Red blood cells and polyelectrolyte multilayer capsules: natural carriers versus polymer-based drug delivery vehicles

Natural products in osteoarthritis treatment: bridging basic research to clinical applications

Osteoarthritis (OA) is the most prevalent degenerative musculoskeletal disease, severely impacting the function of patients and potentially leading to disability, especially among the elderly population. Natural products (NPs), obtained from components or metabolites of plants, animals, microorganisms etc., have gained significant attention as important conservative treatments for various diseases. Recently, NPs have been well studied in preclinical and clinical researches, showing promising potential in the treatment of OA. In this review, we summed up the main signaling pathways affected by NPs in OA treatment, including NF-κB, MAPKs, PI3K/AKT, SIRT1, and other pathways, which are related to inflammation, anabolism and catabolism, and cell death. In addition, we described the therapeutic effects of NPs in different OA animal models and the current clinical studies in OA patients. At last, we discussed the potential research directions including in-depth analysis of the mechanisms and new application strategies of NPs for the OA treatment, so as to promote the basic research and clinical transformation in the future. We hope that this review may allow us to get a better understanding about the potential bioeffects and mechanisms of NPs in OA therapy, and ultimately improve the effectiveness of NPs-based clinical conservative treatment for OA patients.

Spontaneous shrinkage drives macromolecule encapsulation into layer-by-layer assembled biopolymer microgels

HYPOTHESIS

Recently, the anomalous shrinkage of surface-supported hyaluronate/poly-l-lysine (HA/PLL) microgels (µ-gels), which exceeds that reported for any other multilayer-based systems, has been reported [1]. The current study investigates the capability of these unique µ-gels for the encapsulation and retention of macromolecules, and proposes the shrinkage-driven assembly of biopolymer-based µ-gels as a novel tool for one-step surface biofunctionalization.

EXPERIMENTS

A set of dextrans (DEX) and their charged derivatives - carboxymethyl (CM)-DEX and diethylaminoethyl (DEAE)-DEX - has been utilized to evaluate the effects of macromolecular mass and net charge on µ-gel shrinkage and macromolecule entrapment. µ-gels formation on the surface of silicone catheters exemplifies their potential to tailor biointerfaces.

FINDINGS

Shrinkage-driven µ-gel formation strongly depends on the net charge and mass content of encapsulated macromolecules. Inclusion of neutral DEX decreases the degree of shrinkage several times, whilst charged DEXs adopt to the backbone of oppositely charged polyelectrolytes, resulting in shrinkage comparable to that of non-loaded µ-gels. Retention of CM-DEX in µ-gels is significantly higher compared to DEAE-DEX. These insights into the mechanisms of macromolecular entrapment into biopolymer-based µ-gels promotes fundamental understanding of molecular dynamics within the multilayer assemblies. Organization of biodegradable µ-gels at biomaterial surfaces opens avenues for their further exploitation in a diverse array of bioapplications.

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.

Hybrid Membrane-Derived Nanoparticles for Isoliquiritin Enhanced Glioma Therapy

Due to the obstruction and heterogeneity of the blood-brain barrier, the clinical treatment of glioma has been extremely difficult. Isoliquiritigenin (ISL) exhibits antitumor effects, but its low solubility and bioavailability limit its application potential. Herein, we established a nanoscale hybrid membrane-derived system composed of erythrocytes and tumor cells. By encapsulating ISL in hybrid membrane nanoparticles, ISL is expected to be enhanced for the targeting and long-circulation in gliomas therapy. We fused erythrocytes with human glioma cells U251 and extracted the fusion membrane via hypotension, termed as hybrid membrane (HM). HM-camouflaged ISL nanoparticles (ISL@HM NPs) were prepared and featured with FT-IR, SEM, TEM, and DLS particle analysis. As the results concluded, the ISL active pharmaceutical ingredients (APIs) were successfully encapsulated with HM membranes, and the NPs loading efficiency was 38.9 ± 2.99% under maximum entrapment efficiency. By comparing the IC50 of free ISL and NPs, we verified that the solubility and antitumor effect of NPs was markedly enhanced. We also investigated the mechanism of the antitumor effect of ISL@HM NPs, which revealed a marked inhibition of tumor cell proliferation and promotion of senescence and apoptosis of tumor cells of the formulation. In addition, the FSC and WB results examined the effects of different concentrations of ISL@HM NPs on tumor cell disruption and apoptotic protein expression. Finally, it can be concluded that hybridized membrane-derived nanoparticles could prominently increase the solubility of insoluble materials (as ISL), and also enhance its targeting and antitumor effect.

Load phycocyanin to achieve in vivo imaging of casein-porous starch microgels induced by ultra-high-pressure homogenization

Traditional bioactive substances are often limited in practical application due to their poor stability and low solubility. Therefore, it is imperative to develop biocompatible high loading microgel carriers. In this study, a novel type of casein-porous starch microgel was prepared under ultra-high-pressure homogenization, by using porous starch with the honeycomb three-dimensional network porous structure. Molecular interaction force analysis and thermodynamic analysis showed that electrostatic interaction played a major role in the formation of microgels. Circular dichroism and Fourier transform infrared spectroscopy showed that homogenization and pH were the main factors, which affected the formation and structural stability of microgels. Compared with casein-glutinous rice starch microgels, the encapsulation efficiency and loading capacity of phycocyanin in casein-porous starch microgels were increased by 77.27% and 135.10%, respectively. Thus, casein-porous starch microgels could not only achieve a sustained release effect, but also effectively transport phycocyanin to the gastrointestinal tract of zebrafish, while achieving good fluorescence imaging in vivo. Ultimately, the prepared casein-porous starch microgels could enrich the nanocarriers material, and contribute to the research of safe and effective fluorescent imaging materials.

Purification and erythrocyte-membrane perturbing activity of a ketose-specific lectin from Moringa oleifera seeds

This study purified a hemagglutinating protein (MoL) from Moringa oleifera seed, and investigated its hemolytic activity. Molecular weight and stability of MoL were also determined. Modification of some amino acid residues was carried out and the effect on MoL hemagglutinating activity determined. Other investigated parameters are the effects of temperature, concentration, incubation period, pH, and sugars on the protein's hemagglutinating and hemolytic activities. The native and subunit molecular weights were estimated as 30 and 27.5 kDa respectively. Hemagglutinating activity of MoL was slightly inhibited by fructose and sucrose, stable at temperature up to 90°C and within pH range of 2-4. Modification of tryptophan and arginine residues resulted in partial loss of hemagglutinating activity. The hemolytic activity of MoL was concentration, temperature, pH, and time-dependent. The study concluded that MoL showed hemolytic (membrane-perturbing) activity in moderate acidic conditions. This suggests its potential exploitation in improved intracellular delivery of bioactive compounds.

Cell-mediated targeting drugs delivery systems

Drug delivery systems have shown tremendous promise to improve the diagnostic and therapeutic effects of drugs due to their special property. Targeting tissue damage, tumors, or drugs with limited toxicity at the site of infection is the goal of successful pharmaceuticals. Targeted drug delivery has become significantly important in enhancing the pharmaceutical effects of drugs and reducing their side effects of therapeutics in the treatment of various disease conditions. Unfortunately, clinical translation of these targeted drug delivery system mechanisms faces many challenges. At present, only a few targeted drug delivery systems can achieve high targeting efficiency after intravenous injection, even though numerous surface markers and targeting approaches have been developed. Thus, cell-mediated drug-delivery targeting systems have received considerable attention for their enhanced therapeutic specificity and efficacy in the treatment of the disease. This review highlights the recent advances in the design of the different types of cells that have been explored for cell-mediated drug delivery and targeting mechanisms. A better understanding of cell biology orientation and a new generation of delivery strategies that utilize these endogenous approaches are expected to provide better solutions for specific site delivery and further facilitate clinical translation.

Design, synthesis and immunological evaluation of self-assembled antigenic peptides from dual-antigen targets: a broad-spectrum candidate for an effective antibreast cancer therapy

Background

Considering the narrow immune response spectrum of a single epitope, and the nanoparticles (NPs) as a novel adjuvant can achieve efficient delivery of antigenic peptides safely, a nano-system (denoted as DSPE-PEG-Man@EM-NPs) based on cathepsin B-responsive antigenic peptides was designed and synthesized.

Methods

Highly affinitive antigenic peptides were delivered by self-assembled NPs, and targeted erythrocyte membranes acted as a peptide carrier to improve antigenic peptides presentation and to strengthen cytotoxic T-cells reaction. Cathepsin B coupling could release antigenic peptides rapidly in dendritic cells.

Results

Evaluations showed that DSPE-PEG-Man@EM-NPs had obvious inhibitory effects towards both MCF-7 and MDA-MB-231 human breast cancer cell lines.

Conclusion

Overall, this strategy provides a novel strategy for boosting cytotoxic T lymphocytes response, thereby expanding the adaptation range of tumor antigenic peptides and improving the therapeutic effect of tumor immunotherapy with nanomedicine.

Immunocyte Membrane-Coated Nanoparticles for Cancer Immunotherapy

Despite the advances in surface bioconjugation of synthetic nanoparticles for targeted drug delivery, simple biological functionalization is still insufficient to replicate complex intercellular interactions naturally. Therefore, these foreign nanoparticles are inevitably exposed to the immune system, which results in phagocytosis by the reticuloendothelial system and thus, loss of their biological significance. Immunocyte membranes play a key role in intercellular interactions, and can protect foreign nanomaterials as a natural barrier. Therefore, biomimetic nanotechnology based on cell membranes has developed rapidly in recent years. This paper summarizes the development of immunocyte membrane-coated nanoparticles in the immunotherapy of tumors. We will introduce several immunocyte membrane-coated nanocarriers and review the challenges to their large-scale preparation and application.

Nanoparticles in Polyelectrolyte Multilayer Layer-by-Layer (LbL) Films and Capsules—Key Enabling Components of Hybrid Coatings

Originally regarded as auxiliary additives, nanoparticles have become important constituents of polyelectrolyte multilayers. They represent the key components to enhance mechanical properties, enable activation by laser light or ultrasound, construct anisotropic and multicompartment structures, and facilitate the development of novel sensors and movable particles. Here, we discuss an increasingly important role of inorganic nanoparticles in the layer-by-layer assembly—effectively leading to the construction of the so-called hybrid coatings. The principles of assembly are discussed together with the properties of nanoparticles and layer-by-layer polymeric assembly essential in building hybrid coatings. Applications and emerging trends in development of such novel materials are also identified.

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.

Advances in living cell-based anticancer therapeutics

This review summarizes recent advances in the applications of living cells as drug carriers or active drugs for anticancer drug delivery and cancer therapy.

Impact of Nanocapsules on Red Blood Cells Interplay Jointly Assessed by Optical Tweezers and Microscopy

In the framework of novel medical paradigm the red blood cells (RBCs) have a great potential to be used as drug delivery carriers. This approach requires an ultimate understanding of the peculiarities of mutual interaction of RBC influenced by nano-materials composed the drugs. Optical tweezers (OT) is widely used to explore mechanisms of cells' interaction with the ability to trap non-invasively, manipulate and displace living cells with a notably high accuracy. In the current study, the mutual interaction of RBC with polymeric nano-capsules (NCs) is investigated utilizing a two-channel OT system. The obtained results suggest that, in the presence of NCs, the RBC aggregation in plasma satisfies the 'cross-bridges' model. Complementarily, the allocation of NCs on the RBC membrane was observed by scanning electron microscopy (SEM), while for assessment of NCs-induced morphological changes the tests with the human mesenchymal stem cells (hMSC) was performed. The combined application of OT and advanced microscopy approaches brings new insights into the conception of direct observation of cells interaction influenced by NCs for the estimation of possible cytotoxic effects.

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.

Oxygen Self-Production Red Blood Cell Carrier System for MRI Mediated Cancer Therapy: Ferryl-Hb, Sonodynamic, and Chemical Therapy

Hypoxia in tumors can lead to insufficient oxygen supply during sonodynamic therapy (SDT), which in turn strengthens tumor resistance to sonodynamic efficacy. To conquer hypoxia in tumors and improve the treatment effectiveness, we developed oxygen self-production red blood cell (RBC) carrier system to decompose tumor endogenic H₂O₂ into O₂ and combine triplex cancer therapy: ferryl-hemoglobin (ferryl-Hb), sonodynamic, and chemical therapy. Both hydrophilic sonosensitizer and doxorubicin (DOX) were encapsulated inside RBCs (DOX/Mn-TPPS@RBCs). The drug release can be improved by combining the effects of H₂O₂ and ultrasonic irradiation. Here, we introduced a contrast agent, meso-tetra (4-sulfonatephenyl) porphyrinate manganese(III) complex (Mn-TPPS), which could be used to enhance the signal intensity of magnetic resonance imaging (MRI) of the tumor site. The feasibility of Mn-TPPS as a sonosensitizer was investigated during SDT. Importantly, DOX/Mn-TPPS@RBCs overcame hypoxia in the tumor and improved the efficacy of SDT owing to the O₂ generation by the catalase-catalyzed decomposition of tumor endogenic H₂O₂. Hemoglobin was simultaneously oxidized into highly oxidative ferryl-Hb species by H₂O₂ and reactive oxygen species, resulting in cytotoxicity. Overall, this drug delivery system is a promising therapeutic agent involving in situ production of oxygen inside the tumor, triplex therapy, and MRI.

Peptide-Functionalized Hydrogel Cubes for Active Tumor Cell Targeting

Conjugation of bioactive targeting molecules to nano- or micrometer-sized drug carriers is a pivotal strategy to improve their therapeutic efficiency. Herein, we developed pH- and redox-sensitive hydrogel particles with a surface-conjugated cancer cell targeting ligand for specific tumor-targeting and controlled release of the anticancer drug doxorubicin. The poly(methacrylic acid) (PMAA) hydrogel cubes of 700 nm and 2 μm with a hepsin-targeting (IPLVVPL) surface peptide are produced through multilayer polymer assembly on sacrificial cubical mesoporous cores. Direct peptide conjugation to the disulfide-stabilized hydrogels through a thiol-amine reaction does not compromise the structural integrity, hydrophilicity, stability in serum, or pH/redox sensitivity but does affect internalization by cancer cells. The cell uptake kinetics and the ultimate extent of internalization are controlled by the cell type and hydrogel size. The peptide modification significantly promotes the uptake of the 700 nm hydrogels by hepsin-positive MCF-7 cells due to ligand-receptor recognition but has a negligible effect on the uptake of 2 μm PMAA hydrogels. The selectivity of 700 nm IPLVVPL-PMAA hydrogel cubes to hepsin-overexpressing tumor cells is further confirmed by a 3-10-fold higher particle internalization by hepsin-positive MCF-7 and SK-OV-3 compared to that of hepsin-negative PC-3 cells. This work provides a facile method to fabricate enhanced tumor-targeting carriers of submicrometer size and improves the general understanding of particle design parameters for targeted drug delivery.

Bio-inspired drug delivery systems: an emerging platform for targeted cancer therapy

Bio-inspired platforms directly derived from biological sources are becoming a rapidly emerging field in the development of future anticancer therapeutics. The various platforms discussed are bacteria-based, virus-inspired, cell-derived, nanostructured lipid nanoparticles, and biomacromolecular drug delivery systems.

Photosensitizer Decorated Red Blood Cells as an Ultrasensitive Light-Responsive Drug Delivery System

Red blood cells (RBCs) have been widely explored as a natural drug delivery system (DDS) owing to their inherent biocompatibility and large internal cavities to load various types of functional molecules. Herein, we uncover that a photosensitizer, chlorin e6 (Ce6), could be decorated into the membrane of RBCs upon simple mixing, without affecting the membrane integrity and stability in dark. Upon light irradiation with a rather low power density, the singlet oxygen generated by Ce6 would lead to rather efficient disruption of RBC membrane. With doxorubicin (DOX), a typical chemotherapy drug, as the model, we engineer a unique type of light-responsive RBC-based DDS by decorating Ce6 on the cell membrane and loading DOX inside cells. The light triggered cell membrane breakdown would thus trigger instant release of DOX, enabling light-controlled chemotherapy with great specificity. Beyond that our RBC system could also be utilized for loading of larger biomolecules such as enzymes, whose release as well as catalytic function is also controlled by light. Our work thus presents a unique type of biocompatible cell-based DDS that can be precisely controlled by mild external stimuli, promising not only for cancer therapy but also for other potential applications in biotechnologies.

Solid surface vs. liquid surface: nanoarchitectonics, molecular machines, and DNA origami

Comparisons of science and technology between these solid and liquid surfaces would be a good navigation for current-to-future developments.

Co-Assembly of Heparin and Polypeptide Hybrid Nanoparticles for Biomimetic Delivery and Anti-Thrombus Therapy

Biomimetic delivery carriers using polypeptide/heparin hybrid nanoparticles that are adsorbed onto red blood cells for extended blood circulation time have been developed. This might open up an avenue to promote the innovations and advances of biomimetic, stimuli-responsive drug delivery, especially for the site-specific treatment of intravascular diseases such as thrombosis.

Intracellular redox induced drug release in cancerous and mesenchymal stem cells

In this report, we investigated intracellular redox induced drug release in cancerous cells and human mesenchymal stem cells (MSCs) as an example of healthy cells using redox-responsive microcapsules with covalently bonded anti-cancer drug (doxorubicin) via the amine-reactive cross-linker, 3,3'-dithiobis(sulfosuccinimidyl propionate) containing disulfide bond. Such rationally designed capsules with incorporated redox-sensitive cross-linker are capable of controllable Dox release in the presence of glutathione (GSH) due to a thiol-cleavable disulfide bonds. The treatment of human MSCs and human cervical cancer cell line (HeLa) with Dox-conjugated capsules showed that the Dox release was observed only when capsules incubated with HeLa cells which can be induced by high GSH level in cancerous (HeLa) cells. Moreover, the results of cell viability indicated that Dox-conjugated capsules are more effective when inducing cell death of HeLa than free Dox improving the anti-tumor efficacy of chemotherapeutic drug and simultaneously they possess lower cytotoxicity against MSCs compared to cancerous cells. Such properties are important in design of smart drug carriers for efficient cancer therapy.

Effect of Gaussian curvature modulus on the shape of deformed hollow spherical objects

A popular description of soft membranes uses the surface curvature energy introduced by Helfrich, which includes a spontaneous curvature parameter. In this paper we show how the Helfrich formula can also be of interest for a wider class of spherical elastic surfaces, namely with shear elasticity, and likely to model other deformable hollow objects. The key point is that when a stress-free state with spherical symmetry exists before subsequent deformation, its straightforwardly determined curvature ("geometrical spontaneous curvature") differs most of the time from the Helfrich spontaneous curvature parameter that should be considered in order to have the model being correctly used. Using the geometrical curvature in a set of independent parameters unveils the role of the Gaussian curvature modulus, which appears to play on the shape of an elastic surface even though this latter is closed, contrary to what happens for surfaces without spontaneous curvature. In appendices, clues are given to apply this alternative and convenient formulation of the elastic surface model to the particular case of thin spherical shells of isotropic material (TSSIMs).

Erythrocytes in nanomedicine: an optimal blend of natural and synthetic materials

A hybrid approach strategy using synthetic nanoparticles and erythrocytes offers an optimal blend of natural and synthetic materials. The combined advantages of erythrocytes and nanoparticles could serve as an immune-evasive multifunctional platform. This review summarized the research on state-of-the-art and significant advances in erythrocytes for nanomedicine, and presented are their fabrication process, their unique properties and applications. According to its structure, this review mainly focuses on three kinds of erythrocyte-based nanomedicine: whole erythrocytes as carriers, cell membrane coated nanoparticles, and nanoerythrosomes. In addition, some future prospects are also prudentially addressed. We expect rapid success in the advancement of erythrocyte-based nanomedicines, from the bench to the bedside.

In vitro and in vivo MRI visualization of nanocomposite biodegradable microcapsules with tunable contrast

Tunable MRI contrast of microcapsules was obtained.

Impact of high-frequency ultrasound on nanocomposite microcapsules: in silico and in situ visualization

Simulation and direct visualization of high-frequency (1.2 MHz) ultrasound impact on microcapsules with ZnO nanoparticles embedded in the shell.

Cell or cell membrane-based drug delivery systems

Natural cells have been explored as drug carriers for a long period. They have received growing interest as a promising drug delivery system (DDS) until recently along with the development of biology and medical science. The synthetic materials, either organic or inorganic, are found to be with more or less immunogenicity and/or toxicity. The cells and extracellular vesicles (EVs), are endogenous and thought to be much safer and friendlier. Furthermore, in view of their host attributes, they may achieve different biological effects and/or targeting specificity, which can meet the needs of personalized medicine as the next generation of DDS. In this review, we summarized the recent progress in cell or cell membrane-based DDS and their fabrication processes, unique properties and applications, including the whole cells, EVs and cell membrane coated nanoparticles. We expect the continuing development of this cell or cell membrane-based DDS will promote their clinic applications.

Turning erythrocytes into functional micromotors

Attempts to apply artificial nano/micromotors for diverse biomedical applications have inspired a variety of strategies for designing motors with diverse propulsion mechanisms and functions. However, existing artificial motors are made exclusively of synthetic materials, which are subject to serious immune attack and clearance upon entering the bloodstream. Herein we report an elegant approach that turns natural red blood cells (RBCs) into functional micromotors with the aid of ultrasound propulsion and magnetic guidance. Iron oxide nanoparticles are loaded into the RBCs, where their asymmetric distribution within the cells results in a net magnetization, thus enabling magnetic alignment and guidance under acoustic propulsion. The RBC motors display efficient guided and prolonged propulsion in various biological fluids, including undiluted whole blood. The stability and functionality of the RBC motors, as well as the tolerability of regular RBCs to the ultrasound operation, are carefully examined. Since the RBC motors preserve the biological and structural features of regular RBCs, these motors possess a wide range of antigenic, transport, and mechanical properties that common synthetic motors cannot achieve and thus hold considerable promise for a number of practical biomedical uses.

Advances in Anticancer Protein Delivery Using Micro-/ Nanoparticles

Proteins exhibiting anticancer activities, especially those capable of discriminately killing cancer cells, have attracted increasing interest in developing protein-based anticancer therapeutics. This progress report surveys recent advances in delivering anticancer proteins directly to tumor tissue for inducing apoptosis/necrosis or indirectly to antigen presenting cells for provoking immune responses. Protein delivery carriers such as inorganic particles, lipid particles, polymeric particles, DNA/protein based biomacromolecular particles as well as cell based carriers are reviewed with comments on their advantages and limitations. Future challenges and opportunities are also discussed.

Multifunctional theranostic red blood cells for magnetic-field-enhanced in vivo combination therapy of cancer

Red blood cells are attached to iron oxide nanoparticles pre-coated with chlorine e6, a photosensitizer, and then loaded with a chemotherapeutic drug, doxorubicin, to enable imaging-guided combined photodynamic and chemotherapy of cancer, achieving excellent synergistic therapeutic effects in an animal tumor model. This work highlights the great promise of integrating cell-based drug-delivery systems with nanotechnology as a biocompatible multifunctional platform for applications in cancer theranostics.

Macrophage depletion by free bisphosphonates and zoledronate-loaded red blood cells

Bisphosphonates, besides being important drugs for the treatment of various bone diseases, could also be used to induce apoptosis in macrophage-like and cancer cells. However, their activity in vivo is limited by a short plasma half-life and rapid uptake within bone. Therefore, several delivery systems have been proposed to modify their pharmacokinetic profile and biodistribution. Among these, red blood cells (RBCs) represent one of the most promising biological carriers. The aim of this study was to select the best performing compound among Clodronate, Pamidronate, Ibandronate and Zoledronate in killing macrophages and to investigate RBCs as innovative carrier system to selectively target bisphosphonates to macrophages. To this end, the encapsulation of the selected bisphosphonates in autologous RBCs as well as the effect on macrophages, both in vitro and in vivo were studied. This work shows that, among the tested bisphosphonates, Zoledronate has proven to be the most active molecule. Human and murine RBCs have been successfully loaded with Zoledronate by a procedure of hypotonic dialysis and isotonic resealing, obtaining a dose-dependent drug entrapment with a maximal loading of 7.96±2.03, 6.95±3.9 and 7.0±1.89 µmoles of Zoledronate/ml of packed RBCs for human, Swiss and Balb/C murine RBCs, respectively. Engineered RBCs were able to detach human and murine macrophages in vitro, leading to a detachment of 66±8%, 67±8% and 60.5±3.5% for human, Swiss and Balb/C RBCs, respectively. The in vivo efficacy of loaded RBCs was tested in Balb/C mice administering 59 µg/mouse of RBC-encapsulated Zoledronate. By a single administration, depletion of 29.0±16.38% hepatic macrophages and of 67.84±5.48% spleen macrophages was obtained, confirming the ability of encapsulated Zoledronate to deplete macrophages in vivo. In conclusion, RBCs loaded with Zoledronate should be considered a suitable system for targeted delivery to macrophages, both in vitro and in vivo.

Erythrocytes-based synthetic delivery systems: transition from conventional to novel engineering strategies

INTRODUCTION

Erythrocytes (red blood cells [RBCs]) and artificial or synthetic delivery systems such as liposomes, nanoparticles (NPs) are the most investigated carrier systems. Herein, progress made from conventional approach of using RBC as delivery systems to novel approach of using synthetic delivery systems based on RBC properties will be reviewed.

AREAS COVERED

We aim to highlight both conventional and novel approaches of using RBCs as potential carrier system. Conventional approaches which include two main strategies are: i) directly loading therapeutic moieties in RBCs; and ii) coupling them with RBCs whereas novel approaches exploit structural, mechanical and biological properties of RBCs to design synthetic delivery systems through various engineering strategies. Initial attempts included coupling of antibodies to liposomes to specifically target RBCs. Knowledge obtained from several studies led to the development of RBC membrane derived liposomes (nanoerythrosomes), inspiring future application of RBC or its structural features in other attractive delivery systems (hydrogels, filomicelles, microcapsules, micro- and NPs) for even greater potential.

EXPERT OPINION

In conclusion, this review dwells upon comparative analysis of various conventional and novel engineering strategies in developing RBC based drug delivery systems, diversifying their applications in arena of drug delivery. Regardless of the challenges in front of us, RBC based delivery systems offer an exciting approach of exploiting biological entities in a multitude of medical applications.

Endocytic pH-triggered degradation of nanoengineered multilayer capsules

The synthesis of cross-linker free layer-by-layer (LbL) capsules that solely utilize cellular pH variations as a trigger to specifically deconstruct and subsequently release cargo in cells is reported. These capsules demonstrate retention of water-soluble therapeutic molecules as small as 500 Da at extracellular pH. Triggered capsule degradation and release of cargo is observed within 30 min of cell uptake.

Insights into hydrophobic molecule release from polyelectrolyte multilayer films using in situ and ex situ techniques

Incorporation of hydrophobic curcumin (yellow discs) into a polyelectrolyte multilayer made from PDADMAC and PSS requires the use of water : ethanol solution. Release from the multilayer only occurs if the multilayer is dried prior to immersion in the electrolyte release solution.

Edible polyelectrolyte microcapsules with water-soluble cargo assembled in organic phase

Using "Generally Recognized as Safe" (GRAS) materials for assembly, edible polyelectrolytes (EPL/PGA) are coated on sugar (maltotriose)–dextran particles and crosslinked (left). Cargo-loaded hollow capsules are created by dissolution of the sugar template (right).

Bioinspired nanoarchitectonics as emerging drug delivery systems

Bioinspired nanoarchitectonics opens a new era for designing drug delivery systems.

Red blood cells decorated with functionalized core-shell magnetic nanoparticles: elucidation of the adsorption mechanism

The decoration of red blood cells (RBCs) with aminated and carboxylated core-shell magnetic nanoparticles (CSMNs) was studied and elucidated. It was demonstrated that only aminated CSMNs could decorate the RBCs and their adsorption interaction is mainly ruled by electrostatic attraction between the positively charged amino groups on CSMNs and the abundant sialic acid groups on the outer surface of RBCs.

Cell experimental studies on sonoporation: state of the art and remaining problems

Sonoporation is the formation of transient pores on cell membrane by ultrasound exposure. Sonoporation can be applied to the increasing delivery of drug or gene into cells. However, there are some problems encountered in sonoporation studies. The mechanisms to produce sonoporation are very complicated; there are too many experimental parameters affecting the sonoporation results; and there are many bio-effects accompanied with sonoporation. In the article, the cell experimental studies on sonoporation were sorted, including experimental methods, mechanisms to produce sonoporation, correlations between sonoporation experimental parameters and results, and bioeffects accompanied with sonoporation. We'd like to make the concepts about sonoporation clearer. The sonoporation technology may be a promising auxiliary technology to promote drug or gene therapy in the future.

25th anniversary article: Dynamic interfaces for responsive encapsulation systems

Encapsulation systems are urgently needed both as micrometer and sub-micrometer capsules for active chemicals' delivery, to encapsulate biological objects and capsules immobilized on surfaces for a wide variety of advanced applications. Methods for encapsulation, prolonged storage and controllable release are discussed in this review. Formation of stimuli responsive systems via layer-by-layer (LbL) assembly, as well as via mobile chemical bonding (hydrogen bonds, chemisorptions) and formation of special dynamic stoppers are presented. The most essential advances of the systems presented are multifunctionality and responsiveness to a multitude of stimuli - the possibility of formation of multi-modal systems. Specific examples of advanced applications - drug delivery, diagnostics, tissue engineering, lab-on-chip and organ-on-chip, bio-sensors, membranes, templates for synthesis, optical systems, and antifouling, self-healing materials and coatings - are provided. Finally, we try to outline emerging developments.

Human erythrocytes as drug carriers: loading efficiency and side effects of hypotonic dialysis, chlorpromazine treatment and fusion with liposomes

Human red blood cells (RBCs) are emerging as a highly biocompatible microparticulate drug delivery system. So far, drugs have commonly been loaded into freshly isolated RBCs using rather disruptive methods based on hypotonic shock, and assessment of damage was restricted to hemolysis. Here, we investigated loading of RBCs from blood bank units with enzymes of various molecular weights using hypotonic dialysis (HD), pretreatment with chlorpromazine (CPZ) and fusion with liposomes. The latter two techniques have received little attention in RBC loading so far. Along with loading efficiency, all methods were tested for the induction of side effects. Very importantly, next to hemolysis, we also addressed morphological changes and phosphatidyl serine (PS) exposure, which has been recognized as a critical parameter associated with premature RBC removal and induction of transfusion-related pathologies. The efficiency of loading using hypotonic dialysis decreased with the molecular weight of the enzyme. For liposomes and chlorpromazine, loading efficiencies were higher and independent of enzyme molecular weights. While hypotonic dialysis always induced a high degree of hemolysis, irreversible modifications in the morphology of the cells and PS exposure, the side effects that were induced by loading using CPZ and liposomes were limited. In particular, PS exposure, although high immediately after treatment, returned to physiological levels after recovery. Retention and deformability studies using a spleen-mimicking device showed that RBCs treated with CPZ and liposomes behave like physiological RBCs, while HD led to very fragile and poorly deformable RBCs.

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

Paving the way towards the application of polyelectrolyte multilayer capsules in theranostics, we describe diagnostic multi-functionality and drug delivery using multicompartment polymeric capsules which represent the next generation of drug delivery carriers. Their versatility is particularly important for potential applications in the area of theranostics wherein the carriers are endowed with the functionality for both diagnostics and therapy. Responsiveness towards external stimuli is attractive for providing controlled and on-demand release of encapsulated materials. An overview of external stimuli is presented with an emphasis on light as a physical stimulus which has been widely used for activation of microcapsules and release of their contents. In this article we also describe existing and new approaches to build multicompartment microcapsules as well as means available to achieve controlled and triggered release from their subcompartments, with a focus on applications in theranostics. Outlook for future directions in the area are highlighted.

Drug delivery carriers on the fringes: natural red blood cells versus synthetic multilayered capsules

Red blood cells (RBC) and synthetic multilayered nanocarriers may appear as distant 'extremes' of the continuum of diverse drug delivery systems. The former are natural, old and simple, whereas the latter are artificial, novel and sophisticated. However, juxtaposition of features of these types of carriers, offered in a review article published in this issue, is instructive. Such an analysis helps to define both their distinctions and similarities (structural, functional, technological, specific areas of utility), and illustrates perspectives of their translation into the practice. Thus, synthetic multilayered carriers (which, in some embodiments, use elements of design inspired by RBC) represent an attractive research object offering high degree of control of their features. These carriers may find utility for intracellular delivery, controlled release of multiple cargoes and imaging. On the other hand, RBC provide arguably the most attractive carriers for sustained intravascular delivery of variety of drugs including biotherapeutics, either encapsulated into the inner RBC volume or coupled to RBC surface. The discussion of specific medical utility of these carriers and comparative analysis of the factors that may affect their translation (including complexity, costs, market value and therapeutic benefit/risk ratio) is timely and likely to intensify in the near future.