Nanoporous 3D Covalent Organic Frameworks with pts Topology as Anticancer Drug Nanocarriers

Noted for their unique structural and functional attributes
including
especially high surface areas, open interconnected nanochannels, and
rich active sites, three-dimensional (3D) covalent organic frameworks
(COFs) have flourished as frontier materials for energy, environmental,
and biomedical research. However, the narrow options of 3D organic
building blocks, poor reversibility in covalent linkage formation,
and highly complicated crystal structure analysis raise several challenges
to the construction of 3D COFs for which the number of 3D COF structures
is still restricted to a few. Here, we report on the design and synthesis
strategy to develop two 3D COFs, namely, TUS-440 and TUS-441, with
2- and 3-fold interpenetrated pts topology, respectively,
by combining a Td-symmetric tetrahedral
vertex with two C2-symmetric rectangular
linkers. The resulting COFs demonstrate well-defined crystalline porous
structures and Brunauer–Emmett–Teller surface areas
of 1320 and 1016 m2 g–1, respectively.
In vitro drug delivery studies substantiate these COFs as efficient
nanocarriers with good loading and sustained release of anticancer
drugs (cytarabine and 5-fluorouracil), showing great potential for
increasing therapeutic efficacy and reducing the dosing frequency.