We report that the aqueous self-assembly behavior of citrate based gold nanoparticles decorated with the temperature responsive RAFT-based polymer poly(N-isopropylacrylamide) critically depends on the presence of salt in the medium. Both for temperature induced reversible agglomeration and for hydrogen bonding based layer-by-layer assembly with tannic acid, the presence of salt dramatically promotes the assembly behavior. We attribute this to a combination of ionic screening of the remaining citrate groups on the nanoparticle surface and a salting out effect which increases the contribution of hydrophobic interactions in the self-assembly process. These findings provide new insights into an attractive class of polymer/gold hybrid nanomaterials that can find application in biotechnology, catalysis, and biomedicine.

No abstract

Polymeric multilayer films assembled via hydrogen-bonding are witnessing increased interest from the scientific community. Here we report on hydrogen bonded multilayers of tannic acid and neutral poly(2-oxazoline)s. Importantly we demonstrate, to the best of our knowledge, for the first time that a temperature responsive polymer, in this case poly(2-(n-propyl)-2-oxazline), can be assembled below and above its TCP with distinctly different growth mechanisms.

Poor water-solubility is becoming the leading hurdle for novel drug molecules to reach the market. Enhancing the surface-to-volume ratio by reducing the drug particles size has emerged as a powerful method to enhance the drug dissolution rate of poorly water-soluble drugs. Here we present several approaches to produce micro-and nano-suspensions of febantel and itraconazole, as poorly water-soluble model drugs, in the presence of the self-emulsifying excipient Gelucire 44/14 as additional solubility enhancing agent. Two top-down approaches involving either ball milling or ultrasound treatment, to reduce the size of existing drug crystals, were used as reference processes. Both techniques allowed to significantly reduce the size of the drug crystals and enhance the dissolution of febantel with the ultrasound treated formulation performing the best. In case of itaconazole, no influence of both processing techniques was observed, which is likely to be attributed to its extremely low water-solubility.To address this challenge, we developed a novel bottom up approach to produce nanosuspensions. This approach involved first dissolving the drug in molten Gelucire 44/14 followed by atomization into cold water. During the atomization, cavitation was induced by ultrasonication. This process yielded milky suspensions in the submicrometer range.Furthermore a fraction of the drug was found to be in amorphous state. Nanosuspensions produced by this technique showed improved dissolution behavior, both in case of febantel and itraconazole.

Here, we aim to evaluate Gelucire 44/14 as non-ionic surface-active excipient to produce immediate-release solid dosage forms for poorly water-soluble drugs. Gelucires are polyethylene glycol (PEG) glycerides composed of mono-, di- and triglycerides and mono- and diesters of PEG. They are inert semi-solid waxy amphiphilic excipients with surface-active properties that spontaneously form a fine dispersion or emulsion upon contact with water. Monolithic Gelucire 44/14 structures are prone to prolonged erosion times, thereby slowing down drug dissolution. To overcome this issue, we combine either granulation or spray-drying, followed by compression into tablets, with an optimized composition of disintegration promoting agents. This formulation strategy allows obtaining nearly 100% drug release within 10 min dissolution time.

Here we report on a simple, generally applicable method for depositing metal nanoparticles on a wide variety of solid surfaces under all aqueous conditions. Noble-metal nanoparticles obtained by citrate reduction followed by coating with thermoresponsive polymers spontaneously form a monolayer-like structure on a wide variety of substrates in presence of sodium chloride whereas this phenomenon does not occur in salt-free medium. Interestingly, this phenomenon occurs below the cloud point temperature of the polymers and we hypothesize that salt ion-induced screening of electrostatic charges on the nanoparticle surface entropically favors hydrophobic association between the polymer-coated nanoparticles and a hydrophobic substrate.

Here we report on as imple,g enerally applicable method for depositing metal nanoparticles on awide variety of solid surfaces under all aqueous conditions.N oble-metal nanoparticles obtained by citrate reduction followed by coating with thermoresponsive polymers spontaneously form amonolayer-like structure on aw ide variety of substrates in presence of sodium chloride whereas this phenomenon does not occur in salt-free medium. Interestingly,this phenomenon occurs below the cloud point temperature of the polymers and we hypothesizet hat salt ion-induced screening of electrostatic charges on the nanoparticle surface entropically favors hydrophobic association between the polymer-coated nanoparticles and ahydrophobic substrate.Nanoparticles and nanostructured films have attracted major interest for aw ide variety of applications,i ncluding for example biotechnology, [1][2][3] medicine, [4] photonics, [5][6][7][8] microelectronics, [9] and catalysis. [10] In contrast to bulk materials,f or which the physicochemical properties are sizeindependent, many nanoparticle properties strongly depend on particle size and shape. [11,12] Combining bulk materials with at hin coating of as pecific nanomaterial therefore allows to engineer the bulk material with unique high added-value properties through the coating.[13] Thec urrently available toolbox for surface modification of solid materials comprises solvent casting, [14] chemical vapor deposition [15] and aw ide variety of self-assembly approaches such as LangmuirBlodgett, [16] layer-by-layer self-assembly, [17][18][19][20] and self-assembled monolayer formation. [21,22] In recent years,n atureinspired compounds such as polyphenols and mussel-derived polydopamine that spontaneously deposit on solid substrates have fueled the interest for simple and straightforward surface coating techniques under all aqueous conditions. [23][24][25][26] Whereas these methods provide access to all-organic films, there remains an unmet need for simple assembly methods for inorganic nanoparticle coatings under aqueous conditions.Here we report on as imple,b roadly applicable method for depositing metal-nanoparticle films on aw ide variety of solid surfaces under all aqueous conditions.O ur approach is demonstrated for gold (Au NP )and silver (Ag NP )nanoparticles and allows for extremely easy engineering of bulk materials with plasmonic and catalytic functionality. Au NP were synthesized by direct reduction of HAuCl 4 in aqueous medium in presence of sodium citrate,w hich acts both as reducing and stabilizing agent. [27,28] Subsequently,the nanoparticles were coated by ligand exchange with defined trithiocarbonate end-functionalized poly(N-isopropylacrylamide) (polyNIPAm;P N-3, Table S1 in the Supporting Information; M n :4 .9 kDa, D: 1.08;F igure 1A), yielding polyNI-PA m@Au NP . [29] PolyNIPAm is at hermoresponsive polymer that undergoes an entropy driven coil-to-globule transition upon heating in aqueous solution with acloud point temperature (T cp )around 32 8 8C. Synthesis of this...