Temperature-responsive Pickering high internal phase emulsions for recyclable efficient interfacial biocatalysis

Ultrasound-assisted intensification of Pickering interfacial biocatalysis preparation of vitamin A aliphatic esters

A novel approach to ultrasound-assisted Pickering interfacial biocatalysis (PIB) has been proposed and implemented for the efficient enzymatic transesterification production of vitamin A fatty acid esters. This is the first instance of exploiting the synergistic effect of ultrasound and the bifunctional modification of enzyme supports to accelerate biocatalytic performance in PIB systems. The optimal conditions were determined to be ultrasound power of 70 W, on/off time of 5 s/5 s, substrate molar ratio of 1:1, enzyme addition of 2 %, and a volume ratio of n-hexane to PBS of 3:1, a temperature of 40 °C, and a time of 30 min. The application of ultrasound technology not only improved lipase activity but also allowed for a reduction in emulsion droplet size to enhance interfacial mass transfer.Bifunctional modification of silica-based supports enhanced stability of immobilized enzymes by increasing hydrogen bonding while maintaining the active interface microenvironment. Compared with a non-ultrasound-assisted PIB system stabilized by mono-modified immobilized enzyme particles, the catalytic efficacy (CE) of the novel system reached 8.18 mmol g-1 min-1, which was enhanced by 3.33-fold, while the interfacial area was found to have increased by 17.5-fold. The results facilitated the conversion of vitamin A palmitate (VAP), vitamin A oleate (VAO), vitamin A linoleate (VAL), and vitamin A linolenate (VALn), with conversion rates of approximately 98.2 %, 97.4 %, 96.1 %, and 94.7 %, respectively. This represents the most efficient example that has been reported to our knowledge. Furthermore, the system demonstrated improved reusability, with a conversion rate of 62.1 % maintained even after 10 cycles. The findings presented in this paper provide valuable insights into an efficient and conveniently promising protocol for the development of PIB systems.

Pickering emulsion biocatalysis: Bridging interfacial design with enzymatic reactions

Non-homogeneous enzyme-catalyzed systems are more widely used than homogeneous systems. Distinguished from the conventional biphasic approach, Pickering emulsion stabilized by ultrafine solid particles opens up an innovative platform for biocatalysis. Their vast specific surface area significantly enhances enzyme-substrate interactions, dramatically increasing catalytic efficiency. This review comprehensively explores various aspects of Pickering emulsion biocatalysis, provides insights into the multiple types and mechanisms of its catalysis, and offers strategies for material design, enzyme immobilization, emulsion formation control, and reactor design. Characterization methods are summarized for the determination of drop size, emulsion type, interface morphology, and emulsion potential. Furthermore, recent reports on the design of stimuli-responsive reaction systems are reviewed, enabling the simple control of demulsification. Moreover, the review explores applications of Pickering emulsion in single-step, cascade, and continuous flow reactions and outlines the challenges and future directions for the field. Overall, we provide a review focusing on Pickering emulsions catalysis, which can draw the attention of researchers in the field of catalytic system design, further empowering next-generation bioprocessing.

New Approach for Preparation of Porous Polymers with Reversible Pore Structures for a Highly Safe Smart Supercapacitor

Porous polymers have many industrial applications, but their pore structures (open or closed) are usually fixed during polymerization. In this study, polymers with reversible and controllable pore structures, namely, thermosensitive porous hydrogels with regulated volume phase transition temperature, were prepared using a Pickering high-internal-phase emulsion as the template. Upon heating, the hydrogels transformed not only in their wettability (between hydrophilicity and hydrophobicity with water contact angles of 21.8 and 100.9°) but also their pore structure (between open through-holes and closed holes with pore throat sizes of 15.58 and 0 μm, respectively) in a short time (<10 s). When the hydrogel was used as a separator in smart supercapacitors (SCs), this behavior effectively limited the path of electrolyte migration, reducing the chance of conflagration accidents. Moreover, by utilizing the highly reversible pore structures and wettability of the porous hydrogel, reversible charging and discharging were restored after the system cooled down. This work not only provides great guidance for preparing porous polymers with reversible pore structures but also paves the way for designing smart SCs with enhanced safety.

Effective pickering emulsifiers based on submicron carboxymethyl cellulose/chitosan polymer particles

In this study, cross-linked carboxymethyl cellulose/chitosan submicron particles were employed to facilitate the stabilization of Pickering emulsion. The polymer particles were prepared using the polyelectrolyte self-assembly method in conjunction with isocyanide based multicomponent reactions and the characteristics were obtained using: nuclear magnetic resonance, Fourier-transform infrared spectroscopy and dynamic light scattering. Atomic force microscopy revealed the heterogeneous structure of the resulting submicron particles with domains of 20-30 nm in size. The average diameter was found to be in the range of 229-378 nm and they were found to be suitable for the fabrication of oil/water Pickering emulsion when proceeded via the homogenization method followed by sonication. The results obtained revealed that carboxymethyl cellulose/chitosan particles significantly stabilized the droplets at the oil/water interface. Even at low particle concentrations of 0.3 g/L (which is close to that of low molecular weight surfactants) stable Pickering emulsions have been obtained. Additionally, the resulting emulsions showed a high level of stability with regard to changes in pH, temperature and ionic strength. The natural alkaloid piperine was used as a model compound to load the resulting particles, which possessed encapsulation efficiency of 90.6±0.4%. Furthermore, the in vitro release profile of piperine from the Pickering emulsion revealed a much-controlled release in both acidic and neutral media as compared to the unformulated piperine. Additional findings in this work revealed important information on the application of carboxymethyl cellulose/chitosan submicron particles as Pickering stabilizers for creation of new delivery systems.

Pd NP-loaded covalent organic framework for pH-switched Pickering emulsion catalytic dechlorination

Quinoline carboxylic acid-linked and Pd nanoparticle (NP)-loaded COF nanospheres were constructed via a three-component one-pot Doebner reaction and post-synthetic metalation. The obtained Pd@DhaTAPB-COOH solid stabilizer can greatly promote the pH-switched recyclable Pickering interfacial dechlorination reaction, which sheds light on the bright future of smart Pickering emulsion catalysis.

Fabrication of double imprinted anchor points in cellulose nanocrystals-based hierarchical porous polyHIPEs for selective separation of flavoniods under physiological pH

Previous research had proved that molecular imprinted polymers can be used as separation material for removing Naringin (NRG) from agricultural pomelo wastes effectively. But the adsorption amounts of NRG molecules from traditional MIPs was quite low by using boronic acid as functional monomer because of single affinity interaction. Therefore, we developed the new combination of bifunctional monomers (i.e. low pKa boronate affinity monomer 2,4-difluoro-3-formylphenylboronic acid and dopamine) based on cellulose nanocrystals (CNCs) mixed with polymerized high internal phase emulsion (polyHIPE, PH) through an double layer surface imprinted method. The introduction of polyethylenimine (PEI) can offer abundant anchor units for the growth of more anchor sites to immobilization template molecules. Importantly, largely improved selective adsorption amounts (50.79 μmol g-1), which may be attribute to the fabrication of the uniform growth of double imprinted layers onto the polydopamine (PDA)/boronic acid-based surfaces. In addition, the resulting double recognition molecular imprinted polymers (MIPs) based on hypercrosslinked PH (DR-HCLPH@MIPs) not only exhibited fast adsorption kinetic of NRG molecule, but also possessed excellent selectivity and high adsorption capacities at physiological pH. Meanwhile, the coarse NRG from pomelo waste can be high selectively extracted to 94.74%. Overall, this study provides a versatile approach for fabrication of the sandwich-biscuit-like double imprinting layer porous MIPs for precise identification and ultrafast transport separation of NRG from complex samples.

CO2 responsive self-standing Pickering emulsion gel stabilized with rosin-based surfactant modified cellulose nanofibrils

Emulsion gel was developed to provide desirable texture, palatability and functionality to food products. Tunable stability of emulsions is often desired, as in certain situations, the chemical content release usually relies on emulsion induced destabilization of the droplet. However, the destabilization for emulsion gel is difficult because of the formation of highly entangled networks. To address this issue, a fully biobased Pickering emulsion gel stabilized by cellulose nanofibrils (CNF) modified with a CO2 responsive rosin-based surfactant, maleopimaric acid glycidyl methacrylate ester 3-dimethylaminopropylamine imide (MPAGN) was reported. The emulsification/de-emulsification can be reversibly regulated because this surfactant has sensitive CO2 responsive property. MPAGN can be reversibly between active cationic (MPAGNH+) and inactive nonionic (MPAGN) responsive to CO2 and N2. The microstructure of the emulsion gel was observed and compared before and after the response. The rheological properties of emulsion gel stabilized by different concentrations of MPAGNH+ and different contents of CNF were studied separately. As 0.2 wt% CNF was dispersed in 1 mM MPAGNH+ solution, the obtained emulsion can be self-standing for long duration. The rheology study indicated that these emulsions show typical gel characteristics with shear-thinning behavior. The stabilization mechanism of these gel emulsion is a synergistic effect caused by the combination of CO2 responsive Pickering emulsion and intertwined network caused by the hydrogen-bond interaction among CNF.