One-step preparation of molecularly imprinted hollow beads for pseudohypericin separation from Hypericum perforatum L. extracts

A Note about Crosslinking Density in Imprinting Polymerization

Imprinting polymerization is an exciting technique since it leads to specific binding sites, which are the basis of a variety of applications, such as sensors, detectors, and catalysts. The specific binding sites are created using templates and then fixing the structure of the binding site with crosslinking. The literature review of imprinting polymerizations shows that the crosslinking density governs the physical properties of the resulting molecularly imprinted polymer (MIP). It is also a factor governing the capacity and the selectivity of MIPs. Reviewing polymer science data and theory, the crosslinking density commonly used in MIP synthesis is unusually high. The data reviewed here suggest that more research is needed to determine the optimal crosslinking density for MIPs.

Molecular Imprinting: Green Perspectives and Strategies

Advances in revolutionary technologies pose new challenges for human life; in response to them, global responsibility is pushing modern technologies toward greener pathways. Molecular imprinting technology (MIT) is a multidisciplinary mimic technology simulating the specific binding principle of enzymes to substrates or antigens to antibodies; along with its rapid progress and wide applications, MIT faces the challenge of complying with green sustainable development requirements. With the identification of environmental risks associated with unsustainable MIT, a new aspect of MIT, termed green MIT, has emerged and developed. However, so far, no clear definition has been provided to appraise green MIT. Herein, the implementation process of green chemistry in MIT is demonstrated and a mnemonic device in the form of an acronym, GREENIFICATION, is proposed to present the green MIT principles. The entire greenificated imprinting process is surveyed, including element choice, polymerization implementation, energy input, imprinting strategies, waste treatment, and recovery, as well as the impacts of these processes on operator health and the environment. Moreover, assistance of upgraded instrumentation in deploying greener goals is considered. Finally, future perspectives are presented to provide a more complete picture of the greenificated MIT road map and to pave the way for further development.

Role of Functional Monomers upon the Properties of Bisphenol A Molecularly Imprinted Silica Films

In this study, two types of bisphenol A molecularly imprinted films (BPA-MIP) were successfully prepared via sol-gel derived methods using two different organosilane functional monomers N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (DAMO-T) or (3-mercaptopropyl)trimethoxysilane (MPTES). The physical-chemical characterization of films, in terms of morphology, structure, thermal analysis, and optical features, suggested that thinner films with a homogenous porous structure were more likely to retain BPA molecules. The MIP films revealed the rapid and quantitative adsorption of BPA, registering the most specific binding in the first five minutes of contact with the BPA-MIP film. Silica films were effectively regenerated for further usage for at least five times, demonstrating their high stability and reusability. Even if the performance of films for BPA uptake dropped dramatically after the third adsorption/reconditioning cycle, this synthesis method for BPA-MIP films has proven to be a reliable and cheap way to prepare sensitive films with potential application for re-usable optical sensors.

Biomimetic Sensitive Elements for 2,4,6-Trinitrotoluene Tested on Multi-Layered Sensors

In spite of technological progress, most of the current techniques for 2,4,6-trinitrotoluene (TNT) detection are time consuming due to laborious sensor preparation. Thereby, the aim of this work was to enlarge the knowledge for preparing sensitive elements for TNT with the aid of molecular imprinting; a known technique used to deliver biomimetic materials. The study first depicts the auto-assembly mechanism of (TNT) with functional diamino-silanes (i.e., N-(2-aminoethyl)-3-aminopropyl methyl dimethoxysilane), via “double” Meisenheimer complexes. This mechanism is being described herein for the first time and applied further to obtain molecularly imprinted polymer (MIP) films for TNT recognition. For testing the potential application of films as chemical sensor elements, typical rebinding assays of TNT in a liquid state and the rebinding of TNT in a vapor state, using multilayered sensor chips composed of quartz-chromium (Cr)-gold (Au)-titanium oxide (TiO2), were employed. Batch rebinding experiments have shown that thinner films were more efficient on retaining TNT molecules in the first five min, with a specificity of about 1.90. The quartz-Cr-Au-TiO2-MIP capacitive sensors, tested in vapor state, registered short response times (less than 25 s), low sensitivity to humidity and high specificity for TNT.

Straightforward Preparation of Naphtodianthrone-Rich Ethanolic Extracts from Wild St. John's Wort

Separation of naphtodianthrones (NTs) from Hypericum perforatum L. (aerial part of St. John's Wort) is still topical due to some hard-to-beat medicinal attributes of these bioactive compounds. Unfortunately, their low bioavailability (0.06%-0.4%) complicates the extraction process. Therefore, developing straightforward and lower-cost methodologies for NT separation is still a priority. In support of this purpose, for preparing NT formulations from flowers and leaves of wild St. John's Wort (hyperici herba), a cutoff preparative methodology is described herein. Combining Soxhlet extraction and reflux extraction, some concentrated and rather pure NT ethanolic-based formulations without chlorophyl and grease were obtained.