Preparation of soft hydrogel nanoparticles with PNIPAm hair and characterization of their temperature-induced aggregation.
ABSTRACT There exists a great number of publications concerning the synthesis of core-shell and/or hairy particles by means of controlled/living polymerization. Nevertheless, how to fabricate ultrafine nanosized hairy particles, especially polymeric soft hairy particles, remains a significant challenge. This paper presents a simple self-developed approach consisting of a two-step photoinduced polymerization of cross-linked polyacrylamide (CLPAM) soft hydrogel nanoparticles (5-10 nm in diameter) grafted with poly(N-isopropylacrylamide) (PNIPAm) chains. The architecture of such ultrafine soft water-swollen CLPAM@PNIPAm core/shell nanoparticles (20-35 nm in diameter) demonstrated very specific temperature sensitive behaviors. During heating a fast association process was observed at approximately 33-34 degrees C and the singular hairy particles with 34 nm diameters clustered into aggregates that were approximately 120 nm in diameter. Raising the temperature further, however, led to a decrease in size to about 100 nm at 45 degrees C. This behavior was attributed to the formation of hydrophobic shell layers accompanying the shrinkage of PNIPAm chains with chain polar transformations. With the contraction pressure produced by further shrinkage of the hydrophobic shell layers, the soft fully swollen PAM cores expelled water and diminished in size. During the cooling process, these contracted cores that were trapped in the aggregates gave rise to an early dissociation. The hydrophilic hairy CLPAM@PNIPAm particles are believed to be potentially useful as carriers to specific target regions, e.g., cells for controlled drug delivery and other smart biomaterial applications.
- SourceAvailable from: Lance A Liotta[show abstract] [hide abstract]
ABSTRACT: Many low-abundance biomarkers for early detection of cancer and other diseases are invisible to mass spectrometry because they exist in body fluids in very low concentrations, are masked by high-abundance proteins such as albumin and immunoglobulins, and are very labile. To overcome these barriers, we created porous, buoyant, core-shell hydrogel nanoparticles containing novel high affinity reactive chemical baits for protein and peptide harvesting, concentration, and preservation in body fluids. Poly(N-isopropylacrylamide-co-acrylic acid) nanoparticles were functionalized with amino-containing dyes via zero-length cross-linking amidation reactions. Nanoparticles functionalized in the core with 17 different (12 chemically novel) molecular baits showed preferential high affinities (K(D) < 10(-11) M) for specific low-abundance protein analytes. A poly(N-isopropylacrylamide-co-vinylsulfonic acid) shell was added to the core particles. This shell chemistry selectively prevented unwanted entry of all size peptides derived from albumin without hindering the penetration of non-albumin small proteins and peptides. Proteins and peptides entered the core to be captured with high affinity by baits immobilized in the core. Nanoparticles effectively protected interleukin-6 from enzymatic degradation in sweat and increased the effective detection sensitivity of human growth hormone in human urine using multiple reaction monitoring analysis. Used in whole blood as a one-step, in-solution preprocessing step, the nanoparticles greatly enriched the concentration of low-molecular weight proteins and peptides while excluding albumin and other proteins above 30 kDa; this achieved a 10,000-fold effective amplification of the analyte concentration, enabling mass spectrometry (MS) discovery of candidate biomarkers that were previously undetectable.Journal of the American Chemical Society 11/2011; 133(47):19178-88. · 10.68 Impact Factor