Towards theranostic multicompartment microcapsules: in-situ diagnostics and laser-induced treatment

Features of Anisotropic Drug Delivery Systems

Natural materials are anisotropic. Delivery systems occurring in nature, such as viruses, blood cells, pollen, and many others, do have anisotropy, while delivery systems made artificially are mostly isotropic. There is apparent complexity in engineering anisotropic particles or capsules with micron and submicron sizes. Nevertheless, some promising examples of how to fabricate particles with anisotropic shapes or having anisotropic chemical and/or physical properties are developed. Anisotropy of particles, once they face biological systems, influences their behavior. Internalization by the cells, flow in the bloodstream, biodistribution over organs and tissues, directed release, and toxicity of particles regardless of the same chemistry are all reported to be factors of anisotropy of delivery systems. Here, the current methods are reviewed to introduce anisotropy to particles or capsules, including loading with various therapeutic cargo, variable physical properties primarily by anisotropic magnetic properties, controlling directional motion, and making Janus particles. The advantages of combining different anisotropy in one entity for delivery and common problems and limitations for fabrication are under discussion.

Seeded RAFT Polymerization-Induced Self-assembly: Recent Advances and Future Opportunities

Over the past decade, polymerization-induced self-assembly (PISA) has fully proved its versatility for scale-up production of block copolymer nanoparticles with tunable sizes and morphologies; yet, there are still some limitations. Recently, seeded PISA approaches combing PISA with heterogeneous seeded polymerizations have been greatly explored and are expected to overcome the limitations of traditional PISA. In this review, recent advances in seeded PISA that have expanded new horizons for PISA are highlighted including i) general considerations for seeded PISA (e.g., kinetics, the preparation of seeds, the selection of monomers), ii) morphological evolution induced by seeded PISA (e.g., from corona-shell-core nanoparticles to vesicles, vesicles-to-toroid, disassembly of vesicles into nanospheres), and iii) various well-defined nanoparticles with hierarchical and sophisticated morphologies (e.g., multicompartment micelles, porous vesicles, framboidal vesicles, AXn -type colloidal molecules). Finally, new insights into seeded PISA and future perspectives are proposed.

A decade of developing applications exploiting the properties of polyelectrolyte multilayer capsules

Transferring the layer-by-layer (LbL) coating approach from planar surfaces to spherical templates and subsequently dissolving these templates leads to the fabrication of polyelectrolyte multilayer capsules. The versatility of the coatings of capsules and their flexibility upon bringing in virtually any material into the coatings has quickly drawn substantial attention. Here, we provide an overview of the main developments in this field, highlighting the trends in the last decade. In the beginning, various methods of encapsulation and release are discussed followed by a broad range of applications, which were developed and explored. We also outline the current trends, where the range of applications is continuing to grow, including addition of whole new and different application areas.

Nanoarchitectonics beyond perfect order - not quite perfect but quite useful

Nanoarchitectonics, like architectonics, allows the design and building of structures, but at the nanoscale. Unlike those in architectonics, and even macro-, micro-, and atomic-scale architectonics, the assembled structures at the nanoscale do not always follow the projected design. In fact, they do follow the projected design but only for self-assembly processes producing structures with perfect order. Here, we look at nanoarchitectonics allowing the building of nanostructures without a perfect arrangement of building blocks. Here, fabrication of structures from molecules, polymers, nanoparticles, and nanosheets to polymer brushes, layer-by-layer assembly structures, and hydrogels through self-assembly processes is discussed, where perfect order is not necessarily the aim to be achieved. Both planar substrate and spherical template-based assemblies are discussed, showing the challenging nature of research in this field and the usefulness of such structures for numerous applications, which are also discussed here.

Tailoring Polymer-Based Nanoassemblies for Stimuli-Responsive Theranostic Applications

Polymer assemblies on the nanoscale represent a powerful toolbox for the design of theranostic systems when combined with both therapeutic compounds and diagnostic reporting ones. Here, recent advances in the design of theranostic systems for various diseases, containing-in their architecture-either polymers or polymer assemblies as one of the building blocks are presented. This review encompasses the general principles of polymer self-assembly, from the production of adequate copolymers up to supramolecular assemblies with theranostic functionality. Such polymer nanoassemblies can be further tailored through the incorporation of inorganic nanoparticles to endow them with multifunctional therapeutic and/or diagnostic features. Systems that change their architecture or properties in the presence of stimuli are selected, as responsivity to changes in the environment is a key factor for enhancing efficiency. Such theranostic systems are based on the intrinsic properties of copolymers or one of the other components. In addition, systems with a more complex architecture, such as multicompartments, are presented. Selected systems indicate the advantages of such theranostic approaches and provide a basis for further developments in the field.

Immunogenic Cell Death and Role of Nanomaterials Serving as Therapeutic Vaccine for Personalized Cancer Immunotherapy

Immunogenic cell death (ICD) is a rapidly growing research area representing one of the emerging therapeutic strategies of cancer immunotherapy. ICD is an umbrella term covering several cell death modalities including apoptosis, necroptosis, ferroptosis and pyroptosis, and is the product of a balanced combination of adjuvanticity (damage-associated molecular patterns and chemokines/cytokines) and antigenicity (tumor associated antigens). Only a limited number of anti-cancer therapies are available to induce ICD in experimental cancer therapies and even much less is available for clinical use. To overcome this limitation, nanomaterials can be used to increase the immunogenicity of cancer cells killed by anti-cancer therapy, which in themselves are not necessarily immunogenic. In this review, we outline the current state of knowledge of ICD modalities and discuss achievements in using nanomaterials to increase the immunogenicity of dying cancer cells. The emerging trends in modulating the immunogenicity of dying cancer cells in experimental and translational cancer therapies and the challenges facing them are described. In conclusion, nanomaterials are expected to drive further progress in their use to increase efficacy of anti-cancer therapy based on ICD induction and in the future, it is necessary to validate these strategies in clinical settings, which will be a challenging research area.

Real-Time Temperature Monitoring of Photoinduced Cargo Release inside Living Cells Using Hybrid Capsules Decorated with Gold Nanoparticles and Fluorescent Nanodiamonds

Real-time temperature monitoring within biological objects is a key fundamental issue for understanding the heating process and performing remote-controlled release of bioactive compounds upon laser irradiation. The lack of accurate thermal control significantly limits the translation of optical laser techniques into nanomedicine. Here, we design and develop hybrid (complex) carriers based on multilayered capsules combined with nanodiamonds (NV centers) as nanothermometers and gold nanoparticles (Au NPs) as nanoheaters to estimate an effective laser-induced temperature rise required for capsule rupture and further release of cargo molecules outside and inside cancerous (B16-F10) cells. We integrate both elements (NV centers and Au NPs) in the capsule structure using two strategies: (i) loading inside the capsule's cavity (CORE) and incorporating them inside the capsule's wall (WALL). Theoretically and experimentally, we show the highest and lowest heat release from capsule samples (CORE or WALL) under laser irradiation depending on the Au NP arrangement within the capsule. Applying NV centers, we measure the local temperature of capsule rupture inside and outside the cells, which is determined to be 128 ± 1.12 °C. Finally, the developed hybrid containers can be used to perform the photoinduced release of cargo molecules with simultaneous real-time temperature monitoring inside the cells.

The acoustic radiation force on a multi-layered polymer capsule placed in a fluid-filled tube

Acoustic manipulation has a series of application in biomedicine, colloidal assembly, and chemistry. A three-layered polymer capsule is generally used structure in manipulation system because it has better protection to the core filled drug or compounds and possesses higher flexibility. In this paper, a theoretical model of acoustic radiation force acting on a three-layered drug capsule in a vessel is established. The acoustic radiation force on a capsule, which comprises of a drug core, a poly(lactide-co-glycolide) mid shell and a chitosan outer shell in the cylindrical tube filled with ideal fluid, is calculated using acoustic wave theory. The influences of the tube, the surrounding fluid and the geometric size of chitosan, poly(lactide-co-glycolide) shell and drug core on acoustic radiation force are investigated. The numerical simulations based on finite element method are introduced to compute the acoustic radiation force and compared with the analytical results. Moreover, the comparison among the capsule in impedance tube, in rigid tube and in unbounded space is obtained simulating specific environment. Simulation results show that the influences of the rigid tube on the acoustic radiation force of the capsule can be ignored when the capsule is much smaller than the radius of the tube. With the increase of the capsule radius, the acoustic radiation force of the capsule changes demonstrably with the frequency and the tube radius because of the influence of the reflective wave resulted from the inner surface of the tube. The properties of the surrounding fluid affect the position of the resonant peaks. Outer radius and mid layer radius have more effects on the acoustic radiation force, but the drug core radius almost exerts no effect on it. The study illustrates that the capsule can be manipulated by acoustic wave with the suitable selection for the outer or mid shell radii, and the selection of drug core radius is of more freedom in this process.

Biodegradable polyelectrolyte/magnetite capsules for MR imaging and magnetic targeting of tumors

Rationale: The tireless research for effective drug delivery approaches is prompted by poor target tissue penetration and limited selectivity against diseased cells. To overcome these issues, various nano- and micro-carriers have been developed so far, but some of them are characterized by slow degradation time, thus hampering repeated drug administrations. The aim of this study was to pursue a selective delivery of magnetic biodegradable polyelectrolyte capsules in a mouse breast cancer model, using an external magnetic field.

Methods: Four different kinds of magnetic polyelectrolyte capsules were fabricated via layer-by-layer assembly of biodegradable polymers on calcium carbonate templates. Magnetite nanoparticles were embedded either into the capsules' shell (sample S) or both into the shell and the inner volume of the capsules (samples C_nS, where n is the number of nanoparticle loading cycles). Samples were first characterized in terms of their relaxometric and photosedimentometric properties. In vitro magnetic resonance imaging (MRI) experiments, carried out on RAW 264.7 cells, allowed the selection of two lead samples that proceeded for the in vivo testing on a mouse breast cancer model. In the set of in vivo experiments, an external magnet was applied for 1 hour following the intravenous injection of the capsules to improve their delivery to tumor, and MRI scans were acquired at different time points post administration.

Results: All samples were considered non-cytotoxic as they provided more than 76% viability of RAW 264.7 cells upon 2 h incubation. Sample S appeared to be the most efficient in terms of T₂-MRI contrast, but the less sensitive to external magnet navigation, since no difference in MRI signal with and without the magnet was observed. On the other side, sample C₆S was efficiently delivered to the tumor tissue, with a three-fold T₂-MRI contrast enhancement upon the external magnet application. The effective magnetic targeting of C₆S capsules was also confirmed by the reduction in T₂-MRI contrast in spleen if compared with the untreated with magnet mice values, and the presence of dense and clustered iron aggregates in tumor histology sections even 48 h after the magnetic targeting.

Conclusion: The highlighted strategy of magnetic biodegradable polyelectrolyte capsules' design allows for the development of an efficient drug delivery system, which through an MRI-guided externally controlled navigation may lead to a significant improvement of the anticancer chemotherapy performance.

Robust Damage-Reporting Strategy Enabled by Dual-Compartment Microcapsules

Dye-filled microcapsules are an attractive way to identify microscopic damage of materials by the naked eye. However, there are many disadvantages in traditional microcapsule-based self-reporting materials, such as a poor self-reporting effect. A new concept for the design of self-reporting microcapsules is presented here. Our work develops a novel kind of dual-compartmental microcapsule via Pickering emulsion photopolymerization, which can encapsulate two interacting species ("pro-dye" and "developer") separately in a single microcapsule. In our strategy, SiO₂ microspheres encapsulating polyetheramine (PEA, developer) were first prepared and employed as a Pickering emulsifier to stabilize oil-in-water emulsions, in which the oil phase consisted of 2',7'-dichlorofluorescein (DCF, pro-dye) and a monomer. After the monomer polymerization, a dual-compartment microcapsule, which encapsulated the pro-dye in the core and the developer in the shell, was obtained. Upon the rupture of the microcapsule, the pro-dye and the developer were released simultaneously and reacted to yield a pronounced chromogenic response. Compared with traditional double-microcapsule systems, this dual-compartment microcapsule system demonstrated a more efficient and pronounced self-reporting effect. This is the first time that a double-encapsulation scheme involving the compartmentalized release of two interacting species within a single microcapsule has been demonstrated for self-reporting, which overcomes the tough problems of the uneven distribution of the traditional double-microcapsule systems.

Polyelectrolyte Multilayer Capsule (PEMC)-Based Scaffolds for Tissue Engineering

Tissue engineering (TE) is a highly multidisciplinary field that focuses on novel regenerative treatments and seeks to tackle problems relating to tissue growth both in vitro and in vivo. These issues currently involve the replacement and regeneration of defective tissues, as well as drug testing and other related bioapplications. The key approach in TE is to employ artificial structures (scaffolds) to support tissue development; these constructs should be capable of hosting, protecting and releasing bioactives that guide cellular behaviour. A straightforward approach to integrating bioactives into the scaffolds is discussed utilising polyelectrolyte multilayer capsules (PEMCs). Herein, this review illustrates the recent progress in the use of CaCO3 vaterite-templated PEMCs for the fabrication of functional scaffolds for TE applications, including bone TE as one of the main targets of PEMCs. Approaches for PEMC integration into scaffolds is addressed, taking into account the formulation, advantages, and disadvantages of such PEMCs, together with future perspectives of such architectures.

Dual Transport of Active Substances with a Layer-by-Layer-Based Drug Delivery System to Terminate Inflammatory Processes

Conventional therapies for chronic inflammation with high dose application of active agents are often accompanied with severe side effects so that other therapeutical strategies shall be developed to be less physically demanding but still highly efficient. Locally applied Layer-by-Layer (LbL) microcarriers transporting a low, but efficient dosage of active agents directly into the inflamed tissue offer a gentle therapy option. Here, the inhibition of highly degradative enzyme human neutrophile elastase (HNE) is adressed, which is produced and secreted by neutrophile granulocytes (PMNs) in the progress of inflammation. The protected transport and release of its natural inhibitor α1-antitrypsin (AT) as a constituent of the microcarrier's biopolymer multilayer allows for an efficient inhibition of extra- and intracellular elastase. The HOCl scavenger molecule cefoperazone, which preserves AT activity, as an additional multilayer constituent induces a much higher efficacy of the inhibitor. The successful assembly of both agents in different layers of the multilayer and the subsequent HNE inhibition in PMNs is investigated. The parallel application of cefoperazone leads to an enhanced inhibitory effect even with reduced AT amount and reduced carrier:cell ratio. It is demonstrated that the modular assembly strategy of LbL carriers allows for efficient synergistic effect of active agents in inflammatory process.

Liposomal nanotheranostics for multimode targeted in vivo bioimaging and near-infrared light mediated cancer therapy

Developing a nanotheranostic agent with better image resolution and high accumulation into solid tumor microenvironment is a challenging task. Herein, we established a light mediated phototriggered strategy for enhanced tumor accumulation of nanohybrids. A multifunctional liposome based nanotheranostics loaded with gold nanoparticles (AuNPs) and emissive graphene quantum dots (GQDs) were engineered named as NFGL. Further, doxorubicin hydrochloride was encapsulated in NFGL to exhibit phototriggered chemotherapy and functionalized with folic acid targeting ligands. Encapsulated agents showed imaging bimodality for in vivo tumor diagnosis due to their high contrast and emissive nature. Targeted NFGL nanohybrids demonstrated near infrared light (NIR, 750 nm) mediated tumor reduction because of generated heat and Reactive Oxygen Species (ROS). Moreover, NFGL nanohybrids exhibited remarkable ROS scavenging ability as compared to GQDs loaded liposomes validated by antitumor study. Hence, this approach and engineered system could open new direction for targeted imaging and cancer therapy.

Giant Polymer Compartments for Confined Reactions

In nature, various specific reactions only occur in spatially controlled environments. Cell compartment and subcompartments act as the support required to preserve the bio-specificity and functionality of the biological content, by affording absolute segregation. Inspired by this natural perfect behavior, bottom-up approaches are on focus to develop artificial cell-like structures, crucial for understanding relevant bioprocesses and interactions or to produce tailored solutions in the field of therapeutics and diagnostics. In this review, we discuss the benefits of constructing polymer-based single and multicompartments (capsules and giant unilamellar vesicles (GUVs)), equipped with biomolecules as to mimic cells. In this respect, we outline key examples of how such structures have been designed from scratch, namely, starting from the application-oriented selection and synthesis of the amphiphilic block copolymer. We then present the state-of-the-art techniques for assembling the supramolecular structure while permitting the encapsulation of active compounds and the incorporation of peptides/membrane proteins, essential to support in situ reactions, e.g., to replicate intracellular signaling cascades. Finally, we briefly discuss important features that these compartments offer and how they could be applied to engineer the next generation of microreactors, therapeutic solutions, and cell models.

Enhanced Uptake and Endosomal Release of LbL Microcarriers Functionalized with Reversible Fusion Proteins

The efficient application of smart drug-delivery systems requires further improvement of their cellular uptake and in particular their release from endolysosomal compartments into the cytoplasm of target cells. The usage of virus proteins allows for such developments, as viruses have evolved efficient entry mechanisms into the cell, mediated by their fusion proteins. In our investigations, the transferability of the glycoprotein G which is a fusion protein of the vesicular stomatitis virus (VSV-G) onto the surface of a layer-by-layer (LbL) designed microcarrier was investigated. The assembly of VSV-G as a reversible viral fusion protein onto LbL microcarriers indeed induced an enhanced uptake rate on Vero cells as well as a fast and efficient release of the intact carriers from endolysosomes into the cytoplasm. Additionally, neither virus-associated effects on cellular viability nor activation of an interferon response were detected. Our study emphasizes the suitability of VSV-G as an efficient surface functionalization of drug-delivery systems.

Classification of analytics, sensorics, and bioanalytics with polyelectrolyte multilayer capsules

Polyelectrolyte multilayer (PEM) capsules, constructed by LbL (layer-by-layer)-adsorbing polymers on sacrificial templates, have become important carriers due to multifunctionality of materials adsorbed on their surface or encapsulated into their interior. They have been also been used broadly used as analytical tools. Chronologically and traditionally, chemical analytics has been developed first, which has long been synonymous with all analytics. But it is not the only development. To the best of our knowledge, a summary of all advances including their classification is not available to date. Here, we classify analytics, sensorics, and biosensorics functionalities implemented with polyelectrolyte multilayer capsules and coated particles according to the respective stimuli and application areas. In this classification, three distinct categories are identified: (I) chemical analytics (pH; K⁺, Na⁺, and Pb²⁺ ion; oxygen; and hydrogen peroxide sensors and chemical sensing with surface-enhanced Raman scattering (SERS)); (II) physical sensorics (temperature, mechanical properties and forces, and osmotic pressure); and (III) biosensorics and bioanalytics (fluorescence, glucose, urea, and protease biosensing and theranostics). In addition to this classification, we discuss also principles of detection using the above-mentioned stimuli. These application areas are expected to grow further, but the classification provided here should help (a) to realize the wealth of already available analytical and bioanalytical tools developed with capsules using inputs of chemical, physical, and biological stimuli and (b) to position future developments in their respective fields according to employed stimuli and application areas. Graphical abstract.

Compound-Droplet-Pairs-Filled Hydrogel Microfiber for Electric-Field-Induced Selective Release

The separate co-encapsulation and selective controlled release of multiple encapsulants in a predetermined sequence has potentially important applications for drug delivery and tissue engineering. However, the selective controlled release of distinct contents upon one triggering event for most existing microcarriers still remains challenging. Here, novel microfluidic fabrication of compound-droplet-pairs-filled hydrogel microfibers (C-Fibers) is presented for two-step selective controlled release under AC electric field. The parallel arranged compound droplets enable the separate co-encapsulation of distinct contents in a single microfiber, and the release sequence is guaranteed by the discrepancy of the shell thickness or core conductivity of the encapsulated droplets. This is demonstrated by using a high-frequency electric field to trigger the first burst release of droplets with higher conductivity or thinner shell, followed by the second release of the other droplets under low-frequency electric field. The reported C-Fibers provide novel multidelivery system for a wide range of applications that require controlled release of multiple ingredients in a prescribed sequence.

Synthesis of Multicompartment Nanoparticles of ABC Miktoarm Star Polymers by Seeded RAFT Dispersion Polymerization

Polymeric multicompartment nanoparticles (MCNs) of μ-ABC miktoarm star polymers composed of poly(N,N-dimethylacrylamide) (PDMA), poly(butyl methacrylate) (PBMA), and polystyrene (PS) were synthesized by Cu(I)-catalyzed click reaction and seeded RAFT dispersion polymerization. The synthesized MCNs have a solvophobic PBMA core with separate segregated PS microdomains and a solvophilic PDMA corona. The size and/or morphology of MCNs are correlative to the length of PDMA, PBMA, and PS segments. Ascribed to the characteristic structure, MCNs of μ-DBS can decrease interfacial tension in n-hexane/water, which is much superior to linear diblock copolymer nanoassemblies.

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.

Safe and Effective Delivery of Antitumor Drug Using Mesenchymal Stem Cells Impregnated with Submicron Carriers

An important area in modern malignant tumor therapy is the optimization of antitumor drugs pharmacokinetics. The use of some antitumor drugs is limited in clinical practice due to their high toxicity. Therefore, the strategy for optimizing the drug pharmacokinetics focuses on the generation of high local concentrations of these drugs in the tumor area with minimal systemic and tissue-specific toxicity. This can be achieved by encapsulation of highly toxic antitumor drug (vincristine (VCR) that is 20-50 times more toxic than widely used the antitumor drug doxorubicin) into nano- and microcarriers with their further association into therapeutically relevant cells that possess the ability to migrate to sites of tumor. Here, we fundamentally examine the effect of drug carrier size on the behavior of human mesenchymal stem cells (hMSCs), including internalization efficiency, cytotoxicity, cell movement, to optimize the conditions for the development of carrier-hMSCs drug delivery platform. Using the malignant tumors derived from patients, we evaluated the capability of hMSCs associated with VCR-loaded carriers to target tumors using a three-dimensional spheroid model in collagen gel. Compared to free VCR, the developed hMSC-based drug delivery platform showed enhanced antitumor activity regarding those tumors that express CXCL12 (stromal cell-derived factor-1 (SDF-1)) gene, inducing directed migration of hMSCs via CXCL12 (SDF-1)/CXCR4 pathway. These results show that the combination of encapsulated antitumor drugs and hMSCs, which possess the properties of active migration into tumors, is therapeutically beneficial and demonstrated high efficiency and low systematic toxicity, revealing novel strategies for chemotherapy in the future.

Composite materials based on Ag nanoparticles in situ synthesized on the vaterite porous matrices

We have designed sensors based on Ag nanoparticles synthesized in situ on the vaterite beads. In this article we demonstrate an approach to produce size controllable spherical and elliptical vaterite particles and discuss time-dependent in situ Ag nanoparticles synthesis and its potential effect on surface-enhanced Raman scattering. The time dependent silver reduction synthesis in inorganic porous particles allows to regulate the number and size of Ag nanoparticles. It is shown that the irregular surface and high porosity of vaterite particles and large amount (surface filling factor) of the Ag nanoparticles are the critical parameters to increase the SERS signal to 10⁴ times. Such inorganic composites have a huge potential in medical applications; soon they provide an opportunity to study intracellular processes in vivo. The detailed characterization of the microstructure of these composites was studied by scanning and transmission electron microscopy, including 3D visualization and energy dispersive x-ray microanalysis.

Trojan-Horse-Like Stimuli-Responsive Microcapsules

Multicompartment microcapsules, with each compartment protected by a distinct stimuli-responsive shell for versatile controlled release, are highly desired for developing new-generation microcarriers. Although many multicompartmental microcapsules have been created, most cannot combine different release styles to achieve flexible programmed sequential release. Here, one-step template synthesis of controllable Trojan-horse-like stimuli-responsive microcapsules is reported with capsule-in-capsule structures from microfluidic quadruple emulsions for diverse programmed sequential release. The nested inner and outer capsule compartments can separately encapsulate different contents, while their two stimuli-responsive hydrogel shells can individually control the content release from each capsule compartment for versatile sequential release. This is demonstrated by using three types of Trojan-horse-like stimuli-responsive microcapsules, with different combinations of release styles for flexible programmed sequential release. The proposed microcapsules provide novel advanced candidates for developing new-generation microcarriers for diverse, efficient applications.

Large deformation electrohydrodynamics of a Skalak elastic capsule in AC electric field

The axisymmetric electrohydrodynamic deformation of an elastic capsule with a capacitive membrane obeying the Skalak law under a uniform AC electric field is investigated using analytical and boundary integral theory. The low capillary number (the ratio of destabilizing shear or electric force to the stabilizing elastic force) regime shows that time-averaged prolate and oblate spheroid deformations, and the time-periodic prolate-sphere, oblate-sphere breathing modes are commensurate with the time averaged-deformation. A novel prolate-oblate breathing mode is observed due to an interplay of finite membrane charging time and the field reversal of the AC field. The study, when extended to high capillary numbers, shows new breathing modes of cylinder-prolate, cylinder-oblate, and biconcave-prolate deformation. These are the results of highly compressive normal Maxwell stress at the poles and are aided by a weak compressive equatorial stress, characteristic of a capacitive membrane. The findings of this work should form the basis for the understanding of more complex biological cells and synthetic capsules for industrial applications.

Next-Generation Theranostic Agents Based on Polyelectrolyte Microcapsules Encoded with Semiconductor Nanocrystals: Development and Functional Characterization

Fabrication of polyelectrolyte microcapsules and their use as carriers of drugs, fluorescent labels, and metal nanoparticles is a promising approach to designing theranostic agents. Semiconductor quantum dots (QDs) are characterized by extremely high brightness and photostability that make them attractive fluorescent labels for visualization of intracellular penetration and delivery of such microcapsules. Here, we describe an approach to design, fabricate, and characterize physico-chemical and functional properties of polyelectrolyte microcapsules encoded with water-solubilized and stabilized with three-functional polyethylene glycol derivatives core/shell QDs. Developed microcapsules were characterized by dynamic light scattering, electrophoretic mobility, scanning electronic microscopy, and fluorescence and confocal microscopy approaches, providing exact data on their size distribution, surface charge, morphological, and optical characteristics. The fluorescence lifetimes of the QD-encoded microcapsules were also measured, and their dependence on time after preparation of the microcapsules was evaluated. The optimal content of QDs used for encoding procedure providing the optimal fluorescence properties of the encoded microcapsules was determined. Finally, the intracellular microcapsule uptake by murine macrophages was demonstrated, thus confirming the possibility of efficient use of developed system for live cell imaging and visualization of microcapsule transportation and delivery within the living cells.

Silver Alginate Hydrogel Micro- and Nanocontainers for Theranostics: Synthesis, Encapsulation, Remote Release, and Detection

We have designed multifunctional silver alginate hydrogel microcontainers referred to as loaded microcapsules with different sizes by assembling them via a template assisted approach using natural, highly porous calcium carbonate cores. Sodium alginate was immobilized into the pores of calcium carbonate particles of different sizes followed by cross-linking via addition of silver ions, which had a dual purpose: on one hand, the were used as a cross-linking agent, albeit in the monovalent form, while on the other hand they have led to formation of silver nanoparticles. Monovalent silver ions, an unusual cross-linking agent, improve the sensitivity to ultrasound, lead to homogeneous distribution of silver nanoparticles. Silver nanoparticles appeared on the shell of the alginate microcapsules in the twin-structure as determined by transmission electron microscopy. Remote release of a payload from alginate containers by ultrasound was found to strongly depend on the particle size. The possibility to use such particles as a platform for label-free molecule detection based on the surface enhanced Raman scattering was demonstrated. Cytotoxicity and cell uptake studies conducted in this work have revealed that microcontainers exhibit nonessential level of toxicity with an efficient uptake of cells. The above-described functionalities constitute building blocks of a theranostic system, where detection and remote release can be achieved with the same carrier.

Boosting the Peroxidase-Like Activity of Nanostructured Nickel by Inducing Its 3+ Oxidation State in LaNiO3 Perovskite and Its Application for Biomedical Assays

Catalytic nanomaterials with intrinsic enzyme-like activities, called nanozymes, have recently attracted significant research interest due to their unique advantages relative to natural enzymes and conventional artificial enzymes. Among the nanozymes developed, particular interests have been devoted to nanozymes with peroxidase mimicking activities because of their promising applications in biosensing, bioimaging, biomedicine, etc. Till now, lots of functional nanomaterials have been used to mimic peroxidase. However, few studies have focused on the Ni-based nanomaterials for peroxidase mimics. In this work, we obtained the porous LaNiO₃ nanocubes with high peroxidase-like activity by inducing its 3+ oxidation state in LaNiO₃ perovskite and optimizing the morphology of LaNiO₃ perovskite. The peroxidase mimicking activity of the porous LaNiO₃ nanocubes with Ni³⁺ was about 58~fold and 22~fold higher than that of NiO with Ni²⁺ and Ni nanoparticles with Ni⁰. More, the porous LaNiO₃ nanocubes exhibited about 2-fold higher activity when compared with LaNiO₃ nanoparticles. Based on the superior peroxidase-like activity of porous LaNiO₃ nanocubes, facile colorimetric assays for H₂O₂, glucose, and sarcosine detection were developed. Our present work not only demonstrates a useful strategy for modulating nanozymes' activities but also provides promising bioassays for clinical diagnostics.

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.

Anisotropic noble metal nanoparticles: Synthesis, surface functionalization and applications in biosensing, bioimaging, drug delivery and theranostics

Anisotropic nanoparticles have fascinated scientists and engineering communities for over a century because of their unique physical and chemical properties. In recent years, continuous advances in design and fabrication of anisotropic nanoparticles have opened new avenues for application in various areas of biology, chemistry and physics. Anisotropic nanoparticles have the plasmon absorption in the visible as well as near-infrared (NIR) region, which enables them to be used for crucial applications such as biological imaging, medical diagnostics and therapy ("theranostics"). Here, we describe the progress in anisotropic nanoparticles achieved since the millennium in the area of preparation including various shapes and modification of the particle surface, and in areas of application by providing examples of applications in biosensing, bio-imaging, drug delivery and theranostics. Furthermore, we also explain various mechanisms involved in cellular uptake of anisotropic nanoparticles, and conclude with our opinion on various obstacles that limit their applications in biomedical field.

STATEMENT OF SIGNIFICANCE

Anisotropy at the molecular level has always fascinated scientists and engineering communities for over a century, however, the research on novel methods through which shape and size of nanoparticles can be precisely controlled has opened new avenues for anisotropic nanoparticles in various areas of biology, chemistry and physics. In this manuscript, we describe progress achieved since the millennium in the areas of preparation of various shapes of anisotropic nanoparticles, investigate various methods involved in modifying the surface of these NPs, and provide examples of applications in biosensing and bio-imaging, drug delivery and theranostics. We also present mechanisms involved in cellular uptake of nanoparticles, describe different methods of preparation of anisotropic nanoparticles including biomimetic and photochemical synthesis, and conclude with our opinion on various obstacles that limit their applications in biomedical field.

Intracellular Microreactors as Artificial Organelles to Conduct Multiple Enzymatic Reactions Simultaneously

The creation of artificial organelles is a new paradigm in medical therapy that aims to substitute for missing cellular function by replenishing a specific cellular task. Artificial organelles tackle the challenge of mimicking metabolism, which is the set of chemical reactions that occur within a cell, mainly catalyzed by enzymes. So far, the few reported carriers able to conduct enzymatic reactions intracellularly are based on single-compartment carriers. However, cell organelles outperform by conducting multiple reactions simultaneously within confined sub-compartments. Here, the field of artificial organelles is advanced by reporting the assembly of a microreactor consisting of polymer capsules entrapping gold nanoclusters (AuNCs) and liposomes as sub-compartments. The fluorescence properties of AuNCs are employed to monitor the microreactors uptake by macrophages. Encapsulation is demonstrated and functionality of microreactors with trypsin (TRP) and horseradish peroxidase (HRP)-loaded liposomes is preserved. Multiple enzymatic reactions taking place simultaneously is demonstrated by exposing macrophages with the internalized microreactors to bis-(benzyloxycarbonyl-Ile-Pro-Arg)-Rho-110 and Amplex Red substrates, which are specific for TRP and HRP, respectively. Conversion of the substrates into the respective fluorescent products is observed. This report on the first microreactor conducting multiple enzymatic reactions simultaneously inside a cell is a considerable step in the field of artificial organelles.

Influence of Growth Characteristics of Induced Pluripotent Stem Cells on Their Uptake Efficiency for Layer-by-Layer Microcarriers

Induced pluripotent stem cells (iPSCs) have the ability to differentiate into any specialized somatic cell type, which makes them an attractive tool for a wide variety of scientific approaches, including regenerative medicine. However, their pluripotent state and their growth in compact colonies render them difficult to access and, therefore, restrict delivery of specific agents for cell manipulation. Thus, our investigation focus was set on the evaluation of the capability of layer-by-layer (LbL) designed microcarriers to serve as a potential drug delivery system to iPSCs, as they offer several appealing advantages. Most notably, these carriers allow for the transport of active agents in a protected environment and for a rather specific delivery through surface modifications. As we could show, charge and mode of LbL carrier application as well as the size of the iPSC colonies determine the interaction with and the uptake rate by iPSCs. None of the examined conditions had an influence on iPSC colony properties such as colony morphology and size or maintenance of pluripotent properties. An overall interaction rate of LbL carriers with iPSCs of up to 20% was achieved. Those data emphasize the applicability of LbL carriers for stem cell research. Additionally, the potential use of LbL carriers as a promising delivery tool for iPSCs was contrasted to viral particles and liposomes. The identified differences among those delivery tools have substantiated our major conclusion that LbL carrier uptake rate is influenced by characteristic features of the iPSC colonies (most notably colony size) in addition to their surface charges.

Design and characterization of microcapsules-integrated collagen matrixes as multifunctional three-dimensional scaffolds for soft tissue engineering

Three-dimensional (3D) porous scaffolds based on collagen are promising candidates for soft tissue engineering applications. The addition of stimuli-responsive carriers (nano- and microparticles) in the current approaches to tissue reconstruction and repair brings about novel challenges in the design and conception of carrier-integrated polymer scaffolds. In this study, a facile method was developed to functionalize 3D collagen porous scaffolds with biodegradable multilayer microcapsules. The effects of the capsule charge as well as the influence of the functionalization methods on the binding efficiency to the scaffolds were studied. It was found that the binding of cationic microcapsules was higher than that of anionic ones, and application of vacuum during scaffolds functionalization significantly hindered the attachment of the microcapsules to the collagen matrix. The physical properties of microcapsules-integrated scaffolds were compared to pristine scaffolds. The modified scaffolds showed swelling ratios, weight losses and mechanical properties similar to those of unmodified scaffolds. Finally, in vitro diffusional tests proved that the collagen scaffolds could stably retain the microcapsules over long incubation time in Tris-HCl buffer at 37°C without undergoing morphological changes, thus confirming their suitability for tissue engineering applications. The obtained results indicate that by tuning the charge of the microcapsules and by varying the fabrication conditions, collagen scaffolds patterned with high or low number of microcapsules can be obtained, and that the microcapsules-integrated scaffolds fully retain their original physical properties.

Biocompatible multilayer capsules engineered with a graphene oxide derivative: synthesis, characterization and cellular uptake

Graphene-based capsules have strong potential for a number of applications, including drug/gene delivery, tissue engineering, sensors, catalysis and reactors. The ability to integrate graphene into carrier systems with three-dimensional (3D) geometry may open new perspectives both for fundamental tests of graphene mechanics and for novel (bio)technological applications. However, the assembly of 3D complexes from graphene or its derivatives is challenging because of its poor stability under biological conditions. In this work, we attempted to integrate a layer of graphene oxide derivative into the shell of biodegradable capsules by exploiting a facile layer-by-layer (LbL) protocol. As a first step we optimized the LbL protocol to obtain colloidal suspensions of isolated capsules embedding the graphene oxide derivative. As a following step, we investigated in detail the morphological properties of the hybrid capsules, and how the graphene oxide derivative layer influences the porosity and the robustness of the multilayer composite shells. Finally, we verified the uptake of the capsules modified with the GO derivative by two cell lines and studied their intracellular localization and biocompatibility. As compared to pristine capsules, the graphene-modified capsules possess reduced porosity, reduced shell thickness and a higher stability against osmotic pressure. They show remarkable biocompatibility towards the tested cells and long-term colloidal stability and dispersion. By combining the excellent mechanical properties of a graphene oxide derivative with the high versatility of the LbL method, robust and flexible biocompatible polymeric capsules with novel characteristics have been fabricated.

Hollow Mesoporous Silica Nanocarriers with Multifunctional Capping Agents for In Vivo Cancer Imaging and Therapy

Efficient drug loading and selectivity in drug delivery are two key features of a good drug-carrier design. Here we report on such a drug carrier formed by using hollow mesoporous silica nanoparticles (HMS NPs) as the core and specifically designed multifunctional amphiphilic agents as the encapsulating shell. These nanocarriers combine the advantages of the HMS NP core (favorable physical and structural properties) and the versatility of an organic-based shell (e.g., specificity in chemical properties and modifiability). Moreover, both the properties of the core and the shell can be independently varied. The varied core and shell could then be integrated into a single device (drug carrier) to provide efficient and specific drug delivery. In vitro and in vivo data suggests that these drug nanocarriers are biocompatible and are able to deliver hydrophobic drugs selectively to target tumor cells. After the break of the pH-labile linkages in the shell, the drug payload can be released and the tumor cells are killed.

Alpha-2-macroglobulin loaded microcapsules enhance human leukocyte functions and innate immune response

Synthetic microstructures can be engineered to deliver bioactive compounds impacting on their pharmacokinetics and pharmacodynamics. Herein, we applied dextran-based layer-by-layer (LbL) microcapsules to deliver alpha-2-macroglobulin (α2MG), a protein with modulatory properties in inflammation. Extending recent observations made with dextran-microcapsules loaded with α2MG in experimental sepsis, we focused on the physical and chemical characteristics of these microstructures and determined their biology on rodent and human cells. We report an efficient encapsulation of α2MG into microcapsules, which enhanced i) human leukocyte recruitment to inflamed endothelium and ii) human macrophage phagocytosis: in both settings microcapsules were more effective than soluble α2MG or empty microcapsules (devoid of active protein). Translation of these findings revealed that intravenous administration of α2MG-microcapsules (but not empty microcapsules) promoted neutrophil migration into peritoneal exudates and augmented macrophage phagocytic functions, the latter response being associated with alteration of bioactive lipid mediators as assessed by mass spectrometry. The present study indicates that microencapsulation can be an effective strategy to harness the complex biology of α2MG with enhancing outcomes on fundamental processes of the innate immune response paving the way to potential future development in the control of sepsis.

Multifunctional nanocarriers for simultaneous encapsulation of hydrophobic and hydrophilic drugs in cancer treatment

Combination therapy for cancer patients is an important standard of care protocol because it can elicit synergistic therapeutic effects and reduce systemic toxicity by simultaneously modulating multiple cell-signaling pathways and overcoming multidrug resistance. Nanocarriers are expected to play a major role in delivering multiple drugs to tumor tissues by overcoming biological barriers. However, especially considering the different physical chemistry of chemotherapeutic drugs, it is highly desirable to develop a codelivery nanocarrier for controlled and targeted delivery of both hydrophobic and hydrophilic drugs. This review reports the recent developments in various combinational drug delivery systems and the simultaneous use of combinational drug delivery systems with functional agents.

Encapsulated enzymes with integrated fluorescence-control of enzymatic activity

Capsules filled with enzymes and fluorescence probes allow in situ enzymatic activity as well as kinetics on a single particle level to be monitored.

Pharmacological aspects of release from microcapsules - from polymeric multilayers to lipid membranes

This review is devoted to pharmacological applications of principles of release from capsules to overcome the membrane barrier. Many of these principles were developed in the context of polymeric multilayer capsule membrane modulation, but they are also pertinent to liposomes, polymersomes, capsosomes, particles, emulsion-based carriers and other carriers. We look at these methods from the physical, chemical or biological driving mechanisms point of view. In addition to applicability for carriers in drug delivery, these release methods are significant for another area directly related to pharmacology - modulation of the permeability of the membranes and thus promoting the action of drugs. Emerging technologies, including ionic current monitoring through a lipid membrane on a nanopore, are also highlighted.