The endocytotic mechanisms involved in the uptake of charged polystyrene nanoparticles into HeLa cells were investigated. Uptake experiments were done in the presence or absence of drugs known to inhibit various factors in endocytosis. Independent of the particle charge, endocytosis is highly dependent on dynamin, F-actin, and tyrosine-specific protein kinases, which suggests a dynamin-dependent and lipid raft-dependent mechanism. However, cholesterol depletion did not hinder particle uptake. Regarding positively charged particles, macropinocytosis, the microtubule network, and cyclooxygenases are also involved. The clathrin-dependent pathway plays a minor role.

Cross-linked potato starch nanocapsules with encapsulated dsDNA (with a defined number of base pairs, i.e., 286, 476, and 790 bp) were synthesized using the miniemulsion technique. The inverse (water-in-oil) miniemulsion system was applied to create stable aqueous nanodroplets of dissolved starch in cyclohexane as a continuous phase. The amphiphilic block copolymer poly[(ethylene-co-butylene)-b-(ethylene oxide)] was used as a surfactant to stabilize the droplets. After addition of the cross-linker, 2,4-toluene diisocyanate (TDI), the polyaddition reaction took place at the droplet's interface, resulting in the formation of a polymeric cross-linked shell. The influence of starch, surfactant, and the amount of cross-linker on the average size, size distribution, and morphology of the capsules was studied by dynamic light scattering and electron microscopy. FTIR spectroscopy was used to identify the chemical composition of the capsule shell. The permeability of the shell was studied on the fluorescent dye (i.e., sulforhodamine 101) containing capsules using fluorescence spectroscopy. High thermal stability of the cross-linked capsules allows one to perform the polymerase chain reaction inside the core. The encapsulation of dsDNA and the efficiency of the PCR were confirmed by fluorescence spectroscopy after staining with the DNA-selective dye (SYBRGreen).

No abstract

Titanium that is covered with a native oxide layer is widely used as an implant material; however, it is only passively incorporated in the human bone. To increase the implant-bone interaction, one can graft multifunctional phosphonic compounds onto the implant material. Phosphonate groups show excellent adhesion properties onto metal oxide surfaces such as titanium dioxide, and therefore, they can be used as anchor groups. Here, we present an alternative coating material composed of phosphonate surface-functionalized polystyrene nanoparticles synthesized via free radical copolymerization in a direct (oil-in-water) miniemulsion process. Two types of functional monomers, namely, vinylphosphonic acid (VPA) and vinylbenzyl phosphonic acid (VBPA), were employed in the copolymerization reaction. Using VBPA as a comonomer leads to particles with a higher density of surface phosphonate groups in comparison to those obtained with VPA. VBPA-functionalized particles were used for the coating formation on the titanium surface. The particles monolayer was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) employing titanium and silicium tip with the native OH groups. Force versus distance curves proves the strong adhesion between the phosphonated particles and the titanium (or silicium) surfaces in contrast to the nonfunctionalized polystyrene particles. Finally, as a proof of concept, the particles adhered to the surface were further used to nucleate hydroxyapatite, which has high potential for bioimplants.

No abstract

Fluorescent polyisoprene nanoparticles were synthesized by the miniemulsion technique as marker particles for cells. The uptake of the non-functionalized polyisoprene nanoparticles, without any transfection agents, into different adherent (HeLa) and also suspension (Jurkat) cell lines is strikingly efficient and fast compared to other polymeric particles, and leads to high loading of the cells. The intracellular polyisoprene particles are localized as single particles in endosomes distributed throughout the entire cytoplasm. The uptake kinetics shows that particle internalization starts during the first minutes of incubation and is finished after 48 h of incubation. Since (unfunctionalized) polystyrene particles show a comparable, low uptake behavior in cells, the uptake rates can be tuned by the amount of polystyrene in polyisoprene/polystyrene copolymer particles. As polyisoprene nanoparticles are internalized by different cell lines that are relevant for biomedical applications, they can be used to label these cells efficiently if a marker is incorporated in the particles. As polyisoprene is not or is hardly biodegradable the particles should be suited for long-term applications.

Amino-functionalized polymeric NPs are efficiently taken up by human T cells and could be used to design nanocarriers for direct access and manipulation of antigen-specific T cells in vivo.

Idiopathic pulmonary fibrosis (IPF) is a fatal disease of unknown cause that is characterized by progressive fibrotic lung remodeling. An abnormal emergence of airway epithelial‐like cells within the alveolar compartments of the lung, herein termed bronchiolization, is often observed in IPF. However, the origin of this dysfunctional distal lung epithelium remains unknown due to a lack of suitable human model systems. In this study, we established a human induced pluripotent stem cell (iPSC)‐derived air‐liquid interface (ALI) model of alveolar epithelial type II (ATII)‐like cell differentiation that allows us to investigate alveolar epithelial progenitor cell differentiation in vitro. We treated this system with an IPF‐relevant cocktail (IPF‐RC) to mimic the pro‐fibrotic cytokine milieu present in IPF lungs. Stimulation with IPF‐RC during differentiation increases secretion of IPF biomarkers and RNA sequencing (RNA‐seq) of these cultures reveals significant overlap with human IPF patient data. IPF‐RC treatment further impairs ATII differentiation by driving a shift toward an airway epithelial‐like expression signature, providing evidence that a pro‐fibrotic cytokine environment can influence the proximo‐distal differentiation pattern of human lung epithelial cells. In conclusion, we show for the first time, the establishment of a human model system that recapitulates aspects of IPF‐associated bronchiolization of the lung epithelium in vitro.