Anisotropic Particle Deposition Kinetics from Quartz Crystal Microbalance Measurements: Beyond the Sphere Paradigm

Deposition kinetics of polymer particles characterized by a prolate spheroid shape on gold sensors modified by the adsorption of poly(allylamine) was investigated using a quartz crystal microbalance and atomic force microscopy. Reference measurements were also performed for polymer particles of a spherical shape and the same diameter as the spheroid shorter axis. Primarily, the frequency and dissipation shifts for various overtones were measured as a function of time. These kinetic data were transformed into the dependence of the complex impedance, scaled up by the inertia impedance, upon the particle size to the hydrodynamic boundary layer ratio. The results obtained for low particle coverage were interpolated, which enabled the derivation of Sauerbrey-like equations, yielding the real particle coverage using the experimental frequency or dissipation (bandwidth) shifts. Experiments carried out for a long deposition time confirmed that, for spheroids, the imaginary and real impedance components were equal to each other for all overtones and for a large range of particle coverage. This result was explained in terms of a hydrodynamic, lubrication-like contact of particles with the sensor, enabling their sliding motion. In contrast, the experimental data obtained for spheres, where the impedance ratio was a complicated function of overtones and particle coverage, showed that the contact was rather stiff, preventing their motion over the sensor. It was concluded that results obtained in this work can be exploited as useful reference systems for a quantitative interpretation of bioparticle, especially bacteria, deposition kinetics on macroion-modified surfaces.

Influence of hydrophilic block length on the aggregation properties of polyglycidol-polystyrene-polyglycidol copolymers

Amphiphilic triblock copolymers, polyglycidol-polystyrene-polyglycidol (PGL-PS-PGL), were synthesised via anionic polymerization starting from the synthesis of a polystyrene macroinitiator with 60 styrene units in the block terminated by ethylene oxide. Poly(ethoxyethyl glycidyl ether) blocks of different lengths were created on both sides of the macroinitiator. By removing the ethoxyethyl blocking groups, PGL-PS-PGL copolymers containing polyglycidol blocks with DP 11, 23, 44 and 63 were received. Their structures were determined by NMR and FTIR. The hydrophilicity of PLG-PS-PGL films was studied upon exposure to water vapour. To perform the copolymers' aggregation in water, the samples were dialysed from DMF into water. The critical concentration of their micellisation (CMC) was determined by measuring the absorbance of the 1,6-diphenylhexa-1,3,5-triene (DPH) probe and the intensity of light scattered by the copolymers' solution as a function of concentration. CMC values increased with increasing the number of hydrophilic glycidol units in the copolymer chain. The sizes of aggregates formed slightly above the critical concentration were measured by dynamic light scattering (DLS), and particles were imaged by cryo-TEM. Cryo-TEM pictures showed the presence of regular micelles in copolymer dispersions. For copolymers with shorter PGL chains aggregated partices were detected. Moreover, cryo-TEM demonstrated that the copolymers with a polyglycidol block of DP = 63 formed regular spherical micelles that formed 2D ordered organisation on the surface. X-ray measurements showed the formation of a partially crystallised PS core in the micelle's interior. The aggregates of all copolymers were stable. Their sizes did not change after one year of storage. The particles did not disassociate even after diluting their dispersions to a concentration 10 times lower than the critical concentration.

Lipopolysaccharide Primes Human Macrophages for Noncanonical Inflammasome-Induced Extracellular Vesicle Secretion

Human macrophages secrete extracellular vesicles (EVs) loaded with numerous immunoregulatory proteins. Vesicle-mediated protein secretion in macrophages is regulated by poorly characterized mechanisms; however, it is now known that inflammatory conditions significantly alter both the quantities and protein composition of secreted vesicles. In this study, we employed high-throughput quantitative proteomics to characterize the modulation of EV-mediated protein secretion during noncanonical caspase-4/5 inflammasome activation via LPS transfection. We show that human macrophages activate robust caspase-4-dependent EV secretion upon transfection of LPS, and this process is also partially dependent on NLRP3 and caspase-5. A similar effect occurs with delivery of the LPS with Escherichia coli-derived outer membrane vesicles. Moreover, sensitization of the macrophages through TLR4 by LPS priming prior to LPS transfection dramatically augments the EV-mediated protein secretion. Our data demonstrate that this process differs significantly from canonical inflammasome activator ATP-induced vesiculation, and it is dependent on the autocrine IFN signal associated with TLR4 activation. LPS priming preceding the noncanonical inflammasome activation significantly enhances vesicle-mediated secretion of inflammasome components caspase-1, ASC, and lytic cell death effectors GSDMD, MLKL, and NINJ1, suggesting that inflammatory EV transfer may exert paracrine effects in recipient cells. Moreover, using bioinformatics methods, we identify 15-deoxy-Δ12,14-PGJ2 and parthenolide as inhibitors of caspase-4-mediated inflammation and vesicle secretion, indicating new therapeutic potential of these anti-inflammatory drugs.

QCM-D Investigations of Anisotropic Particle Deposition Kinetics: Evidences of the Hydrodynamic Slip Mechanisms

Deposition kinetics of positively charged polymer microparticles, characterized by prolate spheroid shape, at silica and gold sensors was investigated using the quartz microbalance (QCM) technique. Reference measurements were also performed for positively charged polymer particles of spherical shape and the same mass as the spheroids. Primarily, the frequency and bandwidth shifts for various overtones were measured as a function of time. It is shown that the ratio of these signals is close to unity for all overtones. These results were converted to the dependence of the frequency shift on the particle coverage, directly determined by atomic force microscopy and theoretically interpreted in terms of the hydrodynamic model. A quantitative agreement with experiments was attained considering particle slip relative to the ambient oscillating flow. In contrast, the theoretical results pertinent to the rigid contact model proved inadequate. The particle deposition kinetics derived from the QCM method was compared with theoretical modeling performed according to the random sequential adsorption approach. This allowed to assess the feasibility of the QCM technique to furnish proper deposition kinetics for anisotropic particles. It is argued that the hydrodynamic slip effect should be considered in the interpretation of QCM kinetic results acquired for bioparticles, especially viruses.

Synthesis, Hydrophilicity and Micellization of Coil-Brush Polystyrene-b-(polyglycidol-g-polyglycidol) Copolymer-Comparison with Linear Polystyrene-b-polyglycidol

In this paper, an original method of synthesis of Coil-Brush amphiphilic polystyrene-b-(polyglycidol-g-polyglycidol) (PS-b-(PGL-g-PGL)) block copolymers was developed. The hypothesis that their hydrophilicity and micellization can be controlled by polyglycidol blocks architecture was verified. The research enabled comparison of behavior in water of PS-b-PGL copolymers and block-brush copolymers PS-b-(PGL-g-PGL) with similar composition. The Coil-Brush copolymers were composed of PS-b-PGL linear core with average DPn of polystyrene 29 and 13 of polyglycidol blocks. The DPn of polyglycidol side blocks of coil-b-brush copolymers were 2, 7, and 11, respectively. The copolymers were characterized by 1H and 13C NMR, GPC, and FTIR methods. The hydrophilicity of films from the linear and Coil-Brush copolymers was determined by water contact angle measurements in static conditions. The behavior of Coil-Brush copolymers in water and their critical micellization concentration (CMC) were determined by UV-VIS using 1,6-diphenylhexa-1,3,5-trien (DPH) as marker and by DLS. The CMC values for brush copolymers were much higher than for linear species with similar PGL content. The results of the copolymer film wettability and the copolymer self-assembly studies were related to fraction of hydrophilic polyglycidol. The CMC for both types of polymers increased exponentially with increasing content of polyglycidol.

Anti-Inflammatory Effect of Very High Dose Local Vessel Wall Statin Administration: Poly(L,L-Lactide) Biodegradable Microspheres with Simvastatin for Drug Delivery System (DDS)

Atherosclerosis involves an ongoing inflammatory response of the vascular endothelium and vessel wall of the aorta and vein. The pleiotropic effects of statins have been well described in many in vitro and in vivo studies, but these effects are difficult to achieve in clinical practice due to the low bioavailability of statins and their first-pass metabolism in the liver. The aim of this study was to test a vessel wall local drug delivery system (DDS) using PLA microstructures loaded with simvastatin. Wistar rats were fed high cholesterol chow as a model. The rat vessels were chemically injured by repeated injections of perivascular paclitaxel and 5-fluorouracil. The vessels were then cultured and treated by the injection of several concentrations of poly(L,L-lactide) microparticles loaded with the high local HMG-CoA inhibitor simvastatin (0.58 mg/kg) concentration (SVPLA). Histopathological examinations of the harvested vessels and vital organs after 24 h, 7 days and 4 weeks were performed. Microcirculation in mice as an additional test was performed to demonstrate the safety of this approach. A single dose of SVPLA microspheres with an average diameter of 6.4 μm and a drug concentration equal to 8.1% of particles limited the inflammatory reaction of the endothelium and vessel wall and had no influence on microcirculation in vivo or in vitro. A potent pleiotropic (anti-inflammatory) effect of simvastatin after local SVPLA administration was observed. Moreover, significant concentrations of free simvastatin were observed in the vessel wall (compared to the maximum serum level). In addition, it appeared that simvastatin, once locally administered as SVPLA particles, exerted potent pleiotropic effects on chemically injured vessels and presented anti-inflammatory action. Presumably, this effect was due to the high local concentrations of simvastatin. No local or systemic side effects were observed. This approach could be useful for local simvastatin DDSs when high, local drug concentrations are difficult to obtain, or systemic side effects are present.

Functionalized Particles Designed for Targeted Delivery

Pure bioactive compounds alone can only be exceptionally administered in medical treatment. Usually, drugs are produced as various forms of active compounds and auxiliary substances, combinations assuring the desired healing functions. One of the important drug forms is represented by a combination of active substances and particle-shaped polymer in the nano- or micrometer size range. The review describes recent progress in this field balanced with basic information. After a brief introduction, the paper presents a concise overview of polymers used as components of nano- and microparticle drug carriers. Thereafter, progress in direct synthesis of polymer particles with functional groups is discussed. A section is devoted to formation of particles by self-assembly of homo- and copolymer-bearing functional groups. Special attention is focused on modification of the primary functional groups introduced during particle preparation, including introduction of ligands promoting anchorage of particles onto the chosen living cell types by interactions with specific receptors present in cell membranes. Particular attention is focused on progress in methods suitable for preparation of particles loaded with bioactive substances. The review ends with a brief discussion of the still not answered questions and unsolved problems.

Synthesis of Bioerodible Poly(ε-caprolactone) Latexes and Poly(D, L-lactide) Microspheres by Ring-Opening Polymerization

Poly(ε-caprolactone) [poly(CL)] latexes and poly(D,L-lactide) [poly(D,L-Lc)] microspheres were prepared directly by ring-opening precipita tion polymerization carried out in heptane-dioxane (4:1 v/v) mixed solvent in the presence of poly(dodecyl acrylate)-g-poly(ε-caprolactone) used as the surface active agent. This designed synthetic method yielded latexes and microspheres with narrow size distribution; poly(CL) latex Dv/Dn = 1.038 and for poly(D,L- Lc) microspheres Dv/Dn = 1.15. (Dv and Dn denote the volume and number average diameters of particles.) The poly(CL) latex, synthesized by using CH3CH2OAl(CH2CH3) 2 as initiator, had a narrow polymer polydispersity of 1.11. Poly(D,L-Lc) microspheres, besides polymer with Mw/M n = 1.05 contained some unreacted lactide. Adsorption of human serum albumin and human gamma globulins on both kinds of polyester particles was studied for their potential use as polypeptide and protein delivery systems.

Polyglycidol, Its Derivatives, and Polyglycidol-Containing Copolymers-Synthesis and Medical Applications

Polyglycidol (or polyglycerol) is a biocompatible polymer with a main chain structure similar to that of poly(ethylene oxide) but with a ⁻CH₂OH reactive side group in every structural unit. The hydroxyl groups in polyglycidol not only increase the hydrophilicity of this polymer but also allow for its modification, leading to polymers with carboxyl, amine, and vinyl groups, as well as to polymers with bonded aliphatic chains, sugar moieties, and covalently immobilized bioactive compounds in particular proteins. The paper describes the current state of knowledge on the synthesis of polyglycidols with various topology (linear, branched, and star-like) and with various molar masses. We provide information on polyglycidol-rich surfaces with protein-repelling properties. We also describe methods for the synthesis of polyglycidol-containing copolymers and the preparation of nano- and microparticles that could be derived from these copolymers. The paper summarizes recent advances in the application of polyglycidol and polyglycidol-containing polymers as drug carriers, reagents for diagnostic systems, and elements of biosensors.

Nanoparticles from polylactide and polyether block copolymers: formation, properties, encapsulation, and release of pyrene--fluorescent model of hydrophobic drug

Polylactide-b-polyglycidol-b-poly(ethylene oxide) terpolymers and their derivatives with carboxyl and 4-(phenylazo)phenyl labels in polyglycidol blocks were used for formation of nanoparticles. Nanoparticles were produced by self assembly of terpolymer macromolecules in water above the critical aggregation concentration and by dialysis of terpolymer solutions in 1,4-dioxane against water. For terpolymers with 4-(phenylazo)phenyl labels critical aggregation concentrations increased after irradiation with UV light (300 < lambda < 400 nm) inducing conformational change of the label from trans- to cis-conformation. Diameters of nanoparticles obtained by self-assembly of macromolecules ranged from 20 to 44 nm. Dialysis yielded nanoparticles with bimodal diameter distribution. One fraction had diameters below 35 nm and diameters of the second fraction were in a range from 350 to 2300 nm, depending on terpolymer structure. Mixtures of terpolymers with poly(L,L-lactide) and poly(D,D-lactide) blocks yielded nanoparticles with diameters from 350 to 440 nm. Pyrene was incorporated into nanoparticles by partition between solution and nanoparticles or directly during particle formation by dialysis. Monitoring of pyrene release from nanoparticles suggests that a fraction of this compound was entrapped into the polylactide core whereas the remaining one was located in the polyether rich shell. The release from shells is faster for nanoparticles made from copolymers with carboxyl labels in polyglycidol blocks.

Poly(L,L-lactide) and poly(L,L-lactide-co-glycolide) microparticles by dialysis

Formation of poly(L,L-lactide) (PLLA) and poly(D,L-lactide-co-glycolide) (PLGA) microparticles by dialysis from 1,4-dioxane, tetrahydrofuran (THF), acetonitrile, dimethyl sulfoxide (DMSO), and dimethylformamide (DMF) against water has been investigated. In some instances microparticles were obtained from a mixture of the above-mentioned polyesters and PLLA-block-polyglycidol-blockpoly( ethylene oxide) triblock copolymer containing a hydrophobic PLLA block as well as hydrophilic polyglycidol and poly(ethylene oxide) blocks, the former with functional -OH groups. The effects of the nature of polyester, solvent and concentration of triblock copolymer on particles morphology, size, size distribution, and degree of crystallinity have been determined. Dialysis of PLGA yielded particles in the form of microspheres regardless of the solvent. Diameters of these particles were in the range of 0.36 - 1.77 μm and particles’ diameter polydispersity (Dw̅/Dn̅ ) varied from 1.37 to 2.04, depending on the solvent. In the case of PLLA, microspheres were obtained only by dialysis from 1,4-dioxane solutions. Dialysis of PLLA solutions in THF, acetonitrile and DMF yielded particles in the form of microcrystals. In the case of dialysis of PLLA solutions in DMSO, the product was in form of crystalline flakes of c. 1 μm thickness. Microspheres composed of PLGA were amorphous. The degree of crystallinity of microparticles from PLLA was in the range of 39% - 72%.

Phase transfer and characterization of poly(epsilon-caprolactone) and poly(L-lactide) microspheres

A method suitable for transfer of poly(epsilon-caprolactone) and poly(L-lactide) microspheres (synthesized by pseudoanionic dispersion polymerization of epsilon-caprolactone and L-lactide in heptane-1,4-dioxane mixed solvent) from heptane to water was developed. This method consists of treating the microspheres with KOH-ethanol in the presence of surfactants (nonionic Triton X-405, anionic sodium dodecyl sulfate (SDS), and zwitterionic ammonium sulfobetaine-2 (ASB)). Partial hydrolysis of polyesters results in the formation of hydroxyl and carboxyl groups in the surface layer of microspheres and enhances their stability in water-based media. Minimal concentrations of surfactants, needed to obtain stable suspensions of particles, were equal to 3 x 10(-2) and 6 x 10(-2), and 3 x 10(-2) mol l(-1) for Triton X-405. SDS, and ASB, respectively. In the case of poly(epsilon-caprolactone) microspheres, suspensions in water were stable for all three surfactants for pH values ranging from 3 to 11. Suspensions of poly(L-lactide) were stable in the same range of pH values only for ASB. Surface charge density determined by electrophoretic mobility varied for poly(epsilon-caprolactone) microspheres from 2.6 x 10(-7) to 8.9 x 10(-7) mol m(-2), for particles stabilized with Triton X-405 and ASB. respectively. In the case of poly(L-lactide) microspheres, surface charge density varied from 3.9 x 10(-7) (stabilizer: Triton X-405) to 7.4 x 10(-7) mol m(-2) (stabilizer: ASB). Carboxyl groups located in the surface layer of poly(L-lactide) microspheres were used for covalent immobilization of 6-aminoquinoline, a fluorophore with an amino group. Maximum surface concentration of immobilized 6-aminoquinoline was equal to 1.9 x 10(-6) mol m(-2). Poly(epsilon-caprolactone) microspheres transferred into water were loaded with ethyl salicylate. Loading up to 38% (w/w) was obtained.