Stimuli-responsive molecularly imprinted hybrid polymer gel as a potential system for controlled release

Purification of Andrographolide Methanolic Extract Using Molecularly Imprinted Polymer Prepared by Precipitation Polymerization

Molecularly Imprinted Polymer (MIP) has a specific cavity in which the conformity of shape, size, and functionalities corresponds with its template molecule and has been widely used in separation processes. Therefore, this study aims to examine the application of MIP for the purification of andrographolide. The MIP was synthesized by precipitation polymerization using methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) as the functional monomer and cross-linker, andrographolide as a template, and acetonitrile:toluene (3:1) as porogen solvent. The results showed that the binding capacity of Synthesized MIP was 1.2486 mg/g, while the particle size was 295.5 nm with a polydispersity index of 0.064. Furthermore, the imprinting and selectivity factors were 1.148 and 12.37, respectively. The purification process by MIP increased the purity from 55.37 ± 0.69 to 94.94% ± 0.34, while the isolate characterization showed that purified andrographolide had a similar character compared to the standard.

Single Molecular Demonstration of Modulating Charge Inversion of DNA

Charge inversion of DNA is a counterintuitive phenomenon in which the effective charge of DNA switches its sign from negative to positive in the presence of multivalent counterions. The underlying microscopic mechanism is still controversial whether it is driven by a specific chemical affinity or electrostatic ion correlation. It is well known that DNA shows no charge inversion in normal aqueous solution of trivalent counterions though they can induce the conformational compaction of DNA. However, in the same trivalent counterion condition, we demonstrate for the first time the occurrence of DNA charge inversion by decreasing the dielectric constant of solution to make the electrophoretic mobility of DNA increase from a negative value to a positive value. In contrast, the charge inversion of DNA induced by quadrivalent counterions can be canceled out by increasing the dielectric constant of solution. The physical modulation of DNA effective charge in two ways unambiguously demonstrates that charge inversion of DNA is a predominantly electrostatic phenomenon driven by the existence of a strongly correlated liquid (SCL) of counterions at the DNA surface. This conclusion is also supported by the measurement of condensing and unraveling forces of DNA condensates by single molecular MT.