Poly-N-Isopropylacrylamide Hydrogel Based Fluoroimmunoassay of Methyltestosterone

A novel immunoassay method for methyltestosterone (MT) in serum ovas developed.The antigen of MT (Ag(MT))was synthesized by covalently bonding MT to BSA and raising its antibody (Ab(MT)). Ab(MT) was con.jugated to poly-N-isopropylacrylamide (p-NIPAAm) to form Ab(MT) bound thermally reversible hydrogel p-NIPAAm-Ab((MT) A competitive immunoassay method based on the competition of fluorescein isothiocyanate (FITC) labeled MT antigen (FITC-Ag(MT)) and free MT with limited amount of p-NIPAAm-Ab(MT) was established. The separation in the assay process was achieved by precipitation of the immuno-complex above its critical solution temperature. The detection limit for MT is 50ng/ml. The recoveries of MT from human serum are satisfactory.

Programming molecular switches in water and ethanol via thermo-sensitive polymers for phase control in energetic crystals

The practical application of energetic materials, particularly 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20), is frequently impeded by phase transition challenges. In this study, we propose a novel strategy to enhance the stability of CL-20 by employing a thermo-sensitive polymer,poly(N-isopropylacrylamide)(PNIPAM), to modulate its phase transitions. Our approach involves the use of an in-situ polymerized polydopamine(PDA) shell as a platform for surface grafting through atom transfer radical polymerization, yielding a core-shell structured CL-20@PDA-PNIPAM. Through comprehensive characterization, the successful grafting of PNIPAM is confirmed, significantly enhanced the phase stability of CL-20. Notably, our core-shell structure exhibits a 13℃ increase in phase transition temperature compared to raw CL-20, thereby delaying the ε→a phase transition by over 80 min under combined thermal and solvent conditions. The enhanced stability is attributed to the hydrophobic nature of PNIPAM above its low critical solution temperature in water, which effectively shields the CL-20 crystal. These findings provide new insights into enhancing the stability and safety of energetic materials in complex environments, highlighting the potential of our molecular switch mechanism.

Finite deformation swelling of a temperature-sensitive hydrogel cylinder under combined extension-torsion

The swelling behavior of a temperature-sensitive poly-N-isopropylacrylamide(PNIPAM) hydrogel circular cylinder is studied subjected to combined extension-torsion and varied temperature. In this regard, a semi-analytical solution is proposed for general combined loading. A finite element(FE) analysis is conducted, subjecting a hydrogel cylinder to the combined extension-torsion and the varied temperature to evaluate the validity and accuracy of the solution. A user-defined UHYPER subroutine is developed and verified under free and constrained swelling conditions. The FE results illustrate excellent agreement with the semi-analytical solution. Due to the complexity of the problem, some compositions and applied loading factors are analyzed. It is revealed that for larger cross-linked density and larger ending temperature, the cylinder yields higher stresses and smaller radial swelling deformation. Besides, the radial and hoop stresses increase by applying larger twist and axial stretch. The hoop stresses intersect at approximately R/Rout = 0.58, where the hoop stress vanishes. Besides, the axial force has direct and inverse relationships with the axial stretch and the twist, respectively. However, the resultant torsional moment behavior is complex, and the position of the maximum point varies significantly by altering the axial stretch and the twist.