Enzyme‐Decorated Covalent Organic Frameworks as Nanoporous Platforms for Heterogeneous Biocatalysis

Abstract

Sustainability in chemistry heavily relies on heterogeneous catalysis. Enzymes, the main catalyst for biochemical reactions in nature, are an elegant choice to catalyze reactions due to their high activity and selectivity, although they usually suffer from lack of robustness. To overcome this drawback, enzyme‐decorated nanoporous heterogeneous catalysts were developed. Three different approaches for Candida antarctica lipase B (CAL‐B) immobilization on a covalent organic framework (PPF‐2) were employed: physical adsorption on the surface, covalent attachment of the enzyme in functional groups on the surface and covalent attachment into a linker added post‐synthesis. The influence of the immobilization strategy on the enzyme uptake, specific activity, thermal stability, and the possibility of its use through multiple cycles was explored. High specific activities were observed for PPF‐2‐supported CAL‐B in the esterification of oleic acid with ethanol, ranging from 58 to 283 U mg−1, which was 2.6 to 12.7 times greater than the observed for the commercial Novozyme 435.

In vivo oral insulin delivery via covalent organic frameworks

“…It is anticipated that upon loading with insulin, the periodicity in the TTA-DFP-nCOF layers is affected to accommodate insulin molecules, thus losing crystallinity. [57][58][59][60] When the TTA-DFP-nCOF was loaded with a reduced quantity of insulin (30% loading capacity, ESI †), the PXRD pattern showed the presence of 2q ¼ 4.9 and 25.6 peaks, although their intensities decreased signicantly compared to those of the pristine nCOF, conrming our hypothesis. The uniformity of TTA-DFP-nCOF/insulin is evident from AFM analysis and increased to 12 nm upon insulin encapsulation compared to that of the pristine nCOF (Fig.…”

Nanoscale covalent organic frameworks as theranostic platforms for oncotherapy: synthesis, functionalization, and applications

“…Host-guest encapsulation is a versatile and effective modication strategy to endow COFs with more functions, which utilizes accessible and permanent pores of COFs to capture guest molecules, including a variety of functional inorganic molecules, [382][383][384][385][386] organic molecules, [387][388][389] and even biological macromolecules. [390][391][392][393] The structural basis of host-guest encapsulation is the pores of COFs, which have unique characteristics. 394,395 First, the pores of COFs have a precise polygonal reticular structure with well-dened angles.…”

“…Due to the large and regular pores of COFs, the controlled loading and release of enzymes on the COF platform allows the enzyme to remain viable under harsh environmental conditions, which is imperative for enzyme catalysis and undoubtedly expands the application ranges of the enzymes. 392,393 Meanwhile, the chemical modication of the pore walls of COFs can easily regulate the pore environment, thereby improving the interaction and compatibility of COFs with specic enzymes, as well as optimizing the orientation of the active sites of the enzyme, thereby further improving the catalytic activity of the enzymes. 391…”

Enzyme Immobilization in Covalent Organic Frameworks: Strategies and Applications in Biocatalysis

“…Furthermore, the high porosity found in many COFs offers process throughput outperformance when compared to other micro/nanoparticles, since a higher biocatalyst amount can be immobilized per unitary mass of support . The integration of enzymes and COFs may occur via different possibilities, which include: physical adsorption and covalent attachment directly between them or via a linker molecule …”

“…In a contribution of our research group, an imine‐linked covalent organic framework (PPF‐2), was employed as a platform for CAL−B immobilization. PPF‐2 is prepared through the reaction between the tetrahedral building block tetrakis‐(4‐aminophenyl)‐methane (TTA) and the trigonal planar 1,3,5‐triformylphloroglucinol (TFP) .…”