Preparation and in vitro evaluation of protective effects of Silibinin-loaded polymeric micelles on human hair against UV-B radiation

BACKGROUND

The purpose of this study was to investigate the protective effect of Silibinin-loaded polymeric micelles from human hair against UV-B radiation.

METHODS

Eight formulations with different concentrations of Silibinin, Pluronic F-127, and Labrasol-Labrafil were made by a solvent evaporation method, and the selected formulation was chosen by examining their properties like particle size and loading efficiency. Six groups of human hair, including a group that received the selected formulation, were exposed to UV-B radiation and by calculating its factors such as peak-to-valley roughness, RMS roughness, FTIR, and the amount of protein loss, the protective effect of the selected formulation was judged.

RESULTS

According to the results, the loading efficiency and particle size of the selected formulation were 45.34% and 43.19 nm. The Silibinin release profile had two parts, fast and slow, which were suitable for creating a drug depot on hair. Its zeta potential also confirmed the minimum electrostatic interference between the formulation and hair surface. The zeta potential of selected formulation was -5.9 mv. Examination of AFM images showed that the selected formulation was able to prevent the increase in peak-to-valley roughness and RMS roughness caused by UV-B radiation. RMS roughness after 600 h of UV radiation in Groups 5 and 6 was significantly lower than the negative control group and the amount of this factor did not differ significantly between 0 and 600, so it can be concluded that the selected formulation containing Silibinin and the positive control group was able to prevent the increase of RMS roughness and hair destruction. In other hands, the two positive control groups and the selected formulation containing Silibinin were able to effectively reduce hair protein loss.

CONCLUSION

Silibinin-loaded polymeric micelles were able to effectively protect hair from structural and chemical changes caused by UV-B radiation.

Bifunctional Smart Hydrogel Dressing with Strain Sensitivity and NIR-Responsive Performance

Smart response hydrogel has a broad application prospect in human health real-time monitoring due to its responses to a variety of stimuli. In this study, we developed a novel smart hydrogel dressing based on conductive MXene nanosheets and a temperature-sensitive PNIPAm polymer. γ-Methacryloxypropyltrimethoxysilane (KH570) was selected to functionalize the surface of MXene further to improve the interface compatibility between MXene and PNIPAm. Our prepared K-M/PNIPAm hydrogel was found to have a strain-sensitive property, as well as a respond to NIR phase change and volume change. When applied as a strain flexible sensor, this K-M/PNIPAm hydrogel exhibited a high strain sensitivity with a gauge factor (GF) of 4.491, a broad working strain range of ≈250%, a fast response of ∼160 ms, and good cycle stability (i.e., 3000 s at 20% strain). Besides, this K-M/PNIPAm hydrogel can be used as an efficient NIR light-controlled drug release carrier to achieve on-demand drug release. This work paved the way for the application of smart response hydrogel in human health real-time monitoring and NIR-controlled drug release functions.

Green Light-Triggered Intraocular Drug Release for Intravenous Chemotherapy of Retinoblastoma

Retinoblastoma is one of the most severe ocular diseases, of which current chemotherapy is limited to the repetitive intravitreal injections of chemotherapeutics. Systemic drug administration is a less invasive route; however, it is also less efficient for ocular drug delivery because of the existence of blood-retinal barrier and systemic side effects. Here, a photoresponsive drug release system is reported, which is self-assembled from photocleavable trigonal small molecules, to achieve light-triggered intraocular drug accumulation. After intravenous injection of drug-loaded nanocarriers, green light can trigger the disassembly of the nanocarriers in retinal blood vessels, which leads to intraocular drug release and accumulation to suppress retinoblastoma growth. This proof-of-concept study would advance the development of light-triggered drug release systems for the intravenous treatment of eye diseases.

Cyclodextrin Nanosponges Inclusion Compounds Associated with Gold Nanoparticles for Potential Application in the Photothermal Release of Melphalan and Cytoxan

This article describes the synthesis and characterization of β-cyclodextrin-based nano-sponges (NS) inclusion compounds (IC) with the anti-tumor drugs melphalan (MPH) and cytoxan (CYT), and the addition of gold nanoparticles (AuNPs) onto both systems, for the potential release of the drugs by means of laser irradiation. The NS-MPH and NS-CYT inclusion compounds were characterized using scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), UV-Vis, and proton nuclear magnetic resonance (1H-NMR). Thus, the inclusion of MPH and CYT inside the cavities of NSs was confirmed. The association of AuNPs with the ICs was confirmed by SEM, EDS, TEM, and UV-Vis. Drug release studies using NSs synthesized with different molar ratios of β-cyclodextrin and diphenylcarbonate (1:4 and 1:8) demonstrated that the ability of NSs to entrap and release the drug molecules depends on the crosslinking between the cyclodextrin monomers. Finally, irradiation assays using a continuous laser of 532 nm showed that photothermal drug release of both MPH and CYT from the cavities of NSs via plasmonic heating of AuNPs is possible.

Intelligent phototriggered nanoparticles induce a domino effect for multimodal tumor therapy

Rationale: Integration of several monotherapies into a single nanosystem can produce remarkable synergistic antitumor effects compared with separate delivery of combination therapies. We developed near-infrared (NIR) light-triggered nanoparticles that induce a domino effect for multimodal tumor therapy. Methods: The designed intelligent phototriggered nanoparticles (IPNs) were composed of a copper sulfide-loaded upconversion nanoparticle core, a thermosensitive and photosensitive enaminitrile molecule (EM) organogel shell loaded with anticancer drugs, and a cancer cell membrane coating. Irradiation with an NIR laser activated a domino effect beginning with photothermal generation by copper sulfide for photothermal therapy that also resulted in phase transformation of the EM gel to release the anticancer drug. Meanwhile, the NIR light energy was converted to ultraviolet light by the upconversion core to excite the EM, which generated reactive oxygen species for photodynamic therapy. Results: IPNs achieved excellent antitumor effects in vitro and in vivo with little systemic toxicity, indicating that IPNs could serve as a safe and high-performance instrument for synergetic antitumor therapy. Conclusion: This intelligent drug delivery system induced a chain reaction generating multiple antitumor therapies after a single stimulus.

On-Demand Reversible UV-Triggered Interpenetrating Polymer Network-Based Drug Delivery System Using the Spiropyran-Merocyanine Hydrophobicity Switch

A reversible switchable on-demand UV-triggered drug delivery system (DDS) based on interpenetrating polymer networks (IPNs) with silicone as the host polymer and spiropyran (SP)-functionalized guest polymer is designed and demonstrated. The photo-responsive IPNs provide a new triggered drug delivery concept as they exploit the change in intermolecular interactions (work of adhesion) among the drug, matrix, and solvent when the incorporated hydrophobic SP moieties transform into the hydrophilic merocyanine form upon light irradiation without degradation and disruption of the DDS. The change in how the copolymer composition (hydrophilicity and content) and the lipophilicity of the drug (log P) affect the release profile was investigated. A thermodynamic model, based on Hansen solubility parameters, was developed to design and optimize the polymer composition of the IPNs to obtain the most efficient light-triggered drug release and suppression of the premature release. The developed IPNs showed excellent result for dopamine, l-dopa, and prednisone with around 90-95% light-triggered release. The model was applied to study the release behavior of drugs with different log P and to estimate if the light-induced hydrophobic-to-hydrophilic switch can overcome the work of adhesion between polymers and drugs and hence the desorption and release of the drugs. To the best of our knowledge, this is the first time that work of adhesion is used for this aim. Comparing the result obtained from the model and experiment shows that the model is useful for evaluating and estimating the release behavior of specific drugs merocyanine, IPN, DDS, and spiropyran.

Photo-Responsive Supramolecular Micelles for Controlled Drug Release and Improved Chemotherapy

Development of stimuli-responsive supramolecular micelles that enable high levels of well-controlled drug release in cancer cells remains a grand challenge. Here, we encapsulated the antitumor drug doxorubicin (DOX) and pro-photosensitizer 5-aminolevulinic acid (5-ALA) within adenine-functionalized supramolecular micelles (A-PPG), in order to achieve effective drug delivery combined with photo-chemotherapy. The resulting DOX/5-ALA-loaded micelles exhibited excellent light and pH-responsive behavior in aqueous solution and high drug-entrapment stability in serum-rich media. A short duration (1-2 min) of laser irradiation with visible light induced the dissociation of the DOX/5-ALA complexes within the micelles, which disrupted micellular stability and resulted in rapid, immediate release of the physically entrapped drug from the micelles. In addition, in vitro assays of cellular reactive oxygen species generation and cellular internalization confirmed the drug-loaded micelles exhibited significantly enhanced cellular uptake after visible light irradiation, and that the light-triggered disassembly of micellar structures rapidly increased the production of reactive oxygen species within the cells. Importantly, flow cytometric analysis demonstrated that laser irradiation of cancer cells incubated with DOX/5-ALA-loaded A-PPG micelles effectively induced apoptotic cell death via endocytosis. Thus, this newly developed supramolecular system may offer a potential route towards improving the efficacy of synergistic chemotherapeutic approaches for cancer.

Construction of a Mesoporous Polydopamine@GO/Cellulose Nanofibril Composite Hydrogel with an Encapsulation Structure for Controllable Drug Release and Toxicity Shielding

The development of intelligent and multifunctional hydrogels having photothermal properties, good mechanical properties, sustained drug release abilities with low burst release, antibacterial properties, and biocompatibility is highly desirable in the biomaterial field. Herein, mesoporous polydopamine (MPDA) nanoparticles wrapped with graphene oxide (GO) were physically cross-linked in cellulose nanofibril (CNF) hydrogel to obtain a novel MPDA@GO/CNF composite hydrogel for controllable drug release. MPDA nanoparticles exhibited a high drug loading ratio (up to 35 wt %) for tetracycline hydrochloride (TH). GO was used to encapsulate MPDA nanoparticles for extending the drug release time and reinforcing the physical strength of the obtained hydrogel. The mechanical strength of the as-fabricated MPDA@GO/CNF composite hydrogel was five times greater compared to that of the pure CNF hydrogel. Drug release experiments demonstrated that burst release behavior was significantly reduced by adding MPDA@GO. The drug release time of the MPDA@GO/CNF composite hydrogel was 3 times and 7.2 times longer than that of the polydopamine/CNF hydrogel and pure CNF hydrogel, respectively. The sustained and controlled drug release behaviors of the composite hydrogel were highly dependent on the proportion of MPDA and GO. Moreover, the rate of drug release could be accelerated by near-infrared (NIR) light irradiation and pH value change. The drug release kinetics of the as-prepared composite hydrogel was well described by the Korsmeyer-Peppas model, and the drug release mechanism of TH from the composite hydrogel was anomalous transport. Importantly, this carefully designed MPDA@GO/CNF composite hydrogel showed good biocompatibility through an in vitro cytotoxicity test. In particular, the toxicity of GO was well shielded by the CNF hydrogel. Therefore, this novel MPDA@GO/CNF composite hydrogel with an encapsulation structure for controllable drug release and toxicity shielding of GO could be used as a very promising controlled drug delivery carrier, which may have potential applications for chemical and physical therapies.

Addressing the Biochemical Foundations of a Glucose-Based "Trojan Horse"-Strategy to Boron Neutron Capture Therapy: From Chemical Synthesis to In Vitro Assessment

Boron neutron capture therapy (BNCT) for cancer is on the rise worldwide due to recent developments of in-hospital neutron accelerators which are expected to revolutionize patient treatments. There is an urgent need for improved boron delivery agents, and herein we have focused on studying the biochemical foundations upon which a successful GLUT1-targeting strategy to BNCT could be based. By combining synthesis and molecular modeling with affinity and cytotoxicity studies, we unravel the mechanisms behind the considerable potential of appropriately designed glucoconjugates as boron delivery agents for BNCT. In addition to addressing the biochemical premises of the approach in detail, we report on a hit glucoconjugate which displays good cytocompatibility, aqueous solubility, high transporter affinity, and, crucially, an exceptional boron delivery capacity in the in vitro assessment thereby pointing toward the significant potential embedded in this approach.

Coumarin-Caged Compounds of 1-Naphthaleneacetic Acid as Light-Responsive Controlled-Release Plant Root Stimulators

Six coumarin-caged compounds of 1-naphthaleneacetic acid (NAA) comprising different substituents on the coumarin moiety were synthesized and evaluated for their photophysical and chemical properties as light-responsive controlled-release plant root stimulators. The ¹H NMR and HPLC techniques were used to verify the release of NAA from the caged compounds. After irradiation at 365 nm, the caged compounds exhibited the fastest release rate at t_1/2 of 6.7 days and the slowest release rate at t_1/2 of 73.7 days. Caged compounds at high concentrations (10^-5 and 10^-6 M) significantly stimulate secondary root germination while free NAA at the same level is toxic and leads to inhibition of secondary root germination. The cytotoxicity of the caged compounds against fibroblasts and vero cells were evaluated, and the results suggested that, at 10^-5-10^-6 M, caged compounds exhibited no significant cytotoxicity to the cells. Thus, the caged compounds of NAA in this study could be of great benefit as efficient agrochemicals.

Nanoparticle-Loaded Hydrogel for the Light-Activated Release and Photothermal Enhancement of Antimicrobial Peptides

Rising concerns over multidrug-resistant bacteria have necessitated an expansion to the current antimicrobial arsenal and forced the development of novel delivery strategies that enhance the efficacy of existing treatments. Antimicrobial peptides (AMPs) are a promising antibiotic alternative that physically disrupts the membrane of bacteria, resulting in rapid bactericidal activity; however, clinical translation of AMPs has been hindered by their susceptibility to protease degradation. Through the co-loading of liposomes encapsulating model AMP, IRIKIRIK-CONH₂ (IK8), and gold nanorods (AuNRs) into a poly(ethylene glycol) (PEG) hydrogel, we have demonstrated the ability to protect encapsulated materials from proteolysis and provide the first instance of the triggered AMP release. Laser irradiation at 860 nm, at 2.1 W cm^-2, for 10 min led to the photothermal triggered release of IK8, resulting in bactericidal activity against Gram-negative Pseudonomas aeruginosa and Gram-positive Staphylococcus aureus. Furthermore, by increasing the laser intensity to 2.4 W cm^-2, we have shown the thermal enhancement of AMP activity. The photothermal triggered release, and enhancement of AMP efficacy, was demonstrated to treat two rounds of fresh S. aureus, indicating that the therapeutic gel has the potential for multiple rounds of treatment. Taken together, this novel therapeutic hydrogel system demonstrates the stimuli-responsive release of AMPs with photothermal enhanced antimicrobial efficacy to treat pathogenic bacteria.

Injectable in Situ Forming Hydrogels of Thermosensitive Polypyrrole Nanoplatforms for Precisely Synergistic Photothermo-Chemotherapy

The combination of photothermal therapy (PTT) with chemotherapy has great potential to maximize the synergistic effect of thermo-induced chemosensitization and improve treatment performance. To achieve high drug-loading capacity as well as precise synchronization between the controllable release of chemotherapeutics and the duration of near-infrared PTT, in this work, a facile one-step method was first developed to fabricate a novel injectable in situ forming photothermal modulated hydrogel drug delivery platform (D-PPy@PNAs), in which a PNIPAM-based temperature-sensitive acidic triblock polymer [poly(acrylic acid-b-N-isopropylamide-b-acrylic acid (PNA)] was utilized as the stabilizing agent in the polymerization of polypyrrole (PPy). The in situ forming hydrogels showed a sensitive temperature-responsive sol-gel phase-transition behavior, as well as an excellent photothermal property. The strong interaction of ionic bonds together with π-π stacking interactions resulted in high doxorubicin (DOX) loading capacity and controlled/sustained drug release behavior. In addition, D-PPy@PNAs also displayed enhanced cellular uptake and promoted intratumoral penetration of DOX upon NIR laser irradiation. The synergistic photothermal therapy-chemotherapy of D-PPy@PNA hydrogels greatly improved the antitumor efficacy in vivo. Therefore, thermosensitive polypyrrole-based D-PPy@PNA hydrogels may be powerful drug delivery nanoplatforms for precisely synergistic photothermo-chemotherapy of tumors.

Ultrasonically and Iontophoretically Enhanced Drug-Delivery System Based on Dissolving Microneedle Patches

A multifunctional system comprised of hyaluronic acid microneedles was developed as an effective transdermal delivery platform for rapid local delivery. The microneedles can regulate the filling amount on the tip, by controlling the concentration of hyaluronic acid solution. Ultrasonication induces dissolution of the HA microneedles via vibration of acoustic pressure, and AC iontophoresis improves the electrostatic force-driven diffusion of HA ions and rhodamine B. The effect of ultrasound on rhodamine release was analyzed in vitro using a gelatin hydrogel. The frequency and voltage dependence of the AC on the ion induction transfer was also evaluated experimentally. The results showed that the permeability of the material acts as a key material property. The delivery system based on ultrasonication and iontophoresis in microneedles increases permeation, thus resulting in shorter initial delivery time than that required by delivery systems based on passive or ultrasonication alone. This study highlights the significance of the combination between ultrasonic waves and iontophoresis for improving the efficiency of the microneedles, by shortening the reaction duration. We anticipate that this system can be extended to macromolecular and dependence delivery, based on drug response time.

Light-Activable On-Demand Release of Nano-Antibiotic Platforms for Precise Synergy of Thermochemotherapy on Periodontitis

The overprescription and improper use of antibiotics have contributed to the evolution of bacterial resistance, making it urgent to develop alternative therapies and agents with better efficacy as well as less toxicity to combat bacterial infections and keep new resistance from developing. In this work, a novel light-activable nano-antibiotic platform (TC-PCM@GNC-PND) was constructed by the incorporation of gold nanocages (GNC) and two thermosensitive gatekeepers, phase-change materials (PCM) and thermosensitive polymer poly(N-isopropylacrylamide-co-diethylaminoethyl methacrylate) (PND), to realize precisely the synergy of photothermal and antimicrobial drugs. GNC exhibits an excellent photothermal effect owing to its strong absorbance in the near-infrared (NIR) region, and hollow interiors make it a favorable vehicle for loading various antibiotics such as tetracycline (TC). The release of the encapsulated drugs could be precisely controlled by NIR light through the dual thermosensitive interaction of liquid-solid transition of PCM and coil-granule transition of PND, improving efficacy and alleviating side effects with on-demand drug release. The thermosensitive hydrogel was formed in situ upon application with body temperature, enhancing retention of the antimicrobial agent in local infectious sites. Highly effective ablation of bacteria is achieved both in vitro and in periodontitis models with little toxicity owing to the synergy of photothermal effects and chemotherapeutic drug release induced by NIR. This study could provide guidance for the design of antibacterial materials and shed substantial light on synergistic treatment.

Extremely Effective Chemoradiotherapy by Inducing Immunogenic Cell Death and Radio-Triggered Drug Release under Hypoxia Alleviation

Local hypoxia in solid malignancies often results in resistance to radiotherapy (RT) and chemotherapy (CT), which may be one of the main reasons for their failure in clinical application. Especially, oxygen is an essential element for enhancing DNA damage caused by ionizing radiation in radiotherapy. Here, two biomimetic oxygen delivery systems were designed by encapsulating hemoglobin (Hb) alone into a liposome (Hb-Lipo) or co-encapsulating Hb and doxorubicin (DOX) into a liposome (DOX-Hb-Lipo). Our data indicated that both Hb-Lipo and DOX-Hb-Lipo could effectively alleviate hypoxia in tumors. We demonstrated that RT plus tumor-targeting delivery of oxygen mediated by Hb-Lipo could significantly overcome the tolerance of hypoxic cancer cells to RT, showing significantly enhanced cancer-cell killing and tumor growth inhibition ability, mainly attributing to hypoxia alleviation and increased reactive oxygen species production under RT in cancer cells. Furthermore, a melanoma model that was quite insensitive to both RT and CT was used to test the efficacy of chemoradiotherapy combined with hypoxia alleviation. RT plus Hb-Lipo only caused a limited increase in antitumor activity. However, extremely strong tumor inhibition could be obtained by RT combined with DOX-Hb-Lipo-mediated CT, attributed to radio-triggered DOX release and enhanced immunogenic cell death induced by RT under an oxygen supplement. Our study provided a valuable reference for overcoming hypoxia-induced radioresistance and a useful therapeutic strategy for cancers that are extremely insensitive to chemo- or radiotherapy.

Multi-Model Investigation and Adaptive Estimation of the Acoustic Release of a Model Drug From Liposomes

This paper researches a suitable mathematical model that can reliably predict the release of a model drug (namely calcein) from biologically targeted liposomal nanocarriers triggered by ultrasound. Using mathematical models, curve fitting is performed on a set of five experimental acoustic drug release runs from Albumin-, Estrone-, and RGD-based Drug Delivery Systems (DDS). The three moieties were chosen to target specific cancers using receptor-mediated endocytosis. The best-fitting mathematical model is then enhanced using a Kalman filtering (KF) algorithm to account for the statistics of the dynamic and measurements noise sequences in predicted drug release. Unbiased drug-release estimates are realized by implementing an online noise identification algorithm. The algorithm is first deployed in a simulated environment in which it was rigorously tested and compared with the correct solution. Then, the algorithm was used to process the five experimental datasets. The results suggest that the Adaptive Kalman Filter (AKF) is exceptionally good at handling drug release estimation problems with a priori unknown or with changing noise covariances. In comparison with the KF, the AKF approach exhibited as low as a 69% reduction in the level of error in estimating the drug release state. Finally, the proposed algorithm is not computationally demanding and is capable of online estimation tasks.

Light-Responsive Serinol-Based Polyurethane Nanocarrier for Controlled Drug Release

In the present work, a new and facile strategy for the synthesis of light-responsive polyurethanes (LrPUs) based on serinol with o-nitrobenzyl pendent groups is developed. Stable monodisperse nanoparticles from these LrPUs can be formulated reproducibly in a simple manner, which is shown by dynamic light scattering (DLS) measurements. Upon irradiation with UV light, both polymers and nanoparticles undergo rapid degradation, which is investigated by DLS, scanning electron microscopy, size exclusion chromatography, and UV-vis spectroscopy. The nanoparticles are also employed for the encapsulation of the model drug Nile Red, and by exposure to UV light, a burst release of the payload is detected via fluorescence spectroscopy. This strategy can be easily applied to the straightforward synthesis of various new serinol-based monomers with different stimuli-responsive properties and therefore expand the family of biodegradable polymers.

Protected Amino Acid-Based Hydrogels Incorporating Carbon Nanomaterials for Near-Infrared Irradiation-Triggered Drug Release

Molecular gels formed by the self-assembly of low-molecular-weight gelators have received increasing interest because of their potential applications in drug delivery. In particular, the ability of peptides and amino acids to spontaneously self-assemble into three-dimensional fibrous network has been exploited in the development of hydrogels. In this context, we have investigated the capacity of binary mixtures of aromatic amino acid derivatives to form hydrogels. Carbon nanomaterials, namely oxidized carbon nanotubes or graphene oxide, were incorporated in the two most stable hydrogels, formed by Fmoc-Tyr-OH/Fmoc-Tyr(Bzl)-OH and Fmoc-Phe-OH/Fmoc-Tyr(Bzl)-OH, respectively. The structural and physical properties of these gels were assessed using microscopic techniques and rheology. Circular dichroism and molecular dynamics simulations demonstrated that the hydrogel formation was mainly driven by aromatic interactions. Finally, a model hydrophilic drug (l-ascorbic acid) was loaded into the hybrid hydrogels at a high concentration. Under near-infrared light irradiation, a high amount of drug was released triggered by the heat generated by the carbon nanomaterials, thus offering interesting perspectives for controlled drug delivery.

Generic synthesis of small-sized hollow mesoporous organosilica nanoparticles for oxygen-independent X-ray-activated synergistic therapy

The success of radiotherapy relies on tumor-specific delivery of radiosensitizers to attenuate hypoxia resistance. Here we report an ammonia-assisted hot water etching strategy for the generic synthesis of a library of small-sized (sub-50 nm) hollow mesoporous organosilica nanoparticles (HMONs) with mono, double, triple, and even quadruple framework hybridization of diverse organic moieties by changing only the introduced bissilylated organosilica precursors. The biodegradable thioether-hybridized HMONs are chosen for efficient co-delivery of tert-butyl hydroperoxide (TBHP) and iron pentacarbonyl (Fe(CO)5). Distinct from conventional RT, radiodynamic therapy (RDT) is developed by taking advantage of X-ray-activated peroxy bond cleavage within TBHP to generate •OH, which can further attack Fe(CO)5 to release CO molecules for gas therapy. Detailed in vitro and in vivo studies reveal the X-ray-activated cascaded release of •OH and CO molecules from TBHP/Fe(CO)5 co-loaded PEGylated HMONs without reliance on oxygen, which brings about remarkable destructive effects against both normoxic and hypoxic cancers.

Stimuli-Responsive Nanomachines and Caps for Drug Delivery

In this review we focus on methods that are used to trap and release on command therapeutic drugs from mesoporous silica nanoparticles (MSNs). The pores in the MSNs are large enough to accommodate a wide range of cargo molecules such as anticancer and antibiotic drugs and yet small enough to be blocked by a variety of bulky molecules that act as caps. The caps are designed to be tightly attached to the pore openings and trap the cargo molecules without leakage, but upon application of a designed stimulus detach from the nanoparticles and release the cargo. Of special emphasis in this review are nanomachines that respond to stimuli administered from external sources such as light or magnetic fields, or from chemical stimuli produced by the biological system such as a general change in pH or redox potential, or a highly specific chemical produced by a cancer cell or infectious bacterium. The goal is to release a high local concentration of the cargo only where and when it is needed, thus minimizing off-target side effects. We discuss sophisticated reversible nanomachines but also discuss some useful caps that simply break off from the nanoparticles in response to the selected stimulus. Many ingenious systems have been and are being designed; we primarily highlight those that have been demonstrated to operate in vitro and/or in vivo. In most cases the closed MSNs are endocytosed by diseased or infected cells and opened inside the cells to release the drugs. We begin with an overview of the nanoparticles and nanomachines and then present examples of drug release triggered by internal chemical stimuli from the organism and finally by external light and magnetic field stimuli.

Synchronous Chemoradiation Nanovesicles by X-Ray Triggered Cascade of Drug Release

The approach of concurrent-to-synchronous chemoradiation has now been advanced by well-designed nanovesicles that permit X-ray irradiation-triggered instant drug release. The nanovesicles consist of Au nanoparticles tethered with irradiation labile linoleic acid hydroperoxide (LAHP) molecules and oxidation-responsive poly(propylene sulfide)-poly(ethylene glycol) (PPS-PEG) polymers, where DOX were loaded in the inner core of the vesicles (Au-LAHP-vDOX). Upon irradiation, the in situ formation of hydroxyl radicals from LAHP molecules triggers the internal oxidation of PPS from being hydrophobic to hydrophilic, leading to degradation of the vesicles and burst release of cargo drugs. In this manner, synchronous chemoradiation showed impressive anticancer efficacy both in vitro and in a subcutaneous mouse tumor model by one-dose injection and one-time irradiation.

Identification of the Uncertainty Structure to Estimate the Acoustic Release of Chemotherapeutics From Polymeric Micelles

This paper estimates the acoustic drug release from micelles after accurately identifying the underlying statistical noise characteristics in experimental data. The drug release is measured as a change in fluorescence as ultrasound is applied. First, the noise structure affecting the process dynamics and the measurement process is identified in terms of statistical covariance of the aforementioned quantities. Then, the identified covariance magnitudes are utilized to estimate the dynamics of drug release. The performance of different filters is investigated. The identified a priori knowledge is used to implement an optimal Kalman filter, a multi-hypothesis Kalman filter, and a variant of the full information estimator (moving horizon estimator) to the problem at hand. The proposed algorithms are initially deployed in a simulation environment, and then the experimental data sets are fed into the algorithms to validate their performance. Experiments span a number of ultrasonic power densities for both non-targeted and targeted polymeric micelles (the targeting being accomplished using the folate moiety). The results suggest that the proposed algorithm, the optimal Kalman filter, performs better than the other two in all tests performed.

A Thioacetal Photocage Designed for Dual Release: Application in the Quantitation of Therapeutic Release by Synchronous Reporter Decaging

Despite the immense potential of existing photocaging technology, its application is limited by the paucity of advanced caging tools. Here, we report on the design of a novel thioacetal ortho-nitrobenzaldehyde (TNB) dual arm photocage that enabled control of the simultaneous release of two payloads linked to a single TNB unit. By using this cage, which was prepared in a single step from commercial 6-nitroverataldehyde, three drug-fluorophore conjugates were synthesized: Taxol-TNB-fluorescein, Taxol-TNB-coumarin, and doxorubicin-TNB-coumarin, and long-wavelength UVA light-triggered release experiments demonstrated that dual payload release occurred with rapid decay kinetics for each conjugate. In cell-based assays performed in vitro, dual release could also be controlled by UV exposure, resulting in increased cellular fluorescence and cytotoxicity with potency equal to that of unmodified drug towards the KB carcinoma cell line. The extent of such dual release was quantifiable by reporter fluorescence measured in situ and was found to correlate with the extent of cytotoxicity. Thus, this novel dual arm cage strategy provides a valuable tool that enables both active control and real-time monitoring of drug activation at the delivery site.

A Donor-Acceptor Conjugated Polymer with Alternating Isoindigo Derivative and Bithiophene Units for Near-Infrared Modulated Cancer Thermo-Chemotherapy

Conjugated polymers containing alternating donor/acceptor units have strong and sharp absorbance peaks in near-infrared (NIR) region, which could be suitable for photothermal therapy. However, these polymers as photothermal transducers are rarely reported because of their water insolubility, which limits their applications for cancer therapy. Herein, we report the donor-acceptor conjugated polymer PBIBDF-BT with alternating isoindigo derivative (BIBDF) and bithiophene (BT) units as a novel photothermal transducer, which exhibited strong near-infrared (NIR) absorbance due to its low band gap (1.52 eV). To stabilize the conjugated polymer physiological environments, we utilized an amphiphilic copolymer, poly(ethylene glycol)-block-poly(hexyl ethylene phosphate) (mPEG-b-PHEP), to stabilize PBIBDF-BT-based nanoparticles (PBIBDF-BT@NPPPE) through a single emulsion method. The obtained nanoparticles PBIBDF-BT@NPPPE showed great stability in physiological environments and excellent photostability. Moreover, the PBIBDF-BT@NPPPE exhibited high photothermal conversion efficiency, reaching 46.7%, which is relatively high compared with those of commonly used materials for photothermal therapy. Accordingly, in vivo and in vitro experiments demonstrated that PBIBDF-BT@NPPPE exhibits efficient photothermal anticancer efficacy. More importantly, PBIBDF-BT@NPPPE could simultaneously encapsulate other types of therapeutic agents though hydrophobic interactions with the PHEP core and achieve NIR-triggered intracellular drug release and a synergistic combination therapy of thermo-chemotherapy for the treatment of cancer.

Rapid Light-Triggered Drug Release in Liposomes Containing Small Amounts of Unsaturated and Porphyrin-Phospholipids

Prompt membrane permeabilization is a requisite for liposomes designed for local stimuli-induced intravascular release of therapeutic payloads. Incorporation of a small amount (i.e., 5 molar percent) of an unsaturated phospholipid, such as dioleoylphosphatidylcholine (DOPC), accelerates near infrared (NIR) light-triggered doxorubicin release in porphyrin-phospholipid (PoP) liposomes by an order of magnitude. In physiological conditions in vitro, the loaded drug can be released in a minute under NIR irradiation, while liposomes maintain serum stability otherwise. This enables rapid laser-induced drug release using remarkably low amounts of PoP (i.e., 0.3 molar percent). Light-triggered drug release occurs concomitantly with DOPC and cholesterol oxidation, as detected by mass spectrometry. In the presence of an oxygen scavenger or an antioxidant, light-triggered drug release is inhibited, suggesting that the mechanism is related to singlet oxygen mediated oxidization of unsaturated lipids. Despite the irreversible modification of lipid composition, DOPC-containing PoP liposome permeabilization is transient. Human pancreatic xenograft growth in mice is significantly delayed with a single chemophototherapy treatment following intravenous administration of 6 mg kg(-1) doxorubicin, loaded in liposomes containing small amounts of DOPC and PoP.

Polymer-Coated Hollow Mesoporous Silica Nanoparticles for Triple-Responsive Drug Delivery

In this study, pH, reduction and light triple-responsive nanocarriers based on hollow mesoporous silica nanoparticles (HMSNs) modified with poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) were developed via surface-initiated atom transfer radical polymerization. Both reduction-cleavable disulfide bond and light-cleavable o-nitrobenzyl ester were used as the linkages between HMSNs and pH-sensitive PDEAEMA polymer caps. A series of characterization techniques were applied to characterize and confirm the structures of the intermediates and final nanocarriers. Doxorubicin (DOX) was easily encapsulated into the nanocarriers with a high loading capacity, and quickly released in response to the stimuli of reducing agent, acid environment or UV light irradiation. In addition, flow cytometry analysis, confocal laser scanning microscopy observations and cytotoxicity studies indicated that the nanocarriers were efficiently internalized by HeLa cancer cells, exhibiting (i) enhanced release of DOX into the cytoplasm under external UV light irradiation, (ii) better cytotoxicity against HeLa cells, and (iii) superior control over drug delivery and release. Thus, the triple-responsive nanocarriers present highly promising potentials as a drug delivery platform for cancer therapy.