Protamine Assembled in Multilayers on Colloidal Particles Can Be Exchanged and Released

Destruction of Polyelectrolyte Microcapsules Formed on CaCO3 Microparticles and the Release of a Protein Included by the Adsorption Method

The degradation of polyelectrolyte microcapsules formed on protein-free CaCO₃ particles consisting of polyallylamine (PAH) and polystyrene sulfonate (PSS) and the resulting yield of protein in the presence of various salts of different concentrations, as well as at two pH values, was studied by fluorescence spectroscopy; the protein was incorporated into prepared microcapsules by adsorption. It was found that a high concentration of sodium chloride (2 M) leads to considerable dissociation of PAH, which is apparently due to the loosening of polyelectrolytes under the action of ionic strength. At the same time, 0.2 M sodium chloride and ammonium sulfate of the same ionic strength (0.1 M) exert less influence on the amount of dissociated polymer. In the case of ammonium sulfate (0.1 M), the effect is due to the competitive binding of sulfate anions to the amino groups of the polyelectrolyte. However, unlike microcapsules formed on CaCO₃ particles containing protein, the dissociation of polyelectrolyte from microcapsules formed on protein-free particles increased with increasing temperature. Apparently, a similar effect is associated with the absence of a distinct shell, which was observed on microcapsules formed on protein-containing CaCO₃ particles. The high level of the presence of Fluorescein isothiocyanate (FITC)-labeled Bovine Serum Albumin (BSA) in the supernatant is explained by the large amount of electrostatically bound protein and the absence of a shell that prevents the release of the protein from the microcapsules. In 2M NaCl, during the observation period, the amount of the released protein did not exceed 70% of the total protein content in the capsules, in control samples, this value does not exceed 8%, which indicates the predominantly electrostatic nature of protein retention in capsules formed on protein-free CaCO₃ particles. The increase in protein yield and peeling of PAH with increasing pH is explained by the proximity of pH 7 to the point of charge exchange of the amino group of polyelectrolyte, as a result of the dissociation of the microcapsule.

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.

Sonication-Assisted Layer-by-Layer Assembly for Low Solubility Drug Nanoformulation

Sonication-assisted layer-by-layer (LbL) self-assembly is a nanoencapsulation technique based on the alternate adsorption of oppositely charged polyelectrolytes, enabling the encapsulation of low solubility drugs. In this work, a top-down LbL technique was performed using a washless approach and ibuprofen (IBF) as a model class II drug. For each saturated layer deposition, polyelectrolyte concentration was determined by titration curves. The first layer was constituted by cationic poly(allylamine hydrochloride) (PAH), given the IBF negative surface charge, followed by anionic polystyrenesulfonate (PSS). This polyelectrolyte sequence was made up with 2.5, 5.5, and 7.5 bilayer nanoshells. IBF nanoparticles (NPs) coated with 7.5 bilayers of PAH/PSS showed 127.5 ± 38.0 nm of particle size, a PDI of 0.24, and a high zeta potential (+32.7 ± 0.6 mV), allowing for a stable aqueous nanocolloid of the drug. IBF entrapment efficiency of 72.1 ± 5.8% was determined by HPLC quantification. In vitro MTT assay showed that LbL NPs were biocompatible. According to the number of coating layers, a controlled release of IBF from LbL NPs was achieved under simulated intestinal conditions (from 5 h up to 7 days). PAH/PSS-LbL NPs constitute a potential delivery system to improve biopharmaceutical parameters of water low solubility drugs.

Quantitative fluorescent profiling of VEGFRs reveals tumor cell and endothelial cell heterogeneity in breast cancer xenografts

Plasma membrane-localized vascular endothelial growth factor receptors (VEGFR) play a critical role in transducing VEGF signaling toward pro and antiangiogenic outcomes and quantitative characterization of these receptors is critical toward identifying biomarkers for antiangiogenic therapies, understanding mechanisms of action of antiangiogenic drugs, and advancing predictive computational models. While in vitro analysis of cell surface-VEGFRs has been performed, little is known about the levels of cell surface-VEGFR on tumor cells. Therefore, we inoculate nude mice with the human triple-negative breast cancer, MDA-MB-231, cell line; isolate human tumor cells and mouse tumor endothelial cells from xenografts; and quantitatively characterize the VEGFR localization on these cells. We observe 15,000 surface-VEGFR1/tumor endothelial cell versus 8200 surface-VEGFR1/tumor endothelial cell at 3 and 6 weeks of tumor growth, respectively; and we quantify 1200-1700 surface-VEGFR2/tumor endothelial cell. The tumor cell levels of VEGFR1 and VEGFR2 are relatively constant between 3 and 6 weeks: 2000-2200 surface-VEGFR1/tumor cell and ~1000 surface-VEGFR2/tumor cell. Cell-by-cell analysis provides additional insight into tumor heterogeneity by identifying four cellular subpopulations based on size and levels of cell membrane-localized VEGFR. Furthermore, when these ex vivo data are compared to in vitro data, we observe little to no VEGFRs on MDA-MB-231 cells, and the MDA-MB-231 VEGFR surface levels are not regulated by a saturating dose of VEGF. Overall, the quantification of these dissimilarities for the first time in tumor provides insight into the balance of modulatory (VEGFR1) and proangiogenic (VEGFR2) receptors.

Bio-inspired encapsulation and functionalization of living cells with artificial shells

In nature, most single cells do not have structured shells to provide extensive protection apart from diatoms and radiolarians. Fabrication of biomimetic structures based on living cells encapsulated with artificial shells has a great impact on the area of cell-based sensors and devices as well as fundamental studies in cell biology. The past decade has witnessed a rapid increase of research concerning the new fabrication strategies, functionalization and applications of this kind of encapsulated cells. In this review, the latest fabrication strategies on how to encapsulate living cells with functional shells based on the diversity of artificial shells are discussed: hydrogel matrix shells, sol-gel shells, polymeric shells, and induced mineral shells. Classical different types of artificial shells are introduced and their advantages and disadvantages are compared and explained. The biomedical applications of encapsulated cells with particular emphasis on cell implant protection, cell separation, biosensors, cell therapy and tissue engineering are also described and a recap of this review and the future perspectives on these active areas is given finally.

Inhibition of human neutrophil elastase by α1-antitrypsin functionalized colloidal microcarriers

Layer-by-layer (LbL)-coated microcarriers offer a good opportunity as transport systems for active agents into specific cells and tissues. The assembling of oppositely charged polyelectrolytes enables a modular construction of the carriers and therefore an optimized integration and application of drug molecules. Here, we report the multilayer incorporation and transport of α(1)-antitrypsin (AT) by colloidal microcarriers. AT is an anti-inflammatory agent and shows inhibitory effects toward its pro-inflammatory antagonist, human neutrophil elastase (HNE). The highly proteolytic enzyme HNE is released by polymorphonuclear leukocytes (PMNs) during inflammatory processes and can cause host tissue destruction and pain. The high potential of this study is based on a simultaneous intra- and extracellular application of AT-functionalized LbL carriers. Carrier application in PMNs results in significant HNE inhibition within 21 h. Microcarriers phagocytosed by PMNs were time dependently decomposed inside phagolysosomes, which enables the step-by-step release of AT. Here, AT inactivates HNE before being released, which avoids a further HNE concentration increase in the extracellular space and, subsequently, reduces the risk of further tissue destruction. Additionally, AT surface-functionalized microcarriers allow the inhibition of already released HNE in the extracellular space. Finally, this study demonstrates the successful application of LbL carriers for a concurrent extra- and intracellular HNE inhibition aiming the rebalancing of protease and antiprotease concentrations and the subsequent termination of chronic inflammations.

Influence of layer-by-layer (LbL) assembled CaCO(3)-carriers on macrophage signaling cascades

Numerous drawbacks in the current medical treatment of chronic inflammations still require the design of sensitive and gentle methods without side effects. Layer-by-layer (LbL) coated microcarriers loaded with a cocktail of anti-inflammatory substances are supposed to be a new challenge for the medical treatment of immunoreactive cells such as macrophages and polymorphonuclear leukocytes (PMN). Nevertheless, microcarrier application requires biocompatibility of the system itself. Therefore, the aim of this study was to investigate microcarrier CaCO(3) systems LbL coated with biopolymers and a lipid bilayer, respectively, regarding the maintenance of the release of pro-inflammatory cytokines as TNFα and IL1β at normal levels. Only marginal increases after microcarrier interaction were allowed. The required microcarrier optimization results in the maximum use of a carrier/cell ratio of 1:1 for biopolymer-coated carriers and a carrier/cell ratio up to 5:1 for lipid-bilayer-coated carriers during the coincubation with macrophage-like cells. Low formation of reactive oxygen species (ROS) could not be maintained by either reduced carrier/cell ratios or by a surface lipid bilayer.

Mechanism of protein release from polyelectrolyte multilayer microcapsules

The development of polyelectrolyte multilayer microcapsules as a delivery system containing bioactive compounds strongly depends on understanding of the major factors that influence capsules' loading and release of incorporated substances. Mechanism of protein release from biocompatible polyelectrolyte multilayer microcapsules has been examined using two different approaches of protein encapsulation: (i) "preloading" via coprecipitation of tetramethylrhodamine isothiocyanate (TRITC)-labeled bovine serum albumin (BSA) (TRITC-BSA) into CaCO(3) particles followed by multilayer assembly and (ii) "postloading" of TRITC-BSA in preformed empty capsules templated on pure CaCO(3) particles taken in the same amount as in "preloading" approach. Polysaccharides (alginate (Alg) or dextran sulfate (Dex)) and polyarginine (PAr) were used as layer constituents. On the basis of the effects of capsule shell composition and thickness, method of protein encapsulation, volume of the surrounding medium, and frequency of medium refreshment on protein release profile, we reveal a mechanism of protein release. The key phenomenon determining the protein release is the property of multilayer polyelectrolyte shells relating to the entrapping and accumulation of protein molecules. The results obtained together with the suggested mechanism of capsule loading and protein release allow us to propose the use of polyelectrolyte microcapsules as a depot system to supply and maintain a defined level of macromolecular drug concentration in surrounding medium.

Assembly of erodible, DNA-containing thin films on the surfaces of polymer microparticles: toward a layer-by-layer approach to the delivery of DNA to antigen-presenting cells

We report a layer-by-layer approach to the assembly of ultrathin and erodible DNA-containing films on the surfaces of polymer microparticles. DNA-containing multilayered films were fabricated layer-by-layer on the surfaces of polystyrene microspheres (approximately 6 microm) by iterative and alternating cycles of particle suspension, centrifugation and resuspension in solutions of plasmid DNA and a hydrolytically degradable polyamine. Film growth occurred in a stepwise manner, as demonstrated by characterization of the zeta potentials and fluorescence intensities of film-coated particles during film assembly. Characterization of film-coated particles by confocal fluorescence microscopy and scanning electron microscopy revealed the multilayered particle coatings to be smooth, uniform and free of large-scale physical defects. Film-coated microparticles sustained the release of transcriptionally active DNA into solution for approximately three days when incubated in physiologically relevant media. Previous studies have demonstrated that the adsorption of DNA onto the surfaces of cationic microparticles can be used to target the delivery of DNA to antigen-presenting cells. As a first step toward the application of this layer-by-layer approach to the development of methods for the delivery of DNA to antigen-presenting cells, we demonstrated that film-coated microparticles could be used to transport DNA into macrophage cells in vitro using a model mouse macrophage cell line. Our results suggest the basis of a general approach that could, with further development, prove useful for the delivery of DNA-encoded antigens to macrophages, or other antigen-presenting cells, and provide new materials-based methods for the formulation and delivery of DNA vaccines.

Fluorescent bead arrays by means of layer-by-layer polyelectrolyte adsorption

Colloids with graduated fluorescence intensities were fabricated by means of layer-wise adsorption of fluorescein isothiocyanate-labelled poly(allyl amine hydrochloride) (FITC-PAH) together with poly(styrene sulfonate) (PSS) on silica particles. The graduated fluorescence was adjusted by variation of the fluorescent layer number and mixing labelled PAH with unlabelled PAH in one layer. The graduation of fluorescence intensities was adjusted in a geometric progression. It was shown that a proper label content is crucial if self-quenching phenomena are involved. The approach of mixing FITC-PAH with unlabelled polyelectrolyte during adsorption was unsatisfactory since competition in adsorption occurs. The system shows excellent stability at least over a period of two years.

Defoliation and Plasmid Delivery with Layer-by-Layer Coated Colloids

The uptake of polyelectrolyte multilayer coated colloids into cells, subsequent defoliation and plasmid delivery was studied by means of confocal microscopy and flow cytometry. Silica particles coated layer-wise with protamine and dextran sulfate were given to HEK 293T cells. Optimum uptake was found with protamine as the top layer. The particle uptake likely follows an non-receptor-mediated endocytotic pathway. Defoliation of polyelectrolyte multilayer coated particles within cells was demonstrated by the release of incorporated plasmids as indicated by the expression of plasmid encoded proteins using the enhanced green fluorescence proteine (pEGFP-C1) plasmid and a red fluorescence protein (pDsRed1-N1) plasmid. This proves, together with the direct observation of fluorescent layer debris, the defoliation of coated particles and the release of layer components into the cytoplasm. Particle uptake and GFP expression.

Chemo-Enzymatic Synthesis of Raffinose-Branched Polyelectrolytes and Self-Assembly Application in Microcapsules

A novel biocompatible polyelectrolyte poly(vinyl raffinose-co-acrylic acid) (PRCA) containing a raffinose branch was prepared via redox polymerization using Fe(2+)/K(2)S(2)O(8)/H(2)O(2) starting from enzymatically-synthesized monomer: 1-O-vinyldecanedioyl raffinose. Copolymers with different monomer feed ratios were prepared and characterized with IR, NMR, and GPC. PRCA can be alternated with polycation to form microcapsules on a crystals template by electrostatic layer-by-layer technique. The multilayers of PRCA/poly(methacryloyloxyethyl dimethylbenzyl ammonium chloride) (PMBA) on quartz slides and PRCA/poly(dimethyldiallyl ammonium chloride) (PDDA) on acyclovir crystals template were fabricated and characterized with UV-Vis spectra, the microelectrophoretic measurement, and TEM. Hollow capsules can be formed after the removal of acyclovir crystals template in a buffer solution. The nano-capsule-carrying galactose residue is a potential targeting drug-controlled delivery systems.