Browsing by Subject "CLICK CHEMISTRY"

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  • Nahm, Daniel; Weigl, Franziska; Schaefer, Natascha; Sancho, Ana; Frank, Andreas; Groll, Jürgen; Villmann, Carmen; Schmidt, Hans-Werner; Dalton, Paul D.; Luxenhofer, Robert (2020)
    In this study, we designed a novel biomaterial ink platform based on hydrophilic poly(2-ethyl-2-oxazine) (PEtOzi) specifically for melt electrowriting (MEW). This material crosslinks spontaneously after processing via dynamic Diels–Alder click chemistry. These direct-written microperiodic structures rapidly swell in water to yield thermoreversible hydrogels. These hydrogels are robust enough for repeated aspiration and ejection through a cannula without structural damage, despite their high water content of 84%. Moreover, the scaffolds retain functional groups for modification using click chemistry and therefore can be readily functionalized as demonstrated using fluorophores and peptides to facilitate visualization and cell attachment. The PEtOzi hydrogel developed here is compatible with confocal imaging and staining protocols for cells. In summary, an advanced material platform based on PEtOzi is reported that is compatible with MEW and results in functionalizable chemically crosslinked microperiodic hydrogels.
  • Gulumkar, Vijay; Äärelä, Antti; Moisio, Olli; Rahkila, Jani; Tähtinen, Ville; Leimu, Laura; Korsoff, Niko; Korhonen, Heidi; Poijärvi-Virta, Päivi; Mikkola, Satu; Nesati, Victor; Vuorimaa-Laukkanen, Elina; Viitala, Tapani; Yliperttula, Marjo; Roivainen, Anne; Virta, Pasi (2021)
    An azide-functionalized 12-armed Buckminster fullerene has been monosubstituted in organic media with a substoichiometric amount of cyclooctyne-modified oligonucleo-tides. Exposing the intermediate products then to the same reaction (i. e., strain-promoted alkyne-azide cycloaddition, SPAAC) with an excess of slightly different oligonucleotide constituents in an aqueous medium yields molecularly defined monofunctionalized spherical nucleic acids (SNAs). This procedure offers a controlled synthesis scheme in which one oligonucleotide arm can be functionalized with labels or other conjugate groups (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, DOTA, and Alexa-488 demonstrated), whereas the rest of the 11 arms can be left unmodified or modified by other conjugate groups in order to decorate the SNAs' outer sphere. Extra attention has been paid to the homogeneity and authenticity of the C60-azide scaffold used for the assembly of full-armed SNAs.
  • Selin, Markus; Nummelin, Sami; Deleu, Jill; Ropponen, Jarmo; Viitala, Tapani; Lahtinen, Manu; Koivisto, Jari; Hirvonen, Jouni; Peltonen, Leena; Kostiainen, Mauri A.; Bimbo, Luis M. (2018)
    Pharmaceutical nanosuspensions are formed when drug crystals are suspended in aqueous media in the presence of stabilizers. This technology offers a convenient way to enhance the dissolution of poorly water-soluble drug compounds. The stabilizers exert their action through electrostatic or steric interactions, however, the molecular requirements of stabilizing agents have not been studied extensively. Here, four structurally related amphiphilic Janus-dendrimers were synthesized and screened to determine the roles of different macromolecular domains on the stabilization of drug crystals. Physical interaction and nanomilling experiments have substantiated that Janus-dendrimers with fourth generation hydro- philic dendrons were superior to third generation analogues and Poloxamer 188 in stabilizing indomethacin suspensions. Contact angle and surface plasmon resonance measurements support the hypothesis that Janus-dendrimers bind to indomethacin surfaces via hydrophobic interactions and that the number of hydrophobic alkyl tails determines the adsorption kinetics of the Janus-dendrimers. The results showed that amphiphilic Janus-dendrimers adsorb onto drug particles and thus can be used to provide steric stabilization against aggregation and recrystallization. The modular synthetic route for new amphiphilic Janus-dendrimers offers, thus, for the first time a versatile platform for stable general-use stabilizing agents of drug suspensions.
  • Lumen, Dave; Näkki, Simo; Imlimthan, Surachet; Lambidis, Elisavet; Sarparanta, Mirkka; Xu, Wujun; Lehto, Vesa-Pekka; Airaksinen, Anu J. (2019)
    Polyethylene glycol (PEG) has been successfully used for improving circulation time of several nanomaterials but prolonging the circulation of porous silicon nanoparticles (PSi NPs) has remained challenging. Here, we report a site specific radiolabeling of dual-PEGylated thermally oxidized porous silicon (DPEG-TOPSi) NPs and investigation of influence of the PEGylation on blood circulation time of TOPSi NPs. Trans-cyclooctene conjugated DPEG-TOPSi NPs were radiolabeled through a click reaction with [In-111]In-DOTA-PEG(4)-tetrazine (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) and the particle behavior was evaluated in vivo in Balb/c mice bearing 4T1 murine breast cancer allografts. The dual-PEGylation significantly prolonged circulation of [In-111]In-DPEG-TOPSi particles when compared to non-PEGylated control particles, yielding 10.8 +/- 1.7% of the injected activity/g in blood at 15 min for [In-111]In-DPEG-TOPSi NPs. The improved circulation time will be beneficial for the accumulation of targeted DPEG-TOPSi to tumors.