Ionization-Induced Reversible Aggregation of Self-Assembled Polycarbonyl Hydrazide Nanoparticles: A Potential Candidate for Turn-On Base Sensor and pH-Switchable Materials

Hierarchical assembly of nanostructures remains one of the desirable targets in nanoscience. Herewith, we report a hydrogen-bond-promoted polymeric nanoparticle (NP) system that reversibly aggregates into different microstructures upon variation of the concentration of the base in the medium. Polycarbonyl hydrazide, a polyaza-Michael adduct, formed uniform spherical NPs in solution owing to the presence of inherent CO---HNCO hydrogen-bond-based physical cross-links in the system. In the presence of the base, the CONH groups ionized to form the corresponding nitranions, and the resulting anion−π interaction between the ionic polymer NPs promoted the secondary aggregation to different shapes and sizes in the microdomain. The shape of the aggregated microparticles gradually changed from spherical to fiber through flakes upon a gradual increase in the base concentration in the medium. The modulus of these superstructures notably decreased compared to that of the original un-ionized NPs, suggesting the involvement of anion−π interaction and loss of hydrogen bonding in the system. Importantly, these dynamic shape changes in the submicron range were reversible, and the addition of a protic solvent or acid recovered the original shape and size. PBTH in sufficiently low concentration (40 μg/mL) is capable of detecting various organic and inorganic bases in the ppm level and pH values between 8.4 and 11.4 with 1.0 precision. The polymer is also a promising candidate for pH-switchable applications

Expression levels of twelve defense genes up-regulated on insect attack.

<p>The expression levels were obtained by normalization with black gram EF1<i>α</i> gene. Expression analysis were done in two stages, control and oviposition after 7 days for (A) DEF (Defensin), (B) DRT (DNA damage repair toleration protein), (C) LOX (Lipoxygenase), D: PR (Pathogenesis related protein), (E) HYP48 (Hypothetical protein), (F) DRE (Dehydration responsive element transcription factor), (G) HSPIV (Heat shock protein), (H) HSP70 (Heat shock protein), (I) LT (low temperature induced protein), (J) DEH (Dehydrin), (K) MAPK (Mitogen activated protein kinase), (L) RSTK (serine threonine kinase like receptor). Bars represent mean ± standard deviation. * P value< 0.05, as determined by paired two-tailed student’s t- tests.</p

Functional categorization of GO terms.

<p>GO terms were distributed into (A) Biological function (B) Molecular Function (C) Cellular Component.</p

BLAST species level distribution of unigenes.

<p>Number of BLAST hits retrieved from NCBI databases. The majority of BLAST hits represents similarity with <i>Glycine max</i>, <i>Vigna angularis and Vigna radiata</i>.</p

Differentially expressed ESTs after grouping into various functional categories.

<p>The horizontal bars represent percentage share of ESTs in the subtractive library.</p

The pie chart represents sub-categories for “Response to stimulus” and their respective abundance in the SSH library under the biological process category.

<p>The pie chart represents sub-categories for “Response to stimulus” and their respective abundance in the SSH library under the biological process category.</p

Bruchid egg induced transcript dynamics in developing seeds of black gram (<i>Vigna mungo</i>) - Fig 1

<p>ROS accumulation in: A. Control pods of the mild tolerant plant. B. Oviposited pods of the mild tolerant plant after 7 days.</p

An overview of unigene statistics.

<p>An overview of unigene statistics.</p