteins are delivered to the cytosol within 15 min, and low-molecular weight proteins are delivered to the nucleus. The designed approach can be extended for delivering macromolecular drugs to subcellular targets for a more efficient therapy.

Nano-calcipotriol as a potent anti-hepatic fibrosis agent

Calcipotriol (CAL) has been widely studied as a fibrosis inhibitor and used to treat plaque psoriasis via transdermal administration. The clinical application of CAL to treat liver fibrosis is bottlenecked by its unsatisfactory pharmacokinetics, biodistribution, and side effects, such as hypercalcemia in patients. The exploration of CAL as a safe and effective antifibrotic agent remains a major challenge. Therefore, we rationally designed and synthesized a self-assembled drug nanoparticle encapsulating CAL in its internal hydrophobic core for systematic injection (termed NPs/CAL) and further investigated the beneficial effect of the nanomaterial on liver fibrosis. C57BL/6 mice were used as the animal model, and human hepatic stellate cell line LX-2 was used as the cellular model of hepatic fibrogenesis. Immunofluorescence staining, flow cytometry, western blotting, immunohistochemical staining, and in vitro imaging were used for evaluating the efficacy of NPs/CAL treatment. We found NPs/CAL can be quickly internalized in vitro, thus potently deactivating LX-2 cells. In addition, NPs/CAL improved blood circulation and the accumulation of CAL in liver tissue. Importantly, NPs/CAL strongly contributed to the remission of liver fibrosis without inducing hypercalcemia. Overall, our work identifies a promising paradigm for the development of nanomaterial-based agents for liver fibrosis therapy.

Nuclear Transport of the Molecular Drug via Nanocarrier-Based Nonendocytic Cellular Uptake

Although subcellular targeting can enhance the therapeutic performance of most drugs, such targeting requires appropriate carrier-based delivery that can bypass endosomal/lysosomal trafficking. Recent works show that nanocarriers can be designed for direct cell membrane translocation and nonendocytic uptake, bypassing the usual endocytosis processes. Here we show that this approach can be adapted for the rapid cell nucleus delivery of molecular drugs. In particular, a guanidinium-terminated nanocarrier is used to create a weak interaction-based carrier-drug nanoassembly for direct membrane translocation into the cytosol. The rapid and extensive entry of a drug-loaded nanocarrier into the cell without any vesicular coating and affinity of the drug to the nucleus allows their nucleus labeling. Compared to endocytotic uptake that requires more than hours for cell uptake followed by predominant lysosomal entrapment, this nonendocytic uptake labels the nucleus within a few minutes without any lysosomal trafficking. This approach may be utilized for nanocarrier-based subcellular targeting of drugs for more effective therapy.

RAFT Synthesis and Characterization of Poly(Butyl-co-2-(N,N-Dimethylamino)Ethyl Acrylates)-block-Poly(Polyethylene Glycol Monomethyl Ether Acrylate) as a Photosensitizer Carrier for Photodynamic Therapy

Polymer micelles are promising drug delivery systems for highly hydrophobic photosensitizers in photodynamic therapy (PDT) applications. We previously developed pH-responsive polymer micelles consisting of poly(styrene-co-2-(N,N-dimethylamino)ethyl acrylate)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(St-co-DMAEA)-b-PPEGA) for zinc phthalocyanine (ZnPc) delivery. In this study, poly(butyl-co-2-(N,N-dimethylamino)ethyl acrylates)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(BA-co-DMAEA)-b-PPEGA) was synthesized via reversible addition and fragmentation chain transfer (RAFT) polymerization to explore the role of neutral hydrophobic units in photosensitizer delivery. The composition of DMAEA units in P(BA-co-DMAEA) was adjusted to 0.46, which is comparable to that of P(St-co-DMAEA)-b-PPEGA. The size distribution of the P(BA-co-DMAEA)-b-PPEGA micelles changed when the pH decreased from 7.4 to 5.0, indicating their pH-responsive ability. The photosensitizers, 5,10,15,20-tetrakis(pentafluorophenyl)chlorin (TFPC), 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TFPP), protoporphyrin IX (PPIX), and ZnPc were examined as payloads for the P(BA-co-DMAEA)-b-PPEGA micelles. The encapsulation efficiency depended on the nature of the photosensitizer. TFPC-loaded P(BA-co-DMAEA)-b-PPEGA micelles exhibited higher photocytotoxicity than free TFPC in the MNNG-induced mutant of the rat murine RGM-1 gastric epithelial cell line (RGK-1), indicating their superiority for photosensitizer delivery. ZnPc-loaded P(BA-co-DMAEA)-b-PPEGA micelles also exhibited superior photocytotoxicity compared to free ZnPc. However, their photocytotoxicity was lower than that of P(St-co-DMAEA)-b-PPEGA. Therefore, neutral hydrophobic units, as well as pH-responsive units, must be designed for the encapsulation of photosensitizers.

Poly(caprolactone)-b-poly(ethylene glycol)-Based Polymeric Micelles as Drug Carriers for Efficient Breast Cancer Therapy: A Systematic Review

Recently, drug delivery systems based on nanoparticles for cancer treatment have become the centre of attention for researchers to design and fabricate drug carriers for anti-cancer drugs due to the lack of tumour-targeting activity in conventional pharmaceuticals. Poly(caprolactone)-b-poly(ethylene glycol) (PCL-PEG)-based micelles have attracted significant attention as a potential drug carrier intended for human use. Since their first discovery, the Food and Drug Administration (FDA)-approved polymers have been studied extensively for various biomedical applications, specifically cancer therapy. The application of PCL-PEG micelles in different cancer therapies has been recorded in countless research studies for their efficacy as drug cargos. However, systematic studies on the effectiveness of PCL-PEG micelles of specific cancers for pharmaceutical applications are still lacking. As breast cancer is reported as the most prevalent cancer worldwide, we aim to systematically review all available literature that has published research findings on the PCL-PEG-based micelles as drug cargo for therapy. We further discussed the preparation method and the anti-tumour efficacy of the micelles. Using a prearranged search string, Scopus and Science Direct were selected as the databases for the systematic searching strategy. Only eight of the 314 articles met the inclusion requirements and were used for data synthesis. From the review, all studies reported the efficiency of PCL-PEG-based micelles, which act as drug cargo for breast cancer therapy.

Amphiphilic Block Copolymers: Their Structures, and Self-Assembly to Polymeric Micelles and Polymersomes as Drug Delivery Vehicles

Self-assembly of amphiphilic block copolymers display a multiplicity of nanoscale periodic patterns proposed as a dominant tool for the 'bottom-up' fabrication of nanomaterials with different levels of ordering. The present review article focuses on the recent updates to the self-association of amphiphilic block copolymers in aqueous media into varied core-shell morphologies. We briefly describe the block copolymers, their types, microdomain formation in bulk and micellization in selective solvents. We also discuss the characteristic features of block copolymers nanoaggregates viz., polymer micelles (PMs) and polymersomes. Amphiphilic block copolymers (with a variety of hydrophobic blocks and hydrophilic blocks; often polyethylene oxide) self-assemble in water to micelles/niosomes similar to conventional nonionic surfactants with high drug loading capacity. Double hydrophilic block copolymers (DHBCs) made of neutral block-neutral block or neutral block-charged block can transform one block to become hydrophobic under the influence of a stimulus (physical/chemical/biological), and thus induced amphiphilicity and display self-assembly are discussed. Different kinds of polymer micelles (viz. shell and core-cross-linked, core-shell-corona, schizophrenic, crew cut, Janus) are presented in detail. Updates on polymerization-induced self-assembly (PISA) and crystallization-driven self-assembly (CDSA) are also provided. Polyion complexes (PICs) and polyion complex micelles (PICMs) are discussed. Applications of these block copolymeric micelles and polymersomes as nanocarriers in drug delivery systems are described.

Nontoxic N-Heterocyclic Olefin Catalyst Systems for Well-Defined Polymerization of Biocompatible Aliphatic Polycarbonates

Herein, N-heterocyclic olefins (NHOs) are utilized as catalysts for the ring-opening polymerization (ROP) of functional aliphatic carbonates. This emerging class of catalysts provides high reactivity and rapid conversion. Aiming for the polymerization of monomers with high side chain functionality, six-membered carbonates derived from 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) served as model compounds. Tuning the reactivity of NHO from predominant side chain transesterification at room temperature toward ring-opening at lowered temperatures (-40 °C) enables controlled ROP. These refined conditions give narrowly distributed polymers of the hydrophobic carbonate 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MTC-OBn) (Đ < 1.30) at (pseudo)first-order kinetic polymerization progression. End group definition of these polymers demonstrated by mass spectrometry underlines the absence of side reactions. For the active ester monomer 5-methyl-5-pentafluorophenyloxycarbonyl-1,3-dioxane-2-one (MTC-PFP) with elevated side chain reactivity, a cocatalysis system consisting of NHO and the Lewis acid magnesium iodide is required to retune the reactivity from side chains toward controlled ROP. Excellent definition of the products (Đ < 1.30) and mass spectrometry data demonstrate the feasibility of this cocatalyst approach, since MTC-PFP has thus far only been polymerized successfully using acidic catalysts with moderate control. The broad feasibility of our findings was further demonstrated by the synthesis of block copolymers for bioapplications and their successful nanoparticular assembly. High tolerability of NHO in vitro with concentrations ranging up to 400 μM (equivalent to 0.056 mg/mL) further emphasize the suitability as a catalyst for the synthesis of bioapplicable materials. The polycarbonate block copolymer mPEG₄₄-b-poly(MTC-OBn) enables physical entrapment of hydrophobic dyes in sub-20 nm micelles, whereas the active ester block copolymer mPEG₄₄-b-poly(MTC-PFP) is postfunctionalizable by covalent dye attachment. Both block copolymers thereby serve as platforms for physical or covalent modification of nanocarriers for drug delivery.

Amphiphilic Liquid Crystalline Polymer Micelles That Exhibit a Phase Transition at Body Temperature

Liquid crystalline polymers (LCPs), which exhibit unique structures and properties intermediate between those of liquids and solids, are widely utilized as functional and advanced materials for fabricating optical devices and high-performance fibers. This utility stems from their ability to abruptly change their organized structures and mobilities at their liquid crystalline-isotropic phase transition temperatures, similar to the properties of biological membranes. Despite these numerous potential applications of LCPs, no study on their use in medical applications such as drug delivery has been reported. In the present study, we synthesized amphiphilic side-chain LCPs (LCP-g-OEGs, where OEG is oligo(ethylene glycol)) for medical applications, where the LCP-g-OEGs undergo a nematic-isotropic phase transition at body temperature. The LCP-g-OEGs formed micelles with a diameter of approximately 130 nm in aqueous media. The micelles were stable and did not dissociate in aqueous media even when the temperature exceeded the nematic-isotropic phase transition temperature (T_NI). Although the release of a dye as a model drug from micelles was suppressed at temperatures lower than T_NI, their dye release was drastically enhanced at temperatures higher than T_NI. The LCP-g-OEG micelles regulated dye release reversibly in accordance with stepwise changes in temperature, without undergoing dissociation, differing from the behavior of standard temperature-responsive micelles. The temperature-responsive dye release behavior is induced by dramatic changes in their well-organized and dynamic structures as a result of the nematic-isotropic phase transition. These results demonstrate that the LCP-g-OEG micelles have a lot of medical applications as reversibly stimuli-responsive drug carriers.

Direct Cellular Delivery of Exogenous Genetic Material and Protein via Colloidal Nano-Assemblies with Biopolymer

Direct cytosolic delivery of large biomolecules that bypass the endocytic pathways is a promising strategy for therapeutic applications. Recent works have shown that small-molecule, nanoparticle, and polymer-based carriers can be designed for direct cytosolic delivery. It has been shown that the specific surface chemistry of the carrier, nanoscale assembly between the carrier and cargo molecule, good colloidal stability, and low surface charge of the nano-assembly are critical for non-endocytic uptake processes. Here we report a guanidinium-terminated polyaspartic acid micelle for direct cytosolic delivery of protein and DNA. The polymer delivers the protein/DNA directly to the cytosol by forming a nano-assembly, and it is observed that <200 nm size of colloidal assembly with near-zero surface charge is critical for efficient cytosolic delivery. This work shows the importance of size and colloidal property of the nano-assembly for carrier-based cytosolic delivery of large biomolecules.

Phospholipid-Conjugated PEG-b-PCL Copolymers as Precursors of Micellar Vehicles for Amphotericin B

Amphotericin B (AmB) is a widely used antifungal that presents a broad action spectrum and few reports on the development of resistance. However, AmB is highly toxic, causing renal failure in a considerable number of treated patients. Although when AmB is transported via polymer micelles (PMs) as delivery vehicles its nephrotoxicity has been successfully attenuated, this type of nanoparticle has limitations, such as low encapsulation capacity and poor stability in aqueous media. In this research, the effect of modifying polyethyleglicol-block-poly(ε-caprolactone) (PEG-b-PCL) with 1,2-distearoyl-sn-glycero-3-phosphorylethanolamine (DSPE) on the performance of PMs as vehicles for AmB was studied. PEG-b-PCL with two different lengths of a PCL segment was prepared via ring opening polymerisation and modified with DSPE at a post-synthesis stage through amidation. Upon modification with DSPE, a copolymer was self-assembled, thereby producing particles with hydrodynamic diameters below 100 nm and a lower critical micelle concentration than that of the raw copolymers. Likewise, in the presence of DSPE, the loading capacity of AmB increased because of the formed intermolecular interactions, such as hydrogen bonds, which also caused a lower aggregation of this drug. The assessment of in vitro toxicity against red blood cells indicated that the toxicity of AmB decreased upon encapsulation; however, its antifungal action against clinical yeasts was maintained and enhanced, as indicated by a decrease in its minimum inhibitory concentration.

Effects of Processing pH on Emission Intensity of Over-1000 nm Near-Infrared Fluorescence of Dye-Loaded Polymer Micelle with Polystyrene Core

Fluorescence imaging using the over-thousand-nanometer (OTN) near-infrared (NIR) light is an emerging method for an in vivo imaging analysis of deep tissues without physical sectioning. Polymer micelle nanoparticles (PNPs) composed of organic polymers encapsulating an OTN-NIR fluorescent dye, IR-1061, in their hydrophobic core are expected to be biocompatible probes. Because IR-1061 quickly quenches due to the vibration of polar hydroxyl bonding in its surroundings, the influence of hydroxyl ions should be minimized. Herein, we investigated the effect of the hydrogen ion concentration during the preparation process using IR-1061 and an organic polymer, poly(ethylene glycol)-block-polystyrene (PEG-b-PSt), on the emission properties of the obtained OTN-PNPs. The OTN-PNP has a hydrodynamic diameter of 20 - 30 nm and emits 1110-nm fluorescence that is applicable to angiography. The loading efficiency of IR-1061 in the OTN-PNPs increased when prepared in an aqueous solution with a low hydroxyl ion concentration. In this solution (pH 3.0), highly emissive OTN-PNPs was obtained with IR-1061 at lower nominal concentrations. Decreasing the hydroxyl ion concentration during the preparation process yields highly emissive OTN-PNPs, which may improve the in vivo imaging analysis of biological phenomena in deep tissues.

Preparation of mPEG-b-PLA/TM-2 Micelle Lyophilized Products by Mixed Lyoprotectors and Antitumor Effect In Vivo

The objective of this study was to encapsulate the poorly water-soluble drug TM-2 into polymer micelles using mPEG_2k-b-PLA_2.4k to increase its aqueous solubility and improve its therapeutic effect for liver cancer. Furthermore, in order to achieve long-term storage, the micelle solution was successfully freeze-dried. This study theoretically clarified the possibility of enhancing the water solubility of TM-2 using mPEG_2k-b-PLA_2.4k micelles as well as the protective effects of mixed lyoprotectants. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were performed, which showed that the drug has a good affinity with the polymer (χ = 0.489) according to Flory-Huggins theory and that lyoprotectants reduced the crystallinity of PEG in mPEG_2k-b-PLA_2.4k and played a space-protective role in the lyophilization process. In vivo experiments showed that micellization could improve the drug bioavailability and give a high therapeutic effect with a tumor inhibition rate of 84.5% under the tolerated dose.

Therapeutic Effects in a Transient Middle Cerebral Artery Occlusion Rat Model by Nose-To-Brain Delivery of Anti-TNF-Alpha siRNA with Cell-Penetrating Peptide-Modified Polymer Micelles

We previously reported that siRNA delivery to the brain is improved by the nose-to-brain delivery route and by conjugation with polyethylene glycol-polycaprolactone (PEG-PCL) polymer micelles and the cell-penetrating peptide, Tat (PEG-PCL-Tat). In this study, we evaluated the nose-to-brain delivery of siRNA targeting TNF-α (siTNF-α) conjugated with PEG-PCL-Tat to investigate its therapeutic effects on a transient middle cerebral artery occlusion (t-MCAO) rat model of cerebral ischemia-reperfusion injury. Intranasal treatment was provided 30 min after infarction induced via suturing. Two hours after infarction induction, the suture was removed, and blood flow was released. At 22 h post-reperfusion, we assessed the infarcted area, TNF-α production, and neurological score to determine the therapeutic effects. The infarcted area was observed over a wide range in the untreated group, whereas shrinkage of the infarcted area was observed in rats subjected to intranasal administration of siTNF-α with PEG-PCL-Tat micelles. Moreover, TNF-α production and neurological score in rats treated by intranasal administration of siTNF-α with PEG-PCL-Tat micelles were significantly lower than those in untreated and naked siTNF-α-treated rats. These results indicate that nose-to-brain delivery of siTNF-α conjugated with PEG-PCL-Tat micelles alleviated the symptoms of cerebral ischemia-reperfusion injury.

Effect of Hydration in Corona Layer on Structural Change of Thermo-Responsive Polymer Micelles

The effect of hydration in corona layer on temperature responsiveness of polymer micelles consisting of poly(N-vinyl pyrrolidone)-block-poly(n-octadecyl acrylate) (PVP-b-PODA) was investigated. Small-angle X-ray scattering and dynamic light scattering showed two-step shape change of PVP-b-PODA micelles around 45 and 65 °C with elevating temperature, although only one-step shape change was observed at 45 °C in cooling process. In the first step, shape of PVP-b-PODA micelles was changed from disk to ellipsoidal oblate at the melting temperature (T_m) of PODA, although similar micelles consisting of another amphiphilic block copolymers containing PODA simply changed from disk to sphere at the T_m with elevating temperature. PVP-b-PODA micelles changed to spherical shape above 65 °C. Two-dimensional (2D) ¹H-NMR showed the PVP chains were perfectly dehydrated above 65 °C. Therefore, it was suggested that the appearance of ellipsoidal shape between T_m of PODA and 65 °C was caused owing to shape memory effect of pseudo network of corona layer due to robust hydration of PVP chains.

[Development of Noninvasive Drug Delivery Systems to the Brain for the Treatment of Brain/Central Nervous System Diseases]

　In general, the blood-brain barrier (BBB) poses a major challenge to drug development efforts targeting brain/central nervous system (CNS) diseases, since it limits the distribution of systemically administered therapeutics to the brain/ CNS. Therefore, the development of effective strategies for enhancing drug delivery to the brain has been a topic of great interest in both the clinical and pharmaceutical fields. Intranasal administration has been noted as a method for noninvasive delivery of a drug to the brain/CNS by bypassing the BBB via the "nose-to-brain" route. This nose-to-brain delivery system has the potential to be highly versatile, and a combination of this system with new drugs and siRNA shows promise in the treatment of CNS diseases. Cell-penetrating Tat peptide-modified block copolymer micelles have the potential for improving mucosal permeability and nose-to-brain transport efficiency. In addition, nano-sized drug carriers can improve nose-to-brain delivery through their ability to increase the stability of encapsulated drugs against biological degradation in the nasal cavity and brain/CNS. In this review, we introduce the assessment of and mechanisms for delivery to the brain after intranasal drug/siRNA administration with our cell-penetrating peptide-modified nano-sized polymer micelles. Our findings show that the use of polymer micelles with surface modification by cell-penetrating peptides for intranasal administration enables the noninvasive delivery of therapeutic agents to the brain/CNS by increasing the nose-to-brain transfer of the drug or siRNA administered from the nasal cavity.

Preparation of Water-soluble Polyion Complex (PIC) Micelles Covered with Amphoteric Random Copolymer Shells with Pendant Sulfonate and Quaternary Amino Groups

An amphoteric random copolymer (P(SA)91) composed of anionic sodium 2-acrylamido-2-methylpropanesulfonate (AMPS, S) and cationic 3-acrylamidopropyl trimethylammonium chloride (APTAC, A) was prepared via reversible addition-fragmentation chain transfer (RAFT) radical polymerization. The subscripts in the abbreviations indicate the degree of polymerization (DP). Furthermore, AMPS and APTAC were polymerized using a P(SA)91 macro-chain transfer agent to prepare an anionic diblock copolymer (P(SA)91S67) and a cationic diblock copolymer (P(SA)91A88), respectively. The DP was estimated from quantitative 13C NMR measurements. A stoichiometrically charge neutralized mixture of the aqueous P(SA)91S67 and P(SA)91A88 formed water-soluble polyion complex (PIC) micelles comprising PIC cores and amphoteric random copolymer shells. The PIC micelles were in a dynamic equilibrium state between PIC micelles and charge neutralized small aggregates composed of a P(SA)91S67/P(SA)91A88 pair. Interactions between PIC micelles and fetal bovine serum (FBS) in phosphate buffered saline (PBS) were evaluated by changing the hydrodynamic radius (Rh) and light scattering intensity (LSI). Increases in Rh and LSI were not observed for the mixture of PIC micelles and FBS in PBS for one day. This observation suggests that there is no interaction between PIC micelles and proteins, because the PIC micelle surfaces were covered with amphoteric random copolymer shells. However, with increasing time, the diblock copolymer chains that were dissociated from PIC micelles interacted with proteins.

Elucidation of Spatial Distribution of Hydrophobic Aromatic Compounds Encapsulated in Polymer Micelles by Anomalous Small-Angle X-ray Scattering

Spatial distribution of bromobenzene (BrBz) and 4-bromophenol (BrPh) as hydrophobic aromatic compounds incorporated in polymer micelles with vesicular structure consisting of poly(ethylene glycol)-b-poly(tert-butyl methacrylate) (PEG-b-PtBMA) in aqueous solution is investigated by anomalous small-angle X-ray scattering (ASAXS) analyses near Br K edge. Small-angle X-ray scattering (SAXS) intensities from PEG-b-PtBMA micelles containing BrBz and BrPh were decreased as the energy of incident X-ray approached to Br K edge corresponding to the energy dependence of anomalous scattering factor of Br. The analysis for the energy dependence of SAXS profiles from the PEG-b-PtBMA micelles containing BrBz revealed that BrBz molecules were located in hydrophobic layer of PEG-b-PtBMA micelles. On the contrary, it was found by ASAXS that BrPh existed not only in the hydrophobic layer but also in the shell layer. Since ASAXS analysis successfully accomplished to visualize the spatial distribution of hydrophobic molecules in polymer micelles, it should be expected to be a powerful tool for characterization of drug delivery vehicles.

Vitamin C-Conjugated Nanoparticle Protects Cells from Oxidative Stress at Low Doses but Induces Oxidative Stress and Cell Death at High Doses

Although the antioxidant property of vitamin C is well-known for protecting cells from oxidative stress, a recent study shows that it can also generate oxidative stress under a high intracellular concentration and induce cell death. However, poor chemical stability and low biological concentration (micromolar) of vitamin C restrict its function primarily as an antioxidant. Here, we report two different nanoparticle forms of vitamin C with its intact chemical stability, glucose-responsive release from nanoparticle, and efficient cell delivery in micro to millimolar concentrations. Nanoparticles are composed of silica-coated Au nanoparticles or lipophilic polyaspartic acid-based polymer micelles which are conjugated with vitamin C via phenylboronic acid. Surface chemistry of nanoparticles is optimized for an efficient cellular interaction/uptake and for cell delivery of vitamin C. We found that vitamin C protects cells from oxidative stress at micromolar concentrations, but at millimolar concentrations, it induces cell death by generating oxidative stress. In particular, high-dose vitamin C produces H₂O₂, disrupts the cellular redox balance, and induces cell death. This study highlights the concentration-dependent biological performance of vitamin C and the requirement of a high-dose cell delivery approach for enhanced therapeutic benefit.

Surface Active to Non-Surface Active Transition and Micellization Behaviour of Zwitterionic Amphiphilic Diblock Copolymers: Hydrophobicity and Salt Dependency

We have synthesized a range of zwitterionic amphiphilic diblock copolymers with the same hydrophilic block (carboxybetaine) but with different hydrophobic blocks (n-butylmethacrylate (n-BMA) or 2-ethylhexylacrylate (EHA)) by the reversible addition⁻fragmentation chain transfer (RAFT) polymerization method. Herein, we systematically examined the role of hydrophobicity and salt concentration dependency of surface activity and micellization behaviour of block copolymer. Transition from surface active to non-surface active occurred with increasing hydrophobicity of the hydrophobic block of block copolymer (i.e., replacing P(n-BMA) by PEHA). Foam formation of block copolymer slightly decreased with the similar variation of the hydrophobic block of block copolymer. Block copolymer with higher hydrophobicity preferred micelle formation rather than adsorption at the air⁻water interface. Dynamic light scattering studies showed that block copolymer having P(n-BMA) produced near-monodisperse micelles, whereas block copolymer composed of PEHA produced polydisperse micelles. Zimm plot results revealed that the value of the second virial coefficient (A₂) changed from positive to negative when the hydrophobic block of block copolymer was changed from P(n-BMA) to PEHA. This indicates that the solubility of block copolymer having P(n-BMA) in water may be higher than that of block copolymer having PEHA in water. Unlike ionic amphiphilic block copolymer micelles, the micellar shape of zwitterionic amphiphilic block copolymer micelles is not affected by addition of salt, with a value of packing parameters of block copolymer micelles of less than 0.3.

Cell microenvironment-controlled antitumor drug releasing-nanomicelles for GLUT1-targeting hepatocellular carcinoma therapy

In clinical therapy, the poor prognosis of hepatocellular carcinoma (HCC) is mainly attributed to the failure of chemotherapeutical agents to accumulate in tumor as well as their serious systemic toxicity. In this work, we developed actively tumor-targeting trilayer micelles with microenvironment-sensitive cross-links as a novel nanocarrier for HCC therapy. These micelles comprised biodegradable PEG-pLys-pPhe polymers, in which pLys could react with a disulfide-containing agent to form redox-responsive cross-links. In vitro drug release and pharmacokinetics studies showed that these cross-links were stable in physiological condition whereas cleaved once internalized into cells due to the high level of glutathione, resulting in facilitated intracellular doxorubicin release. In addition, dehydroascorbic acid (DHAA) was decorated on the surface of micelles for specific recognition of tumor cells via GLUT1, a member of glucose transporter family overexpressed on hepatocarcinoma cells. Moreover, DHAA exhibited a "one-way" continuous accumulation within tumor cells. Cellular uptake and in vivo imaging studies proved that these micelles had remarkable targeting property toward hepatocarcinoma cells and tumor. Enhanced anti-HCC efficacy of the micelles was also confirmed both in vitro and in vivo. Therefore, this micellar system may be a potential platform of chemotherapeutics delivery for HCC therapy.

Synthesis of amphiphilic star block copolymers and their evaluation as transdermal carriers

Amphiphilic star polymers offer substantial promise for a range of drug delivery applications owing to their ability to encapsulate guest molecules. One appealing but underexplored application is transdermal drug delivery using star block copolymer reverse micelles as an alternative to the more common oral and intravenous routes. We prepared 6- and 12-arm amphiphilic star copolymers via atom transfer radical polymerization (ATRP) of sequential blocks of polar oligo (ethylene glycol)methacrylate and nonpolar lauryl methacrylate from brominated dendritic macroinitiators based on 2,2-bis(hydroxymethyl) propionic acid. These star block copolymers demonstrate the ability to encapsulate polar dyes such as rhodamine B and FITC-BSA in nonpolar media via UV/vis spectroscopic studies and exhibit substantially improved encapsulation efficiencies, relative to self-assembled "1-arm" linear block copolymer analogs. Furthermore, their transdermal carrier capabilities were demonstrated in multiple dye diffusion studies using porcine skin, verifying penetration of the carriers into the stratum corneum.

MAD (multiagent delivery) nanolayer: delivering multiple therapeutics from hierarchically assembled surface coatings

We present hydrolytically degradable polymeric multilayer films that can codeliver multiple therapeutics of differing chemical characteristics (charged biomacromolecules and neutral hydrophobic small molecules) from a surface. This multiagent-delivery (MAD) nanolayer system integrates the hydrolytically degradable poly(beta-amino ester) as a structural component to control the degradation of the multilayers to release active therapeutic macromolecules as well as hydrophobic drugs imbedded within amphiphilic block copolymer micellar carriers within layer-by-layer (LbL) films, which would otherwise be difficult to include within the multilayers. By varying the anionic therapeutic agents (heparin and dextran sulfate) within the multilayer, we examine how different structural components can be used to control the release kinetics of multiple therapeutics from MAD nanolayers. Controlled release profiles and the in vitro efficacy of the MAD nanolayers in suppressing the growth of human smooth muscle cell lines were evaluated. The dual delivery of a charged macromolecular heparin and a small hydrophobic drug, paclitaxel, is found to be synergistic and beneficial toward effective therapeutic activity. Furthermore, we compared the classical dipping method that we employed here with an automated spray-LbL technique. Spray-LbL significantly facilitates film processing time while preserving the characteristic release profiles of the MAD nanolayers. With the highly versatile and tunable nature of LbL assembly, we anticipate that MAD nanolayers can provide a unique platform for delivering multiple therapeutics from macromolecules to small molecules with distinct release profiles for applications in biological and biomedical surface coatings.