Physical stimuli-responsive polymeric micelles for anti-cancer drug delivery

In Situ Polymorphic Alteration of Filler Structures for Biomimetic Mechanically Adaptive Elastomer Nanocomposites

A mechanically adaptable elastomer composite is prepared with reversible soft-stiff properties that can be easily controlled. By the exploitation of different morphological structures of calcium sulfate, which acts as the active filler in a soft elastomer matrix, the magnitude of filler reinforcement can be reversibly altered, which will be reflected in changes of the final stiffness of the material. The higher stiffness, in other words, the higher modulus of the composites, is realized by the in situ development of fine nanostructured calcium sulfate dihydrate crystals, which are formed during exposure to water and, further, these highly reinforcing crystals can be transformed to a nonreinforcing hemihydrate mesocrystalline structure by simply heating the system in a controlled way. The Young's modulus of the developed material can be reversibly altered from ∼6 to ∼17 MPa, and the dynamic stiffness (storage modulus at room temperature and 10 Hz frequency) alters its value in the order of 1000%. As the transformation is related to the presence of water molecules in the crystallites, a hydrophilic elastomer matrix was selected, which is a blend of two hydrophilic polymers, namely, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer and a terpolymer of ethylene oxide-propylene oxide-allyl glycidyl ether. For the first time, this method also provides a route to regulate the morphology and structure of calcium sulfate nanocrystals in a confined ambient of cross-linked polymer chains.

Nanoparticles and Controlled Delivery for Bioactive Compounds: Outlining Challenges for New "Smart-Foods" for Health

Nanotechnology is a field of research that has been stressed as a very valuable approach for the prevention and treatment of different human health disorders. This has been stressed as a delivery system for the therapeutic fight against an array of pathophysiological situations. Actually, industry has applied this technology in the search for new oral delivery alternatives obtained upon the modification of the solubility properties of bioactive compounds. Significant works have been made in the last years for testing the input that nanomaterials and nanoparticles provide for an array of pathophysiological situations. In this frame, this review addresses general questions concerning the extent to which nanoparticles offer alternatives that improve therapeutic value, while avoid toxicity, by releasing bioactive compounds specifically to target tissues affected by specific chemical and pathophysiological settings. In this regard, to date, the contribution of nanoparticles to protect encapsulated bioactive compounds from degradation as a result of gastrointestinal digestion and cellular metabolism, to enable their release in a controlled manner, enhancing biodistribution of bioactive compounds, and to allow them to target those tissues affected by biological disturbances has been demonstrated.

Cure of tuberculosis using nanotechnology: An overview

Mycobacterium tuberculosis is the causative agent of tuberculosis (TB), a major health issue of the present era. The bacterium inhabits the host macrophage and other immune cells where it modulates the lysosome trafficking protein, hinders the formation of phagolysosome, and blocks the TNF receptor-dependent apoptosis of host macrophage/monocytes. Other limitations such as resistance to and low bioavailability and bio-distribution of conventional drugs aid to their high virulence and human mortality. This review highlights the use of nanotechnology-based approaches for drug formulation and delivery which could open new avenues to limit the pathogenicity of tuberculosis. Moreover phytochemicals, such as alkaloids, phenols, saponins, steroids, tannins, and terpenoids, extracted from terrestrial plants and mangroves seem promising against M. tuberculosis through different molecular mechanisms. Further understanding of the genomics and proteomics of this pathogenic microbe could also help overcome various research gaps in the path of developing a suitable therapy against tuberculosis.

Self-Assembled pH-Responsive Polymeric Micelles for Highly Efficient, Noncytotoxic Delivery of Doxorubicin Chemotherapy To Inhibit Macrophage Activation: In Vitro Investigation

Self-assembled pH-responsive polymeric micelles, a combination of hydrophilic poly(ethylene glycol) segments and hydrogen bonding interactions within a biocompatible polyurethane substrate, can spontaneously self-assemble into highly controlled, nanosized micelles in aqueous solution. These newly developed micelles exhibit excellent pH-responsive behavior and biocompatibility, highly controlled drug (doxorubicin; DOX) release behavior, and high drug encapsulation stability in different aqueous environments, making the micelles highly attractive potential candidates for safer, more effective drug delivery in applications such as cancer chemotherapy. In addition, in vitro cell studies revealed the drug-loaded micelles possessed excellent drug entrapment stability and low cytotoxicity toward macrophages under normal physiological conditions (pH 7.4, 37 °C). When the pH of the culture media was reduced to 6.0 to mimic the acidic tumor microenvironment, the drug-loaded micelles triggered rapid release of DOX within the cells, which induced potent antiproliferative and cytotoxic effects in vitro. Importantly, fluorescent imaging and flow cytometric analyses confirmed the DOX-loaded micelles were efficiently delivered into the cytoplasm of the cells via endocytosis and then subsequently gradually translocated into the nucleus. Therefore, these multifunctional micelles could serve as delivery vehicles for precise, effective, controlled drug release to prevent accumulation and activation of tumor-promoting tumor-associated macrophages in cancer tissues. Thus, this unique system may offer a potential route toward the practical realization of next-generation pH-responsive therapeutic delivery systems.

Effects of processing parameters on the properties of amphiphilic block copolymer micelles prepared by supercritical carbon dioxide evaporation method

The operation parameters for the supercritical carbon dioxide (ScCO2) evaporation method greatly affect the properties of the prepared drug-loaded micelles. In this study, the effects of those key parameters on the drug-loading content (LC) and drug entrapment efficiency (EE) are discussed. It is observed that EE and LC of the micelles are slightly increased with the enhancing temperature and the copolymer molecular ratio of hydrophilic/hydrophobic segment, while decreased with the enhancing ScCO2 evaporation rate. The pressure and volume ratio of ScCO2 to H2O are observed the optimum condition. In addition, the verification experiment is carried out under the obtained optimizing parameters. The prepared micelles exhibit relatively regular spherical shape and narrow size distribution with the EE and LC value of 70.7% and 14.1%, respectively.

Supramolecular Chemotherapy: Carboxylated Pillar[6]arene for Decreasing Cytotoxicity of Oxaliplatin to Normal Cells and Improving Its Anticancer Bioactivity Against Colorectal Cancer

We have successfully demonstrated that the host-guest complex of carboxylated pillar[6]arene with oxaliplatin (OxPt) exhibits low cytotoxicity toward normal cells and displays higher anticancer bioactivity against colorectal cancer cells than OxPt itself. Owing to higher binding affinity of carboxylated pillar[6]arene with spermine (SPM) than that with OxPt, the encapsulated OxPt can be thoroughly released from its host-guest complex by the competitive replacement with SPM. This supramolecular chemotherapy works well both in vitro and in vivo for SPM-overexpressed cancers, such as colorectal cancer. Compared to OxPt itself, the anticancer bioactivity of this host-guest complex is further improved by about 20%. Such an improvement results from the combined effect of controlled release of OxPt from its host-guest complex and simultaneous consumption of SPM by carboxylated pillar[6]arene. It is anticipated that this supramolecular strategy may be extended to other clinical anticancer drugs for decreasing their severe side effects and improving their anticancer bioactivity, thus enriching the realm of supramolecular chemotherapy.

Stimulus-responsive liposomes as smart nanoplatforms for drug delivery applications

Liposomes are known to be promising nanoparticles (NPs) for drug delivery applications. Among different types of self-assembled NPs, liposomes stand out for their non-toxic nature, and their possession of dual hydrophilic-hydrophobic domains. Advantages of liposomes include the ability to solubilize hydrophobic drugs, the ability to incorporate different hydrophilic and lipophilic drugs at the same time, lessening the exposure of host organs to potentially toxic drugs and allowing modification of the surface by a variety of different chemical groups. This modification of the surface, or of the individual constituents, may be used to achieve two important goals. Firstly, ligands for active targeting can be attached that are recognized by cognate receptors over-expressed on the target cells of tissues. Secondly, modification can be used to impart a stimulus-responsive or "smart" character to the liposomes, whereby the cargo is released on demand only when certain internal stimuli (pH, reducing agents, specific enzymes) or external stimuli (light, magnetic field or ultrasound) are present. Here, we review the field of smart liposomes for drug delivery applications.

Systematic design and application of unimolecular star-like block copolymer micelles: a coarse-grained simulation study

Unimolecular polymeric micelles have several features, such as thermodynamic stability, small particle size, biocompatibility, and the ability to internalize hydrophobic molecules. These micelles have recently attracted significant attention in various applications, such as nano-reactors, catalysis, and drug delivery. However, few attempts have explored the formation mechanisms and conditions of unimolecular micelles due to limited experimental techniques. In this study, a unimolecular micelle system formed from β-cyclodextrin-graft-{poly(lactide)-block-poly(2-(dimethylamino) ethyl multimethacrylate)-block-poly[oligo (2-ethyl-2-oxazoline) methacrylate]} β-CD-g-(PLA-b-PDMAEMA-b-PEtOxMA) star-like block copolymers in aqueous media was investigated by dissipative particle dynamics (DPD) to explore the formation process of unimolecular micelles. The simulation results showed that using longer hydrophobic or pH-sensitive chains, shorter hydrophilic backbones, smaller hydrophilic side chain grafting density, and fewer polymer arms resulted in micellar aggregation. Furthermore, this unimolecular polymeric micelle could be used for encapsulating gold nanoparticles, whose mesoscopic structure was also explored. The gold nanoparticles tended to distribute in the middle layer formed by PDMAEMA, and the unimolecular micelles were capable of impeding gold nanoparticle aggregation. This study could help understand the formation mechanism of unimolecular micelles formed from star-like block copolymers in dilute solutions and offer a theoretical guide to the design and preparation of promising unimolecular polymeric micelles with targeting properties.

Optimization of Weight Ratio for DSPE-PEG/TPGS Hybrid Micelles to Improve Drug Retention and Tumor Penetration

PURPOSE

To enhance therapeutic efficacy and prevent phlebitis caused by Asulacrine (ASL) precipitation post intravenous injection, ASL-loaded hybrid micelles with size below 40 nm were developed to improve drug retention and tumor penetration.

METHODS

ASL-micelles were prepared using different weight ratios of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-polyethyleneglycol-2000 (DSPE-PEG₂₀₀₀) and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) polymers. Stability of micelles was optimized in terms of critical micelle concentration (CMC) and drug release properties. The encapsulation efficiency (EE) and drug loading were determined using an established dialysis-mathematic fitting method. Multicellular spheroids (MCTS) penetration and cytotoxicity were investigated on MCF-7 cell line. Pharmacokinetics of ASL-micelles was evaluated in rats with ASL-solution as control.

RESULTS

The ASL-micelles prepared with DSPE-PEG₂₀₀₀ and TPGS (1:1, w/w) exhibited small size (~18.5 nm), higher EE (~94.12%), better sustained in vitro drug release with lower CMC which may be ascribed to the interaction between drug and carriers. Compared to free ASL, ASL-micelles showed better MCTS penetration capacity and more potent cytotoxicity. Pharmacokinetic studies demonstrated that the half-life and AUC values of ASL-micelles were approximately 1.37-fold and 3.49-fold greater than that of free ASL.

CONCLUSIONS

The optimized DSPE-PEG₂₀₀₀/TPGS micelles could serve as a promising vehicle to improve drug retention and penetration in tumor.

A core/shell stabilized polysaccharide-based nanoparticle with intracellular environment-sensitive drug delivery for breast cancer therapy

In this work, we developed a novel core/shell chitosan (Cs)/hyaluronan (HA)-based hybrid nanoparticle, i.e. SNX@Cs-SNX/cHA, with good stability in the bloodstream and intracellular environment-sensitive drug delivery for breast cancer therapy.

A pH-sensitive guar gum-grafted-lysine-β-cyclodextrin drug carrier for the controlled release of 5-flourouracil into cancer cells

The physiological environment is a crucial factor in biomedical systems, which can be regulated with relative ease both in vitro and in vivo.

Phase-shifted paclitaxel-loaded multifunctional contrast agent for US/MR imaging and synergistic hyperthermal/chemotherapy of metastasis in lymph nodes

The existing approaches used to detect a tumor-induced sentinel lymph node and treat metastasis have limitations. In this study, by encapsulating perfluoropentane (PFP), magnetic iron oxide nanoparticles (Fe₃O₄) and the chemotherapy drug paclitaxel (PTX), we fabricated novel polymer nanoparticles (NPNs) that can effectively absorb heat after irradiation by near-infrared irradiation (NIR), thereby synergistically enhancing tumor therapy via a phase-shift thermoelastic expansion effect. These NPNs can be used for dual-modal ultrasound (US) and magnetic resonance (MR) imaging and to treat metastasis in lymph nodes under NIR irradiation-triggered drug delivery. The enhancement of US/MR imaging proved effective in vitro and in vivo, and NIR irradiation proved valid, promoting PTX release at the target site. A lower proliferation index and density and a higher tumor cell apoptotic index in the histopathology results confirmed the effectiveness of NPN chemotherapy for lymph nodes.

We fabricated novel polymer nanoparticles that can effectively absorb heat after irradiation by NIR irradiation, thereby synergistically enhancing tumor therapy via a phase-shift thermoelastic expansion effect.

Release of Solubilizate from Micelle upon Core Freezing

By combining NMR (yielding ¹H chemical shift, spin relaxation, and self-diffusion data) and small-angle X-ray scattering experiments, we investigate the complex temperature dependence of the molecular and aggregate states in aqueous solutions of the surfactant [CH₃(CH₂)₁₇(OCH₂CH₂)₂₀OH], abbreviated as C18E20, and hexamethyldisiloxane, HMDSO. The latter molecule serves as a model for hydrophobic solubilizates. Previously, the pure micellar solution was demonstrated to exhibit core freezing at approximately 7-8 °C. At room temperature, we find that HMDSO solubilizes at a volume fraction of approximately 10% in the core of the C18E20 micelles, which consists of molten and thereby highly mobile alkyl chains. Upon lowering the temperature, core freezing is found, just like in pure micelles, but at a temperature shifted significantly to 3 °C. The frozen cores contain immobile alkyl chains and exhibit a higher density but are essentially devoid (volume fraction below 1%) of the solubilizate. The latter molecules are released, first gradually and then rather steeply, from the core in the temperature range that is roughly delimited by the two core freezing temperatures, one for pure micelles and one for micelles with solubilizates. The release behavior of systems with different initial HMDSO loading follows the same master curve. This feature is rationalized in terms of loading capacity being strongly temperature dependent: upon lowering the temperature, release commences once the loading capacity descends below the actual solubilizate content. The sharp release curves and the actual release mechanism with its molecular features shown in rich detail have some bearing on a diverse class of possible applications.

Nanotechnologies in Pancreatic Cancer Therapy

Pancreatic cancer has been classified as a cancer of unmet need. After diagnosis the patient prognosis is dismal with few surviving over 5 years. Treatment regimes are highly patient variable and often the patients are too sick to undergo surgical resection or chemotherapy. These chemotherapies are not effective often because patients are diagnosed at late stages and tumour metastasis has occurred. Nanotechnology can be used in order to formulate potent anticancer agents to improve their physicochemical properties such as poor aqueous solubility or prolong circulation times after administration resulting in improved efficacy. Studies have reported the use of nanotechnologies to improve the efficacy of gemcitabine (the current first line treatment) as well as investigating the potential of using other drug molecules which have previously shown promise but were unable to be utilised due to the inability to administer through appropriate routes-often related to solubility. Of the nanotechnologies reported, many can offer site specific targeting to the site of action as well as a plethora of other multifunctional properties such as image guidance and controlled release. This review focuses on the use of the major nanotechnologies both under pre-clinical development and those which have recently been approved for use in pancreatic cancer therapy.

Polymeric micelles: Basic research to clinical practice

Rapidly developing polymeric micelles as potential targeting carriers has intensified the need for better understanding of the underlying principles related to the selection of suitable delivery materials for designing, characterizing, drug loading, improving stability, targetability, biosafety and efficacy. The emergence of advanced analytical tools such as fluorescence resonance energy transfer and dissipative particle dynamics has identified new dimensions of these nanostructures and their behavior in much greater details. This review summarizes recent efforts in the development of polymeric micelles with respect to their architecture, formulation strategy and targeting possibilities along with their preclinical and clinical aspects. Literature of the past decade is discussed critically with special reference to the chemistry involved in the formation and clinical applications of these versatile materials. Thus, our main objective is to provide a timely update on the current status of polymeric micelles highlighting their applications and the important parameters that have led to successful delivery of drugs to the site of action.

In vitro microfluidic models of tumor microenvironment to screen transport of drugs and nanoparticles

Advances in nanotechnology have enabled numerous types of nanoparticles (NPs) to improve drug delivery to tumors. While many NP systems have been proposed, their clinical translation has been less than anticipated primarily due to failure of current preclinical evaluation techniques to adequately model the complex interactions between the NP and physiological barriers of tumor microenvironment. This review focuses on microfluidic tumor models for characterization of delivery efficacy and toxicity of cancer nanomedicine. Microfluidics offer significant advantages over traditional macroscale cell cultures by enabling recapitulation of tumor microenvironment through precise control of physiological cues such as hydrostatic pressure, shear stress, oxygen, and nutrient gradients. Microfluidic systems have recently started to be adapted for screening of drugs and NPs under physiologically relevant settings. So far the two primary application areas of microfluidics in this area have been high-throughput screening using traditional culture settings such as single cells or multicellular tumor spheroids, and mimicry of tumor microenvironment for study of cancer-related cell-cell and cell-matrix interactions. These microfluidic technologies are also useful in modeling specific steps in NP delivery to tumor and characterize NP transport properties and outcomes by systematic variation of physiological conditions. Ultimately, it will be possible to design drug-screening platforms uniquely tailored for individual patient physiology using microfluidics. These in vitro models can contribute to development of precision medicine by enabling rapid and patient-specific evaluation of cancer nanomedicine. WIREs Nanomed Nanobiotechnol 2017, 9:e1460. doi: 10.1002/wnan.1460 For further resources related to this article, please visit the WIREs website.

Ultrasound-triggered PLGA microparticle destruction and degradation for controlled delivery of local cytotoxicity and drug release

In this study, we investigated the low intensity ultrasound (US)-controlled delivery of local cytotoxicity and drug release via induced destruction and degradation of microparticles (MPs) made of poly(lactic-co-glycolic acid) (PLGA). This study was conducted in vitro with potential application towards tumor treatment in conjunction with direct injection. MPs, either loaded with or without doxorubicin (DOX), were prepared using a double-emulsion solvent-evaporation technique. First, the MPs were exposed to US with duty cycle (DC)-modulation. The destruction and degradation of MPs were evaluated using light and scanning electron microscopy. Second, the effects of US-mediated destruction/degradation of MPs on the local cytotoxicity as well as DOX release were evaluated. US-triggered MP destruction/degradation significantly enhanced nearby cell death and DOX release. These affects occurred in proportion to the DC. Our findings indicate that controlled cytotoxicity and DOX release by US could be useful in developing the minimally invasive therapeutic applications for tumor treatment.

Non-invasive strategies for targeting the posterior segment of eye

The safe and effective treatment of eye diseases has been remained a global myth. Several advancements have been done and various drug delivery and treatment techniques have been suggested. The Posterior segment disorders are the leading cause of visual impairments and blindness. Targeting the therapeutic agents to the anterior and posterior segments of the eye has attracted extensive attention from the scientific community. Significant key factors in the success of ocular therapy are the development of safe, effective, economic and non-invasive novel drug delivery systems. These specialized non-invasive ocular drug delivery systems revolutionized the drug delivery strategies by overcoming the limitations, provided targeted delivery to the ocular tissues by avoiding larger doses, and reducing the toxicity encountered by the conventional approaches. These non-invasive systems are fabricated by ingredients encompassing biodegradability, biocompatibility, mucoadhesion, solubility and permeability enhancement and stimuli responsiveness. The variety of routes are utilized to provide minimally invasive drug delivery to the patients without any discomfort and pain. This review is focused on the brief introduction, types, significance, preparation techniques, components and mechanism of drug release of non-invasive systems, including in situ gelling systems, microspheres, iontophoresis, nanoparticles, nanosuspensions and specialized novel emulsions.

Synthesis and Phase Transition of Poly(N-isopropylacrylamide)-Based Thermo-Sensitive Cyclic Brush Polymer

Polymers with advanced topological architectures are promising materials for wide applications due to their structure-generated unique properties different from that of the linear analogues. The elegant integration of stimuli-responsive polymers with such advanced architectures can create novel materials with virtues from both moieties, are thus a hot subject of research for both fundamental and practical investigations. To fabricate cyclic brush polymer-based intelligent materials for biomedical applications, herein, we designed and synthesized thermo-sensitive cyclic brush polymers with poly(N-isopropylacrylamide) (PNIPAAm) brushes by controlled living radical polymerization using cyclic multimacroinitiator. The thermo-induced phase transition behaviors of the resultant cyclic brush polymers with different compositions were investigated in detail by temperature-dependent optical transmittance measurements, and compared with the properties of bottlebrush and linear counterparts. Interestingly, the cloud point transition temperature (Tcp) of cyclic brush PNIPAAm could be regulated by the chain length of PNIPAAm brush. Although the bottlebrush polymers with the same composition exhibited similarly structurally dependent Tcps behaviors to the cyclic brush polymers, the cyclic brush PNIPAAm did show higher critical aggregation concentration (CAC) and enhanced stability against dilution than the bottlebrush counterpart. The readily tailorable Tcps together with the ability to form highly stable nanoparticles makes thermo-sensitive cyclic brush PNIPAAm a promising candidate for controlled drug delivery.

Nanomaterials for the Capture and Therapeutic Targeting of Circulating Tumor Cells

Circulating tumor cells are a hallmark of cancer metastasis which accounts for approximately 90% of all cancer-related deaths. Their detection and characterization have significant implications in cancer biology and clinical practice. However, CTCs are rare cells and consist of heterogeneous subpopulations, requiring highly sensitive and specific techniques to identify and isolate them with high efficiency. Nanomaterials, with unique structural and functional properties, have shown strong promise to meet the challenging demands. In this review, we discuss CTC capture and therapeutic targeting, emphasizing the significance of the nanomaterials being used for this purpose. The next generation of therapy for metastatic cancer may well involve capturing and even directly neutralizing CTCs using nanomaterials.

Acoustic Sensing and Ultrasonic Drug Delivery in Multimodal Theranostic Capsule Endoscopy

Video capsule endoscopy (VCE) is now a clinically accepted diagnostic modality in which miniaturized technology, an on-board power supply and wireless telemetry stand as technological foundations for other capsule endoscopy (CE) devices. However, VCE does not provide therapeutic functionality, and research towards therapeutic CE (TCE) has been limited. In this paper, a route towards viable TCE is proposed, based on multiple CE devices including important acoustic sensing and drug delivery components. In this approach, an initial multimodal diagnostic device with high-frequency quantitative microultrasound that complements video imaging allows surface and subsurface visualization and computer-assisted diagnosis. Using focused ultrasound (US) to mark sites of pathology with exogenous fluorescent agents permits follow-up with another device to provide therapy. This is based on an US-mediated targeted drug delivery system with fluorescence imaging guidance. An additional device may then be utilized for treatment verification and monitoring, exploiting the minimally invasive nature of CE. While such a theranostic patient pathway for gastrointestinal treatment is presently incomplete, the description in this paper of previous research and work under way to realize further components for the proposed pathway suggests it is feasible and provides a framework around which to structure further work.

Self-assembled amphiphilic core-shell nanocarriers in line with the modern strategies for brain delivery

Disorders of the central nervous system (CNS) represent increasing social and economic problems all over the world which makes the effective transport of drugs to the brain a crucial need. In the last decade, many strategies were introduced to deliver drugs to the brain trying to overcome the challenge of the blood brain barrier (BBB) using both invasive and non-invasive methods. Non-invasive strategy represented in the application of nanocarriers became very common. One of the most hopeful nanoscopic carriers for brain delivery is core-shell nanocarriers or polymeric micelles (PMs). They are more advantageous than other nanocarriers. They offer small size, ease of preparation, ease of sterilization and the possibility of surface modification with various ligands. Hence, the aim of this review is to discuss modern strategies for brain delivery, micelles as a successful delivery system for the brain and how micelles could be modified to act as "magic bullets" for brain delivery.

An ATP-Responsive Codelivery System of Doxorubicin and MiR-34a To Synergistically Inhibit Cell Proliferation and Migration

Establishing stimulus-responsive nanosystems for the codelivery of anticancer drug and oligonucleotide is a promising strategy in cancer treatment owing to the combination of chemotherapy and gene therapy in a synergistic manner. Herein, an ATP aptamer and its cDNA sequence were first hybridized to produce the duplex, into which chemotherapeutic agent doxorubicin (DOX) interacted through the GC-rich motif of duplex, and PEI25K was then employed as a carrier to condense the DOX-loading duplex and miR-34a to construct the ternary nanocomplex PEI/DOX-Duplex/miR-34a. The nanocomplex exhibited a favorable drug release profile through the response to high concentration of ATP in the cytosol. The ATP-responsive delivery system was demonstrated to possess higher antiproliferative effect (cell viability of <40%) than the single cargo delivery, which could be attributed to the synergistic induction of cell apoptosis and cell cycle arrest from DOX and miR-34a. Furthermore, wound healing and Transwell assay elucidated the higher antimigration effect of ternary nanocomplex than DOX-Duplex or miR-34a delivery. Overall, the combinatorial delivery of DOX and miR-34a through an ATP-responsive manner could trigger the rapid release of cargoes in the cytosol and enhance the inhibition of cell proliferation and migration through the synergistic manner of these two components.

K+ -Responsive Block Copolymer Micelles for Targeted Intracellular Drug Delivery

In this work, a novel type of block copolymer micelles with K⁺ -responsive characteristics for targeted intracellular drug delivery is developed. The proposed smart micelles are prepared by self-assembly of poly(ethylene glycol)-b-poly(N-isopropylacry-lamide-co-benzo-18-crown-6-acrylamide) (PEG-b-P(NIPAM-co-B18C6Am)) block copolymers. Prednisolone acetate (PA) is successfully loaded into the micelles as the model drug, with loading content of 4.7 wt%. The PA-loaded micelles display a significantly boosted drug release in simulated intracellular fluid with a high K⁺ concentration of 150 × 10^-3 m, as compared with that in simulated extracellular fluid. Moreover, the in vitro cell experiments indicate that the fluorescent molecules encapsulated in the micelles can be delivered and specifically released inside the HSC-T6 and HepG2 cells responding to the increase of K⁺ concentration in intracellular compartments, which confirms the successful endocytosis and efficient K⁺ -induced intracellular release. Such K⁺ -responsive block copolymer micelles are highly potential as new-generation of smart nanocarriers for targeted intracellular delivery of drugs.

α-Amylase- and Redox-Responsive Nanoparticles for Tumor-Targeted Drug Delivery

Paclitaxel (PTX) is an effective antineoplastic agent and shows potent antitumor activity against a wide spectrum of cancers. Yet, the wide clinical use of PTX is limited by its poor aqueous solubility and the side effects associated with its current therapeutic formulation. To tackle these obstacles, we report, for the first time, α-amylase- and redox-responsive nanoparticles based on hydroxyethyl starch (HES) for the tumor-targeted delivery of PTX. PTX is conjugated onto HES by a redox-sensitive disulfide bond to form HES-SS-PTX, which was confirmed by results from NMR, high-performance liquid chromatography-mass spectrometry, and Fourier transform infrared spectrometry. The HES-SS-PTX conjugates assemble into stable and monodispersed nanoparticles (NPs), as characterized with Dynamic light scattering, transmission electron microscopy, and atomic force microscopy. In blood, α-amylase will degrade the HES shell and thus decrease the size of the HES-SS-PTX NPs, facilitating NP extravasation and penetration into the tumor. A pharmacokinetic study demonstrated that the HES-SS-PTX NPs have a longer half-life than that of the commercial PTX formulation (Taxol). As a consequence, HES-SS-PTX NPs accumulate more in the tumor compared with the extent of Taxol, as shown in an in vivo imaging study. Under reductive conditions, the HES-SS-PTX NPs could disassemble quickly as evidenced by their triggered collapse, burst drug release, and enhanced cytotoxicity against 4T1 tumor cells in the presence of a reducing agent. Collectively, the HES-SS-PTX NPs show improved in vivo antitumor efficacy (63.6 vs 52.4%) and reduced toxicity in 4T1 tumor-bearing mice compared with those of Taxol. These results highlight the advantages of HES-based α-amylase- and redox-responsive NPs, showing their great clinical translation potential for cancer chemotherapy.

Synthesis, characterisation and phase transition behaviour of temperature-responsive physically crosslinked poly (N-vinylcaprolactam) based polymers for biomedical applications

Poly (N-vinylcaprolactam) (PNVCL) is a polymer which offers superior characteristics for various potential medical device applications. In particular it offers unique thermoresponsive capabilities, which fulfils the material technology constraints required in targeted drug delivery applications. PNVCL phase transitions can be tailored in order to suit the requirements of current and next generation devices, by modifying the contents with regard to the material composition and aqueous polymer concentration. In this study, physically crosslinked Poly (N-vinylcaprolactam)-Vinyl acetate (PNVCL-VAc) copolymers were prepared by photopolymerisation. The structure of the polymers was established by Fourier transform infrared spectroscopy, nuclear magnetic resonance and gel permeation chromatography. The polymers were further characterised using differential scanning calorimetry and swelling studies. Determination of the LCST of the polymers in aqueous solution was achieved by employing four techniques; cloud point, UV-spectrometry, differential scanning calorimetry and rheometry. Sol-gel transition was established using tube inversion method and rheological analysis. This study was conducted to determine the characteristics of PNVCL with the addition of VAc, and to establish the effects on the phase transition. The PNVCL based polymers exhibited a decrease in the LCST as the composition of VAc increased. Sol-gel transition could be controlled by altering the monomeric feed ratio and polymer concentration in aqueous milieu. Importantly all copolymers (10wt% in solution) underwent gelation between 33.6 and 35.9°C, and based on this and the other materials properties recorded in this study, these novel copolymers have potential for use as injectable in situ forming drug delivery systems for targeted drug delivery.

Nonradiation Cellular Thermometry Based on Interfacial Thermally Induced Phase Transformation in Polymer Coating of Optical Microfiber

A nonradiation approach based on thermoresponsive polymer coated silica microfibers has been developed. A highly thermoresponsive and biocompatible poly(N-isopropylacrylamide) (pNIPAM) was surface functionlized to conjugate to the tapered silica microfiber with waist diameter of 7.5 μm. The interfacial phase transtition of coating triggered by the lower critical solution temperature (LCST) causes a drastic molecular morphological change in the body temperature range of 35-42 °C. This surface morphological change strongly modulates optical path difference between the higher order and the fundamental mode propagating in the microfiber because of the evanescent-field interaction and, therefore, shifts the intermodal interference fringe. Owing to the nonradiation-based nature, the thermoresponsive polymer coated microfiber enables an improved thermal sensitivity of 18.74 nm/°C and, hence, a high-temperature resolution of millidegree. Furthermore, the micrometer-sized footprint enables its easy implantation in human organs for cellular thermometry and for the potential of in vivo applications.

"Bitter-Sweet" Polymeric Micelles Formed by Block Copolymers from Glucosamine and Cholic Acid

Natural compounds glucosamine and cholic acid have been used to make acrylic monomers which are subsequently used to prepare amphiphilic block copolymers by reversible addition-fragmentation chain transfer (RAFT) polymerization. Despite the striking difference in polarity and solubility, three diblock copolymers consisting of glucosamine and cholic acid pendants with different hydrophilic and hydrophobic chain lengths have been synthesized without the use of protecting groups. They are shown to self-assemble into polymeric micelles with a "bitter" bile acid core and "sweet" sugar shell in aqueous solutions, as evidenced by dynamic light scattering and transmission electron microscopy. The critical micelle concentration varies with the hydrophobic/hydrophilic ratio, ranging from 0.62 to 1.31 mg/L. Longer chains of polymers induced the formation of larger micelles in range of 50-70 nm. These micelles can solubilize hydrophobic compounds such as Nile Red in aqueous solutions. Their loading capacity mainly depends upon the hydrophobic/hydrophilic ratio of the polymers, and may be also related to the length of the hydrophilic block. These polymeric micelles allowed for a 10-fold increase in the aqueous solubility of paclitaxel and showed no cytotoxicity below the concentration of 500 mg/L. Such properties make these polymeric micelles interesting reservoirs for hydrophobic molecules and drugs for biomedical applications.