Synthesis of DNA-polypyrrole nanocapsule

Porous silver-coated pNIPAM-co-AAc hydrogel nanocapsules

This paper describes the preparation and characterization of a new type of core-shell nanoparticle in which the structure consists of a hydrogel core encapsulated within a porous silver shell. The thermo-responsive hydrogel cores were prepared by surfactant-free emulsion polymerization of a selected mixture of N-isopropylacrylamide (NIPAM) and acrylic acid (AAc). The hydrogel cores were then encased within either a porous or complete silver shell for which the localized surface plasmon resonance (LSPR) extends from visible to near-infrared (NIR) wavelengths (i.e., λ_max varies from 550 to 1050 nm, depending on the porosity), allowing for reversible contraction and swelling of the hydrogel via photothermal heating of the surrounding silver shell. Given that NIR light can pass through tissue, and the silver shell is porous, this system can serve as a platform for the smart delivery of payloads stored within the hydrogel core. The morphology and composition of the composite nanoparticles were characterized by SEM, TEM, and FTIR, respectively. UV-vis spectroscopy was used to characterize the optical properties.

Fabrication of polymer nanocapsules with controllable oligo(ethylene glycol) densities, permeation properties and robustly crosslinked walls

P(TMSPMA-co-OEGMA) nanocapsules with controllable oligo(ethylene glycol) (OEG) densities and robustly cross-linked structures were successfully fabricated from the cross-linkable copolymer, poly[3-(trimethoxysilyl)propyl methacrylate-co-oligo(ethylene glycol) methacrylate] (P(TMSPMA-co-OEGMA)). The densities of OEG segments of the resultant P(TMSPMA-co-OEGMA) nanocapsules could be easily controlled by tuning the OEGMA contents of copolymer P(TMSPMA-co-OEGMA). The microenvironments of the P(TMSPMA-co-OEGMA) nanocapsules were determined to be hydrophobic. It was demonstrated that hydrophobic pyrene could be in situ loaded into the P(TMSPMA-co-OEGMA) nanocapsules during the fabrication procedure. The release rates of pyrene from the P(TMSPMA-co-OEGMA) nanocapsules were dependent on the contents of OEGMA, indicating that the permeation properties of P(TMSPMA-co-OEGMA) nanocapsules could be tuned by varying the cross-linked densities of the nanocapsule walls. It was further demonstrated that other functional groups could be easily incorporated into the resultant polymer nanocapsules by using the similar procedure. The preparation of polymer nanocapsules with various functionalities and robustly cross-linked walls without any further post modification process, any sacrificial core and surfactant would be beneficial from scientific and technical point of views.

High-capacity conductive nanocellulose paper sheets for electrochemically controlled extraction of DNA oligomers

Highly porous polypyrrole (PPy)-nanocellulose paper sheets have been evaluated as inexpensive and disposable electrochemically controlled three-dimensional solid phase extraction materials. The composites, which had a total anion exchange capacity of about 1.1 mol kg⁻¹, were used for extraction and subsequent release of negatively charged fluorophore tagged DNA oligomers via galvanostatic oxidation and reduction of a 30–50 nm conformal PPy layer on the cellulose substrate. The ion exchange capacity, which was, at least, two orders of magnitude higher than those previously reached in electrochemically controlled extraction, originated from the high surface area (i.e. 80 m² g⁻¹) of the porous composites and the thin PPy layer which ensured excellent access to the ion exchange material. This enabled the extractions to be carried out faster and with better control of the PPy charge than with previously employed approaches. Experiments in equimolar mixtures of (dT)₆, (dT)₂₀, and (dT)₄₀ DNA oligomers showed that all oligomers could be extracted, and that the smallest oligomer was preferentially released with an efficiency of up to 40% during the reduction of the PPy layer. These results indicate that the present material is very promising for the development of inexpensive and efficient electrochemically controlled ion-exchange membranes for batch-wise extraction of biomolecules.

Spatial mapping of elemental distributions in polypyrrole-cellulose nanofibers using energy-filtered transmission electron microscopy

The energy-filtered transmission electron microscopy (EFTEM) technique has been used to study ion-exchange processes in conductive polymer composite nanofibers. The elemental distributions of carbon, nitrogen, oxygen, chlorine, boron, phosphorus, molybdenum, and sulfur within polypyrrole-cellulose nanofibers, used as potential controlled electrochemical solid phase extraction media, have been studied by EFTEM. The distribution of ions within the polypyrrole-cellulose nanofibers and the penetration depth of ions into the material as a function of the size and charge of the latter were investigated. Further, the spatial distribution of single stranded DNA hexamers inside polypyrrole-cellulose nanofibers was mapped subsequent to the electrochemically controlled extraction of DNA from a borate buffer solution. The results show that the EFTEM mapping technique provides unpreceded possibilities for studies of the distribution of ions inside conductive polymer composites.