Light-Addressable Capsules as Caged Compound Matrix for Controlled Triggering of Cytosolic Reactions

Synthesizing Submicron Polyelectrolyte Capsules to Boost Enzyme Immobilization and Enhance Enzyme-Based Immunoassays

Polyelectrolyte capsules (PCs) exhibit attractive superiorities in enzyme immobilization, including providing a capacious microenvironment for enzyme conformational freedom, highly effective mass transfer, and protecting enzymes from the external environment. Herein, we provide the first systemic evaluation of submicron PCs (SPCs, 500 nm) for enzyme immobilization. The catalytic kinetics results show that SPC encapsulation affected the affinities of enzymes and substrates but significantly enhanced their catalytic activity. The stability test indicates that SPC-encapsulated horseradish peroxidase (HRP) exhibits ultrahigh resistance to external harsh conditions and has a longer storage life than that of soluble HRP. The proposed encapsulation strategy enables 7.73-, 2.22-, and 11.66-fold relative activities when working at a pH as low as 3, at a NaCl concentration as high as 500 mM, and at a trypsin concentration as high as 10 mg/mL. We find that SPC encapsulation accelerates the cascade reaction efficiency of HRP and glucose oxidase. Owing to SPCs enhancing the catalytic activity of the loaded enzymes, we established an amplified enzyme-linked immunosorbent assay (ELISA) for the detection of Escherichia coli O157:H7 using HRP-loaded SPCs. The detection sensitivity of SPC-improved ELISA was found to be 280 times greater than that of conventional HRP-based ELISA. Altogether, we provide an elaborate evaluation of 500 nm SPCs on enzyme immobilization and its application in the ultrasensitive detection of foodborne pathogens. This evaluation provides evidence to reveal the potential advantage of SPCs on enzyme immobilization for enzyme-based immunoassays. It has excellent biological activity and strong stability and broadens the application prospect in urine, soy sauce, sewage, and other special samples.

Transport of Magnetic Polyelectrolyte Capsules in Various Environments

Microcapsules consisting of eleven layers of polyelectrolyte and one layer of iron oxide nanoparticles were fabricated. Two types of nanoparticles were inserted as one of the layers within the microcapsule’s walls: Fe2O3, ferric oxide, having a mean diameter (Ø) of 50 nm and superparamagnetic Fe3O4 having Ø 15 nm. The microcapsules were suspended in liquid environments at a concentration of 108 caps/mL. The suspensions were pumped through a tube over a permanent magnet, and the accumulation within a minute was more than 90% of the initial concentration. The design of the capsules, the amount of iron embedded in the microcapsule, and the viscosity of the transportation fluid had a rather small influence on the accumulation capacity. Magnetic microcapsules have broad applications from cancer treatment to molecular communication.

Stimulation of Local Cytosolic Calcium Release by Photothermal Heating for Studying Intra- and Intercellular Calcium Waves

A methodology is described that allows for localized Ca2+ release by photoexcitation. For this, cells are loaded with polymer capsules with integrated plasmonic nanoparticles, which reside in endo-lysosomes. The micrometer-sized capsules can be individually excited by near-infrared light from a light pointer, causing photothermal heating, upon which there is a rise in the free cytosolic Ca2+ concentration ([Ca2+ ]i ). The [Ca2+ ]i can be analyzed with a Ca2+ indicator fluorophore. In this way, it is possible to excite local lysosomal Ca2+ release in a desired target cell.

Quantitative Assessment of Endosomal Escape of Various Endocytosed Polymer-Encapsulated Molecular Cargos upon Photothermal Heating

Encapsulated molecular cargos are efficiently endocytosed by cells. For cytosolic delivery, understanding the dynamic process of cargos release from the carrier vehicles used for encapsulation and the lysosomes where the carrier vehicles are trapped (which in general is the bottleneck), followed by diffusion in the cytosol is important for improving drug/gene delivery strategies. A methodology is reported to image this process on a millisecond scale and to quantitatively analyze the data. Polyelectrolyte capsules with embedded gold nanostars to encapsulate 43 fluorescent molecular cargos with diverse properties, ranging from small fluorophores to fluorescently labeled proteins, siRNA, etc., are used. By short laser irradiation intracellular release of the molecular cargos from endocytosed capsules into the cytosol is triggered, and their intracellular spreading is imaged. Most of the released molecular cargos evenly distribute inside the entire cell, while others are enriched in certain cell compartments. The time the different molecular cargos take to distribute within cells, i.e., the spreading time, is used as a quantifier. Quantitative analysis reveals that intracellular spread cannot be described by free diffusion, but is determined by interaction of the molecular cargo with intracellular components.

Development of Silica-Based Biodegradable Submicrometric Carriers and Investigating Their Characteristics as in Vitro Delivery Vehicles

Nanostructured silica (SiO2)-based materials are attractive carriers for the delivery of bioactive compounds into cells. In this study, we developed hollow submicrometric particles composed of SiO2 capsules that were separately loaded with various bioactive molecules such as dextran, proteins, and nucleic acids. The structural characterization of the reported carriers was conducted using transmission and scanning electron microscopies (TEM/SEM), confocal laser scanning microscopy (CLSM), and dynamic light scattering (DLS). Moreover, the interaction of the developed carriers with cell lines was studied using standard viability, proliferation, and uptake assays. The submicrometric SiO2-based capsules loaded with DNA plasmid encoding green fluorescence proteins (GFP) were used to transfect cell lines. The obtained results were compared with studies made with similar capsules composed of polymers and show that SiO2-based capsules provide better transfection rates on the costs of higher toxicity.

Magnetic polyelectrolyte microcapsules via water-in-water droplet microfluidics

Polyelectrolyte microcapsules (PEMCs) have biocompatible microcompartments. Therefore, PEMCs are useful for applications in cosmetics, food, pharmaceutics, and other industries. The fabrication of PEMCs often involves the use of harsh chemicals or cytotoxic organic phases that make biomedical applications of the microcapsules challenging. In this report, we present an all-aqueous droplet microfluidics platform for the generation of magnetic PEMCs. In the platform, we use an aqueous-two-phase system (ATPS) of polyethylene glycol (PEG) and dextran (Dex), to generate water-in-water droplets, which are magnetically functionalized with ferrofluid. Strong polyelectrolytes (PEs) with opposite charges are used in each ATPS phase. We make emulsion templates of magnetic Dex, containing the polycations, in a continuous phase of PEG. We then apply a magnetic field to move the magnetic droplets to a second PEG phase, which contains the polyanions. By careful tuning of the fluxes of the two PEs in their respective phases, we trigger the formation of a shell at the droplet interface. Owing to the presence of the ferrofluid, the resulting microcapsules are magnetically responsive. We show that the magnetic PEMCs are capable of passive release of large pseudo-drugs as well as triggered release using external stimuli such as osmotic shock and pH change. We expect that magnetic PEMCs from this biocompatible all-aqueous platform will find utility in the fabrication of functionalized drug carriers for targeted drug delivery.

Nanomedicine and Onco-Immunotherapy: From the Bench to Bedside to Biomarkers

The broad relationship between the immune system and cancer is opening a new hallmark to explore for nanomedicine. Here, all the common and synergy points between both areas are reviewed and described, and the recent approaches which show the progress from the bench to the beside to biomarkers developed in nanomedicine and onco-immunotherapy.

Thermoplasmonic-Triggered Release of Loads from DNA-Modified Hydrogel Microcapsules Functionalized with Au Nanoparticles or Au Nanorods

Microcapsules consisting of hydrogel shells cross-linked by glucosamine-boronate ester complexes and duplex nucleic acids, loaded with dyes or drugs and functionalized with Au nanoparticles (Au NPs) or Au nanorods (Au NRs), are developed. Irradiation of Au NPs or Au NRs results in the thermoplasmonic heating of the microcapsules, and the dissociation of the nucleic acid cross-linkers. The separation of duplex nucleic acid cross-linkers leads to low-stiffness hydrogel shells, allowing the release of loads. Switching off the light-induced plasmonic heating results in the regeneration of stiff hydrogel shells protecting the microcapsules, leading to the blockage of release processes. The thermoplasmonic release of tetramethylrhodamine-dextran, Texas Red-dextran, doxorubicin-dextran (DOX-D), or camptothecin-carboxymethylcellulose (CPT-CMC) from the microcapsules is introduced. By loading the microcapsules with two different drugs (DOX-D and CPT-CMC), the light-controlled dose release is demonstrated. Cellular experiments show efficient permeation of Au NPs/DOX-D or Au NRs/DOX-D microcapsules into MDA-MB-231 cancer cells and inefficient uptake by MCF-10A epithelial breast cells. Cytotoxicity experiments reveal selective thermoplasmon-induced cytotoxicity of the microcapsules toward MDA-MB-231 cancer cells as compared to MCF-10A cells. Also, selective cytotoxicity towards MDA-MB-231 cancer cells upon irradiation of the Au NPs- and Au NRs-functionalized microcapsules at λ = 532 or 910 nm is demonstrated.

Quantitative Particle Uptake by Cells as Analyzed by Different Methods

There is a large number of two-dimensional static in vitro studies about the uptake of colloidal nano- and microparticles, which has been published in the last decade. In this Minireview, different methods used for such studies are summarized and critically discussed. Supplementary experimental data allow for a direct comparison of the different techniques. Emphasis is given on how quantitative parameters can be extracted from studies in which different experimental techniques have been used, with the goal of allowing better comparison.

Encapsulation of Enzymes in Porous Capsules via Particle Templating

The entrapment of enzymes in capsules is a smart strategy to concentrate them in confined spaces and control their exposure to outside environments. Enzymes can be caged in the interior of capsules during their formation (preloading) or postloaded within prefabricated and permeable hollow shells. On the other hand, enzymes can also be deposited within the shell or on the surface of the capsules. Each of these strategies has intrinsic limitations, and a common enemy is the undesired desorption of enzymes.Here, we describe the formation of enzyme-loaded polymeric capsules prepared with the Layer-by-Layer method and the template-assisted entrapment of enzymes through coprecipitation (preloading) within calcium carbonate particles, as an example of an efficient preloading strategy, and draw attention at the key parameters that influence this immobilization method.

RGD-functionalized magnetosomes are efficient tumor radioenhancers for X-rays and protons

Although chemically synthesized ferro/ferrimagnetic nanoparticles have attracted great attention in cancer theranostics, they lack radio-enhancement efficacy due to low targeting and internalization ability. Herein, we investigated the potential of RGD-tagged magnetosomes, bacterial biogenic magnetic nanoparticles naturally coated with a biological membrane and genetically engineered to express an RGD peptide, as tumor radioenhancers for conventional radiotherapy and proton therapy. Although native and RGD-magnetosomes similarly enhanced radiation-induced damage to plasmid DNA, RGD-magnetoprobes were able to boost the efficacy of radiotherapy to a much larger extent than native magnetosomes both on cancer cells and in tumors. Combined to magnetosomes@RGD, proton therapy exceeded the efficacy of X-rays at equivalent doses. Also, increased secondary emissions were measured after irradiation of magnetosomes with protons versus photons. Our results indicate the therapeutic advantage of using functionalized magnetoparticles to sensitize tumors to both X-rays and protons and strengthen the case for developing biogenic magnetoparticles for multimodal nanomedicine in cancer therapy.

Fiber Optofluidic Technology Based on Optical Force and Photothermal Effects

Optofluidics is an exciting new area of study resulting from the fusion of microfluidics and photonics. It broadens the application and extends the functionality of microfluidics and has been extensively investigated in biocontrol, molecular diagnosis, material synthesis, and drug delivery. When light interacts with a microfluidic system, optical force and/or photothermal effects may occur due to the strong interaction between light and liquid. Such opto-physical effects can be used for optical manipulation and sensing due to their unique advantages over conventional microfluidics and photonics, including their simple fabrication process, flexible manipulation capability, compact configuration, and low cost. In this review, we summarize the latest progress in fiber optofluidic (FOF) technology based on optical force and photothermal effects in manipulation and sensing applications. Optical force can be used for optofluidic manipulation and sensing in two categories: stable single optical traps and stable combined optical traps. The photothermal effect can be applied to optofluidics based on two major structures: optical microfibers and optical fiber tips. The advantages and disadvantages of each FOF technology are also discussed.

Hybrids of Polymeric Capsules, Lipids, and Nanoparticles: Thermodynamics and Temperature Rise at the Nanoscale and Emerging Applications

The importance of thermodynamics does not need to be emphasized. Indeed, elevated temperature processes govern not only industrial scale production but also self-assembly, chemical reaction, interaction between molecules, etc. Not surprisingly, biological processes typically take place at a specific temperature. Here, we look at possibilities to raise the localized temperature by a laser around noble-metal nanoparticles incorporated into shells of layer-by-layer polyelectrolyte microcapsules-freely suspended delivery vehicles in an aqueous solution, developed in the Department of Interfaces, Max Planck Institute of Colloids and Interfaces, headed by Helmuth Möhwald. Understanding the mechanisms of localized temperature rise is essential, that is why we analyze the influence of incident intensity, nanoparticle size, their distribution and aggregation state, as well as thermodynamics at the nanoscale. This leads us to scrutinize "global" (used for thermal encapsulation) versus "local" (used for release of encapsulated materials) temperature rise. Similar analysis is extended to planar polymeric coatings, the lipid membrane system of vesicles and cells, on which nanoparticles are adsorbed. Insights are provided into the mechanisms of physicochemical and biological effects, the nature of which has always been profoundly, interactively, and engagingly discussed in the Department of Interfaces. This analysis is combined with recent developments providing outlook and highlighting a broad range of emerging applications.

The Future of Layer-by-Layer Assembly: A Tribute to ACS Nano Associate Editor Helmuth Möhwald

Layer-by-layer (LbL) assembly is a widely used tool for engineering materials and coatings. In this Perspective, dedicated to the memory of ACS Nano associate editor Prof. Dr. Helmuth Möhwald, we discuss the developments and applications that are to come in LbL assembly, focusing on coatings, bulk materials, membranes, nanocomposites, and delivery vehicles.

Multilayer Capsules Inside Biological Systems: State-of-the-Art and Open Challenges

There are many reports about the interaction of multilayer capsules with biological systems in the literature. A majority of them are devoted to the in vitro study with two-dimensional cell cultures. Multilayer capsule fabrication had been under intensive investigation from 1990s and 2000s by Prof. Helmuth Möhwald, and many of his followers further developed their own research directions, focusing on capsule implementation in various fields of biology and medicine. The aim of this future article is to consistently consider the most recent advances in cell-capsule interactions for different biomedical applications, including functionalization of clinically relevant cells, nonviral gene delivery, magnetization of cells to control their movement, and in vivo drug delivery. Finally, the description and discussion of the new trends and perspectives for improved functionalities of capsules in design and functionalization of cell-assisted drug vehicles are the major topics of this work.

Remotely controlled opening of delivery vehicles and release of cargo by external triggers

Tremendous efforts have been devoted to the development of future nanomedicines that can be specifically designed to incorporate responsive elements that undergo modification in structural properties upon external triggers. One potential use of such stimuli-responsive materials is to release encapsulated cargo upon excitation by an external trigger. Today, such stimuli-response materials allow for spatial and temporal tunability, which enables the controlled delivery of compounds in a specific and dose-dependent manner. This potentially is of great interest for medicine (e.g. allowing for remotely controlled drug delivery to cells, etc.). Among the different external exogenous and endogenous stimuli used to control the desired release, light and magnetic fields offer interesting possibilities, allowing defined, real time control of intracellular releases. In this review we highlight the use of stimuli-responsive controlled release systems that are able to respond to light and magnetic field triggers for controlling the release of encapsulated cargo inside cells. We discuss established approaches and technologies and describe prominent examples. Special attention is devoted towards polymer capsules and polymer vesicles as containers for encapsulated cargo molecules. The advantages and disadvantages of this methodology in both, in vitro and in vivo models are discussed. An overview of challenges associate with the successful translation of those stimuli-responsive materials towards future applications in the direction of potential clinical use is given.

Activatable cell-biomaterial interfacing with photo-caged peptides

We report an effective strategy to design activatable cell–material interfacing systems enabling photo-modulated cellular entry of cargoes and cell adhesion towards surfaces.

Spatio-temporally tailoring cell–material interactions is essential for developing smart delivery systems and intelligent biointerfaces. Here we report new photo-activatable cell–material interfacing systems that trigger cellular uptake of various cargoes and cell adhesion towards surfaces. To achieve this, we designed a novel photo-caged peptide which undergoes a structural transition from an antifouling ligand to a cell-penetrating peptide upon photo-irradiation. When the peptide is conjugated to ligands of interest, we demonstrate the photo-activated cellular uptake of a wide range of cargoes, including small fluorophores, proteins, inorganic (e.g., quantum dots and gold nanostars) and organic nanomaterials (e.g., polymeric particles), and liposomes. Using this system, we can remotely regulate drug administration into cancer cells by functionalizing camptothecin-loaded polymeric nanoparticles with our synthetic peptide ligands. Furthermore, we show light-controlled cell adhesion on a peptide-modified surface and 3D spatiotemporal control over cellular uptake of nanoparticles using two-photon excitation. We anticipate that the innovative approach proposed in this work will help to establish new stimuli-responsive delivery systems and biomaterials.

Erythrocyte Membrane Modified Janus Polymeric Motors for Thrombus Therapy

We report the construction of erythrocyte membrane-cloaked Janus polymeric motors (EM-JPMs) which are propelled by near-infrared (NIR) laser irradiation and are successfully applied in thrombus ablation. Chitosan (a natural polysaccharide with positive charge, CHI) and heparin (glycosaminoglycan with negative charge, Hep) were selected as wall materials to construct biodegradable and biocompatible capsules through the layer-by-layer self-assembly technique. By partially coating the capsule with a gold (Au) layer through sputter coating, a NIR-responsive Janus structure was obtained. Due to the asymmetric distribution of Au, a local thermal gradient was generated upon NIR irradiation, resulting in the movement of the JPMs through the self-thermophoresis effect. The reversible "on/off" motion of the JPMs and their motile behavior were easily tuned by the incident NIR laser intensity. After biointerfacing the Janus capsules with an erythrocyte membrane, the EM-JPMs displayed red blood cell related properties, which enabled them to move efficiently in relevant biological environments (cell culture, serum, and blood). Furthermore, this therapeutic platform exhibited excellent performance in ablation of thrombus through photothermal therapy. As man-made micromotors, these biohybrid EM-JPMs hold great promise of navigating in vivo for active delivery while overcoming the drawbacks of existing synthetic therapeutic platforms. We expect that this biohybrid motor has considerable potential to be widely used in the biomedical field.

Photoresponsive and Magnetoresponsive Graphene Oxide Microcapsules Fabricated by Droplet Microfluidics

Fluid compartmentalization by microencapsulation is important in scenarios where protection or controlled release of encapsulated species, or isolation of chemical transformations is the central concern. Realizing responsive encapsulation systems by incorporating functional nanomaterials is of particular interest. We report here on the development of graphene oxide microcapsules enabled by a single-step microfluidic process. Interfacial reaction of epoxide-bearing graphene oxide sheets and an amine-functionalized macromolecular silicone fluid creates a chemically cross-linked film with micronscale thickness at the surface of water-in-oil droplets generated by microfluidic devices. The resulting microcapsules are monodisperse, mechanically resilient, and shape-tunable constructs. Ferrite nanoparticles are incorporated via the aqueous phase and enable microcapsule positioning by a magnetic field. We exploit the photothermal response of graphene oxide to realize microcapsules with photoresponsive release characteristics and show that the microcapsule permeability is significantly enhanced by near-IR illumination. The dual magnetic and photoresponsive characteristics, combined with the use of a single-step process employing biocompatible fluids, represent highly compelling aspects for practical applications.

Composite Polymer Colloids for SERS-Based Applications

Polymers and nanoparticles can be combined into different materials with applications in various fields like catalysis, biotechnology, or drug delivery, to cite just a few. Colloidal composites may vary significantly, ranging from a single nanoparticle stabilized by a polymer shell through a polymeric carrier decorated with hundreds of particles. We review here composite colloids comprising gold nanoparticles, with an emphasis in systems with potential application in surface enhanced Raman scattering (SERS). The focus is on selected strategies for synthesis and functionalization, such as: encapsulation of gold nanoparticles by amphiphilic polymers, polymeric matrices as nanoparticle carriers and smart polymer based composites. We stress the benefits derived from the combination of polymers and metal particles toward SERS, such as chemical and colloidal stabilization in complex environments, and collective optical effects through hot spot generation for optimized SERS enhancement or improved imaging tags.

Polymeric and Lipid Membranes-From Spheres to Flat Membranes and vice versa

Membranes are important components in a number of systems, where separation and control of the flow of molecules is desirable. Controllable membranes represent an even more coveted and desirable entity and their development is considered to be the next step of development. Typically, membranes are considered on flat surfaces, but spherical capsules possess a perfect "infinite" or fully suspended membranes. Similarities and transitions between spherical and flat membranes are discussed, while applications of membranes are also emphasized.

pH- and ligand-induced release of loads from DNA-acrylamide hydrogel microcapsules

Herein, a method to construct stimuli-responsive DNA-acrylamide-based hydrogel microcapsules has been presented. This method involves the use of polyacrylamide chains modified with predesigned nucleic acid hairpin units and optionally single-strand tethers that provide the required hybridization and recognition functions to yield substrate-loaded stimuli-responsive hydrogel-based microcapsules. The synthesis of the microcapsules involves the loading of CaCO3 microparticles with the respective load substrates and the functionalization of the CaCO3 template particles with nucleic acid promoter units. In the presence of the hairpin-modified acrylamide chains, the promoter units induce the hybridization chain reaction (HCR), which leads to the formation of a hydrogel coating, which, after the dissociation of the CaCO3 cores, yields substrate-loaded stimuli-responsive hydrogel microcapsules. One of the microcapsule systems includes, in the hairpin-modified acrylamide constructs, and in the subsequent HCR-generated hydrogel shells, the caged sequences of anti-ATP or anti-cocaine aptamers. In the presence of ATP or cocaine, the duplex-caged aptamer sequences are separated via the formation of ATP- or cocaine-aptamer complexes, which results in the partial separation of the microcapsules and the release of the loads. The second type of microcapsule is cooperatively stabilized by bridges generated by HCR and pH-sensitive duplex units. Under acidic conditions, the pH-sensitive bridges dissociate via the formation of i-motif structures, which results in an increase in the fluidity of the microcapsule shells and the release of the loads. Preliminary studies indicate that ATP- or pH-responsive microcapsules loaded with the anticancer drug, doxorubicin, have a selective cytotoxic effect on MDA-MB-231 cancer cells.

Diverse Applications of Nanomedicine

The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic.

Ultrafast Near-Infrared Light-triggered Intracellular Uncaging to Probe Cell Signaling

The possibility of regulating cell signaling with high spatial and temporal resolution within individual cells and complex cellular networks has important implications in biomedicine. In this report, we demonstrate a general strategy that uses near-infrared tissue-penetrating laser pulses to uncage biomolecules from plasmonic gold-coated liposomes, i.e. plasmonic liposomes, to activate cell signaling in a non-thermal, ultrafast and highly controllable fashion. Near-infrared picosecond laser pulse induces transient nanobubbles around plasmonic liposomes. The mechanical force generated from the collapse of nanobubbles rapidly ejects encapsulated compound within 0.1 ms. We showed that single pulse irradiation triggers the rapid intracellular uncaging of calcein from plasmonic liposomes inside endo-lysosomes. The uncaged calcein then evenly distributes over the entire cytosol and nucleus. Furthermore, we demonstrated the ability to trigger calcium signaling in both an immortalized cell line and primary dorsal root ganglion (DRG) neurons by intracellular uncaging of inositol triphosphate (IP3), an endogenous cell calcium signaling second messenger. Compared with other uncaging techniques, this ultrafast near-infrared light-driven molecular uncaging method is easily adaptable to deliver a wide range of bioactive molecules with an ultrafast optical switch, enabling new possibilities to investigate signaling pathways within individual cells and cellular networks.

Cathepsin B-degradable, NIR-responsive nanoparticulate platform for target-specific cancer therapy

Stimuli-responsive anticancer formulations can promote drug release and activation within the target tumour, facilitate cellular uptake, as well as improve the therapeutic efficacy of drugs and reduce off-target effects. In the present work, indocyanine green (ICG)-containing polyglutamate (PGA) nanoparticles were developed and characterized. Digestion of nanoparticles with cathepsin B, a matrix metalloproteinase overexpressed in the microenvironment of advanced tumours, decreased particle size and increased ICG cellular uptake. Incorporation of ICG in PGA nanoparticles provided the NIR-absorbing agent with time-dependent altered optical properties in the presence of cathepsin B. Having minimal dark toxicity, the formulation exhibited significant cytotoxicity upon NIR exposure. Combined use of the formulation with saporin, a ribosome-inactivating protein, resulted in synergistically enhanced cytotoxicity attributed to the photo-induced release of saporin from endo/lysosomes. The results suggest that this therapeutic approach can offer significant therapeutic benefit in the treatment of superficial malignancies, such as head and neck tumours.

Nanoparticles for radiooncology: Mission, vision, challenges

Cancer is one of the leading non-communicable diseases with highest mortality rates worldwide. About half of all cancer patients receive radiation treatment in the course of their disease. However, treatment outcome and curative potential of radiotherapy is often impeded by genetically and/or environmentally driven mechanisms of tumor radioresistance and normal tissue radiotoxicity. While nanomedicine-based tools for imaging, dosimetry and treatment are potential keys to the improvement of therapeutic efficacy and reducing side effects, radiotherapy is an established technique to eradicate the tumor cells. In order to progress the introduction of nanoparticles in radiooncology, due to the highly interdisciplinary nature, expertise in chemistry, radiobiology and translational research is needed. In this report recent insights and promising policies to design nanotechnology-based therapeutics for tumor radiosensitization will be discussed. An attempt is made to cover the entire field from preclinical development to clinical studies. Hence, this report illustrates (1) the radio- and tumor-biological rationales for combining nanostructures with radiotherapy, (2) tumor-site targeting strategies and mechanisms of cellular uptake, (3) biological response hypotheses for new nanomaterials of interest, and (4) challenges to translate the research findings into clinical trials.

Photo-Modulated Therapeutic Protein Release from a Hydrogel Depot Using Visible Light

The use of biomacromolecular therapeutics has revolutionized disease treatment, but frequent injections are required owing to their short half-life in vivo. Thus there is a need for a drug delivery system that acts as a reservoir and releases the drug remotely "on demand". Here we demonstrate a simple light-triggered local drug delivery system through photo-thermal interactions of polymer-coated gold nanoparticles (AuNPs) inside an agarose hydrogel as therapeutic depot. Localized temperature increase induced by the visible light exposure caused reversible softening of the hydrogel matrix to release the pre-loaded therapeutics. The release profile can be adjusted by AuNPs and agarose concentrations, light intensity and exposure time. Importantly, the biological activity of the released bevacizumab was highly retained. In this study we demonstrate the potential application of this facile AuNPs/hydrogel system for ocular therapeutics delivery through its versatility to release multiple biologics, compatibility to ocular cells and spatiotemporal control using visible light.

Bombardment induced ion transport - part IV: ionic conductivity of ultra-thin polyelectrolyte multilayer films

The dependence of the ionic conductance of ultra-thin polyelectrolyte multilayer (PEM) films on the temperature and the number of bilayers has been investigated by the recently developed low energy bombardment induced ion transport (BIIT) method. To this end multilayers of alternating poly(sodium 4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) layers were deposited on a metal electrode and subsequently bombarded by a low energy potassium ion beam. Ions are transported through the film according to the laws of electro-diffusion towards a grounded backside electrode. They are neutralized at the interface between the polymer film and the metal electrode. The detected neutralization current scales linearly with the acceleration potential of the ion beam indicating Ohmic behavior for the (PAH/PSS)x multilayer, where x denotes the number of bilayers. The conductance exhibits a non-monotonic dependence on the number of bilayers, x. For 2 ≤ x ≤ 8 the conductance increases non-linearly with the number of bilayers. For x ≥ 8 the conductance decreases with increasing number of bilayers. The variation of the conductance is rationalized by a model accounting for the structure dependence of the conductivity. The thinnest sample for which the conductance has been measured is the single bilayer reflecting properties dominated by the interface. The activation energy for the ion transport is 0.49 eV.

Control of Wnt/β-Catenin Signaling Pathway in Vivo via Light Responsive Capsules

The possibility to remotely manipulate intracellular pathways in single cells is among the current goals of biomedicine, demanding new strategies to control cell function and reprogramming cell fate upon external triggering. Optogenetics is one approach in this direction, allowing specific cell stimulation by external illumination. Here, we developed optical switchers of an ancient and highly conserved system controlling a variety of developmental and adult processes in all metazoans, from Hydra to mammals, the Wnt/β-catenin signaling pathway. An intracellular modulator of the Wnt pathway was enclosed into polyelectrolyte multilayer microcapsules engineered to include self-tracking (i.e., fluorescence labeling) and light mediated heating functionalities (i.e., plasmonic nanoparticles). Capsules were delivered in vivo to Hydra and NIR triggered drug release caused forced activation of the Wnt pathway. The possibility to remotely manipulate the Wnt pathway by optical switchers may be broadly translated to achieve spatiotemporal control of cell fate for new therapeutic strategies.

Sequential co-delivery of miR-21 inhibitor followed by burst release doxorubicin using NIR-responsive hollow gold nanoparticle to enhance anticancer efficacy

Previous literature and our study showed the delivery sequence of microRNA inhibitor and chemotherapeutic compounds achieve distinct therapeutic anticancer efficacy. Yet, it is challenging to use nanoparticle to achieve sequential drug delivery. In the current study, we designed sequential co-delivery system using a near-infrared-radiation (NIR) responsive hollow gold nanoparticle (HGNPs) to achieve sequential release of microRNA inhibitor (miR-21i)/doxirubicin(Dox) in order to achieve synergistic efficacy. PAMAM modified HGNPs was used to encapsulate miR-21i and Dox. Upon entering tumor cells, miRNA-21i was released first to sensitize the cancer cells, the subsequent burst release of Dox was achieved by NIR triggered collapse of HGNPs. This sequential delivery of miRNA-21i and Dox produced a synergistic apoptotic response, thereby enhancing anticancer efficacy by 8-fold and increasing anti-cancer stem cell activity by 50-fold. The sequential delivery of miR-21i and Dox using HGNPs under NIR after intravenous administration showed high tumor accumulation and significantly improved efficacy, which was 4-fold compared to free Dox group. These data suggested that the sequential co-delivery of miR-21i followed by burst release Dox using NIR-responsive HGNPs sensitized cancer cells to chemotherapeutic compound, which provided a novel concept for co-delivery miRNA inhibitors and chemotherapeutic compounds to enhance their efficacy.

How Leucocyte Cell Membrane Modified Janus Microcapsules are Phagocytosed by Cancer Cells

Modern drug delivery systems rely on either antibody-based single-surface recognition or on surface-hydrophobicity-based approaches. For a tumor showing various surface mutations, both approaches fail. This publication hereby presents Janus capsules based on polyelectrolyte multilayer microcapsules exhibiting human leucocyte (THP-1 cell line) cell membranes for discriminating HUVEC cells from three different cancer cell lines. Despite destroying the cellular integrity of leucocyte cells, the modified Janus capsules are able to adhere to cancer cells. Leucocyte cell-membrane-coated Janus capsules are phagocytosed with the cellular membrane part pointing to the cells.

Catalysis by multifunctional polyelectrolyte capsules

Gold and iron oxide modified polyelectrolyte capsules have been used as multifunctional platforms for catalysis and magnetic separation. Gold nanoparticle size and shell composition had an influence on their catalytic activity.