Encapsulation of Nanoparticles with Statistical Copolymers with Different Surface Charges and Analysis of Their Interactions with Proteins and Cells.

Encapsulation with polymers is a well-known strategy to stabilize and functionalize nanomaterials and tune their physicochemical properties. Amphiphilic copolymers are promising in this context, but their structural diversity and complexity also make understanding and predicting their behavior challenging. This is particularly the case in complex media which are relevant for intended applications in medicine and nanobiotechnology. Here, we studied the encapsulation of gold nanoparticles and quantum dots with amphiphilic copolymers differing in their charge and molecular structure. Protein adsorption to the nanoconjugates was studied with fluorescence correlation spectroscopy, and their surface activity was studied with dynamic interfacial tensiometry. Encapsulation of the nanoparticles without affecting their characteristic properties was possible with all tested polymers and provided good stabilization. However, the interaction with proteins and cells significantly depended on structural details. We identified statistical copolymers providing strongly reduced protein adsorption and low unspecific cellular uptake. Interestingly, different zwitterionic amphiphilic copolymers showed substantial differences in their resulting bio-repulsive properties. Among the polymers tested herein, statistical copolymers with sulfobetaine and phosphatidylcholine sidechains performed better than copolymers with carboxylic acid- and dimethylamino-terminated sidechains.

Joining Two Natural Motifs: Catechol-Containing Poly(phosphoester)s.

Numerous catechol-containing polymers, including biodegradable polymers, are currently heavily discussed for modern biomaterials. However, there is no report combining poly(phosphoester)s (PPEs) with catechols. Adhesive PPEs have been prepared via acyclic diene metathesis polymerization. A novel acetal-protected catechol phosphate monomer was homo- and copolymerized with phosphoester comonomers with molecular weights up to 42000 g/mol. Quantitative release of the catechols was achieved by careful hydrolysis of the acetal groups without backbone degradation. Degradation of the PPEs under basic conditions revealed complete and statistical degradation of the phosphotri- to phosphodiesters. In addition, a phosphodiester monomer with an adhesive P-OH group and no protective group chemistry was used to compare the binding to metal oxides with the multicatechol-PPEs. All PPEs can stabilize magnetite particles (NPs) in polar solvents, for example, methanol, due to the binding of the phosphoester groups in the backbone to the particles. ITC measurements reveal that multicatechol PPEs exhibit a higher binding affinity to magnetite NPs compared to PPEs bearing phosphodi- or phosphotriesters as repeating units. In addition, the catechol-containing PPEs were used to generate organo- and hydrogels by oxidative cross-linking, due to cohesive properties of catechol groups. This unique combination of two natural adhesive motives, catechols and phosphates, will allow the design of novel future gels for tissue engineering applications or novel degradable adhesives.

Triblock Terpolymers by Simultaneous Tandem Block Polymerization (STBP).

A route of synthesizing triblock terpolymers in a one-pot, "one-step" polymerization approach is presented. The combination of two distinct polymerization techniques through orthogonal catalyst/initiator functionalities attached to a polymeric linker furnishes novel pathways to ABC-terpolymers. Both polymerizations have to be compatible regarding mechanisms, chosen monomers, and solvents. Here, an α,ω-heterobifunctional poly(ethylene glycol) serves as poly-meric catalyst/initiator to obtain triblock terpolymers of poly(norbornene)-b-poly(ethylene glycol)-b-poly(L-lactic acid) PNB-PEG-PLLA via simultaneous ring opening metathesis poly-merization and ring opening polymerization in a fast one-pot polymerization. Structural characterization of the polymers is provided via (1)H-, DOSY-, and (1)H,(1)H-COSY-NMR, while solution and thin film self-assembly are investigated by dynamic light scattering and atomic force microscopy.

Poly(isobutylene) nanoparticles via cationic polymerization in nonaqueous emulsions.

The preparation of poly(isobutylene) (PIB) nanoparticles via cationic emulsion polymerization is presented. As a requirement, an oil-in-perfluoroalkane nonaqueous emulsion is developed, which is inert under the carbocationic polymerization conditions. To stabilize the dichloromethane/hexane droplets in the fluorinated, continuous phase, an amphiphilic block copolymer emulsifier is prepared containing PIB and 1H,1H-perfluoroalkylated poly(pentafluorostyrene) blocks. This system allows for the polymerization of isobutylene with number-average molecular weights (Mn) up to 27,000 g mol(-1). The particle morphologies are characterized via dynamic light scattering and electron microscopy. For Mn > 20,000 g mol(-1), the particles exhibit shape-persistence at room temperature and are ≈100 nm in diameter.

Tuning polarity of polyphenylene dendrimers by patched surface amphiphilicity--precise control over size, shape, and polarity.

In the ideal case, a precise synthesis yields molecules with a constitutional as well as a conformational perfectness. Such a case of precision is demonstrated by the synthesis of semi-rigid amphiphilic polyphenylene dendrimers (PPDs). Polar sulfonate groups are precisely placed on their periphery in such a manner that patches of polar and non-polar regions are created. Key structural features are the semi-rigid framework and shape-persistent nature of PPDs since the limited flexibility introduces a nano-phase-separated amphiphilic rim of the dendrimer. This results in both attractive and repulsive interactions with a given solvent. Frustrated solvent structures then lead to a remarkable solubility in solvents of different polarity such as toluene, methanol, and water or their mixtures. Water solubility combined with defined surface structuring and variable hydrophobicity of PPDs that resemble the delicate surface textures of proteins are important prerequisites for their biological and medical applications based upon cellular internalization.

Biocompatible polylactide-block-polypeptide-block-polylactide nanocarrier.

Polypeptides are successfully incorporated into poly(l-lactide) (PLLA) chains in a ring-opening polymerization (ROP) of l-lactide by using them as initiators. The resulting ABA triblock copolymers possess molecular weights up to 11000 g·mol(-1) and polydispersities as low as 1.13, indicating the living character of the polymerization process. In a nonaqueous emulsion, peptide-initiated polymerization of l-lactide leads to well-defined nanoparticles, consisting of PLLA-block-peptide-block-PLLA copolymer. These nanoparticles are easily loaded by dye-encapsulation and transferred into aqueous media without aggregation (average diameter of 100 nm) or significant dye leakage. Finally, internalization of PLLA-block-peptide-block-PLLA nanoparticles by HeLa cells is demonstrated by a combination of coherent anti-Stokes Raman spectroscopy (CARS) and fluorescence microscopy. This demonstrates the promise of their utilization as cargo delivery vehicles.

Novel fluorescent core-shell nanocontainers for cell membrane transport.

The synthesis and characterization of novel core-shell macromolecules consisting of a fluorescent perylene-3,4,9,10-tetracarboxdiimide chromophore in the center surrounded by a hydrophobic polyphenylene shell as a first and a flexible hydrophilic polymer shell as a second layer was presented. Following this strategy, several macromolecules bearing varying polymer chain lengths, different polymer shell densities, and increasing numbers of positive and negative charges were achieved. Because all of these macromolecules reveal a good water solubility, their ability to cross cellular membranes was investigated. In this way, a qualitative relationship between the molecular architecture of these macromolecules and the biological response was established.

An autonomic self-healing organogel with a photo-mediated modulus.

A new method is described for fabricating autonomic, self-healing, deformable organogels. We combined imidazolium-based poly(ionic liquid) (PIL) and azobenzene-grafted poly(carboxylic acid) (PAA-Azo) in N,N-dimethyl formamide. Further, complexing PIL with unirradiated (trans) or irradiated (cis) PAA-Azo tuned the elastic modulus of the organogel.

Polycarbonate and polystyrene nanoplastic particles act as stressors to the innate immune system of fathead minnow (Pimephales promelas).

Water pollution with large-scale and small-scale plastic litter is an area of growing concern. Macro-plastic litter is a well-known threat to aquatic wildlife; however, the effects of micro-sized and nano-sized plastic particles on the health of organisms are not well understood. Small-scale plastic particles can easily be ingested by various aquatic organisms and potentially interfere with their immune system; therefore, the authors used a freshwater fish species as a model organism for nanoplastic exposure. Characterization of polystyrene (41.0 nm) and polycarbonate (158.7 nm) nanoplastic particles (PSNPs and PCNPs, respectively) in plasma was performed, and the effects of PSNPs and PCNPs on the innate immune system of fathead minnow were investigated. In vitro effects of PSNPs and PCNPs on neutrophil function were determined using a battery of neutrophil function assays. Exposure of neutrophils to PSNPs or PCNPs caused significant increases in degranulation of primary granules and neutrophil extracellular trap release compared to a nontreated control, whereas oxidative burst was less affected. The present study outlines the stress response of the cellular component of fish innate immune system to polystyrene and polycarbonate nanoparticles/aggregates and indicates their potential to interfere with disease resistance in fish populations. Environ Toxicol Chem 2016;35:3093-3100. © 2016 SETAC.

Evaluation of quantum dot cytotoxicity: interpretation of nanoparticle concentrations versus intracellular nanoparticle numbers.

While substantial progress has been achieved in the design of more biocompatible nanoparticles (NP), detailed data are required on the precise interactions of NPs and their environment for more reliable interpretation of toxicity results. Therefore, this study aims to investigate the interaction of two quantum dots (QDs) of the same core material CdSe/ZnS coated with two different amphiphilic polymers, with two well-established mammalian cell lines representing possible sites of QD accumulation. Results are linked to either extracellular QD concentrations (given dose) or cellular QD levels (number of internalized particles). In this study, QD internalization, effects on cellular homeostasis, and consequent inflammatory and cytoskeletal alterations caused by these QDs were explored. Fluorescence imaging techniques, including; image-based flow cytometry, confocal microscopy and high-content imaging with the InCell analyzer were used in a multiparametric methodology to evaluate cell viability, induction of oxidative stress, mitochondrial health, cell cytoskeletal functionality and changes in cellular morphology. Gene expression arrays were also carried out on 168 key genes involved in the cytoskeletal architecture and inflammatory pathway accompanied with the analysis of focal adhesions as key markers for actin-mediated signaling. Our results show distinct differences between the PMA and PTMAEMA-stat-PLMA coated QDs, which could mainly be attributed to differences in their cellular uptake levels. The toxicity profiles of both QD types changed drastically depending on whether effects were expressed in terms of given dose or internalized particles. Both QDs triggered alterations to important but different genes, most remarkably the up-regulation of tumor suppression and necrosis genes and the down regulation of angiogenesis and metastasis genes at sub-cytotoxic concentrations of these QDs.

Polymer-coated nanoparticles interacting with proteins and cells: focusing on the sign of the net charge.

To study charge-dependent interactions of nanoparticles (NPs) with biological media and NP uptake by cells, colloidal gold nanoparticles were modified with amphiphilic polymers to obtain NPs with identical physical properties except for the sign of the charge (negative/positive). This strategy enabled us to solely assess the influence of charge on the interactions of the NPs with proteins and cells, without interference by other effects such as different size and colloidal stability. Our study shows that the number of adsorbed human serum albumin molecules per NP was not influenced by their surface charge. Positively charged NPs were incorporated by cells to a larger extent than negatively charged ones, both in serum-free and serum-containing media. Consequently, with and without protein corona (i.e., in serum-free medium) present, NP internalization depends on the sign of charge. The uptake rate of NPs by cells was higher for positively than for negatively charged NPs. Furthermore, cytotoxicity assays revealed a higher cytotoxicity for positively charged NPs, associated with their enhanced uptake.

A universal scheme to convert aromatic molecular monolayers into functional carbon nanomembranes.

Free-standing nanomembranes with molecular or atomic thickness are currently explored for separation technologies, electronics, and sensing. Their engineering with well-defined structural and functional properties is a challenge for materials research. Here we present a broadly applicable scheme to create mechanically stable carbon nanomembranes (CNMs) with a thickness of ~0.5 to ~3 nm. Monolayers of polyaromatic molecules (oligophenyls, hexaphenylbenzene, and polycyclic aromatic hydrocarbons) were assembled and exposed to electrons that cross-link them into CNMs; subsequent pyrolysis converts the CNMs into graphene sheets. In this transformation the thickness, porosity, and surface functionality of the nanomembranes are determined by the monolayers, and structural and functional features are passed on from the molecules through their monolayers to the CNMs and finally on to the graphene. Our procedure is scalable to large areas and allows the engineering of ultrathin nanomembranes by controlling the composition and structure of precursor molecules and their monolayers.

Nanostructured coatings by adhesion of phosphonated polystyrene particles onto titanium surface for implant material applications.

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.

Losing the expression of molecular chirality in self-assembled physisorbed monolayers.

STM imaging on graphite of the S-enantiomer of a chiral diacetylene isophthalic acid derivative reveals that molecular chirality is not expressed in the monolayer due to a specific molecular conformation preventing the stereogenic center to transfer its chiral information.