Water-responsive 4D printing based on self-assembly of hydrophobic protein "Zein" for the control of degradation rate and drug release.

Four-dimensional (4D) printing is a promising technology that provides solutions for compelling needs in various fields. Most of the reported 4D printed systems are based on the temporal shape transformation of printed subjects. Induction of temporal heterogenicity in functions in addition to shape may extend the scope of 4D printing. Herein, we report a 4D printing approach using plant protein (zein) gel inspired by the amyloid fibrils formation mechanism. The printing of zein gel in a specialized layered-Carbopol supporting bath with different water concentrations in an ethanol-water mixture modulates hydrophobic and hydrogen bonding that causes temporal changes in functions. The part of the construct printed in a supporting bath with higher water content exhibits higher drug loading, faster drug release and degradation than those printed in the supporting bath with lower water content. Tri-segment conduit and butterfly-shaped construct with two asymmetrical wings are printed using this system to evaluate biomedical function as nerve conduit and drug delivery system. 4D printed conduits are also effective as a drug-eluting urethral stent in the porcine model. Overall, this study extends the concept of 4D printing beyond shape transformation and presents an approach of fabricating specialized baths for 4D printing that can also be extended to other materials to obtain 4D printed medical devices with translational potential.

Reversible Structural Transformation of CuI-TbIII Heterometallic MOFs with Highly Efficient Detection Capability toward Penicillin.

A CuI-TbIII heterometallic MOF, namely 1·DMF, was obtained via a coordination assembly process of isonicotinic acid with CuI and TbIII. 1·DMF can be switched to 1·MeOH in methanol with a luminescent emission response. Meanwhile, 1·MeOH exhibits a reversible single-crystal transformation to 1·DMF after immersion in DMF. Both MOFs have superior physicochemical stability. The 1·DMF-based biosensor has a remarkable sensing performance toward penicillin.

Enhancement of mechanical strength of TCP-alginate based bioprinted constructs.

To overcome the mechanical drawback of bioink, we proposed a supporter model to enhance the mechanical strength of bioprinted 3D constructs, in which a unit-assembly idea was involved. Based on Computed Tomography images of critical-sized rabbit bone defect, the 3D re-construction was accomplished by a sequenced process using Mimics 17.0, BioCAM and BioCAD software. 3D constructs were bioprinted using polycaprolactone (PCL) ink for the outer supporter under extrusion mode, and cell-laden tricalcium phosphate (TCP)/alginate bioink for the inner filler under air pressure dispensing mode. The relationship of viscosity of bioinks, 3D bioprinting pressure, TCP/alginate ratio and cell survival were investigated by the shear viscosities analysis, live/dead cell test and cell-counting kit 8 measurement. The viscosity of bioinks at 1.0 s-1-shear rate could be adjusted within the range of 1.75 ±â€¯0.29 Pa·s to 155.65 ±â€¯10.86 Pa·s by changing alginate concentration, corresponding to 10 kPa-130 kPa of printing pressure. This design with PCL supporter could significantly enhance the compressive strength and compressive modulus of standardized 3D mechanical testing specimens up to 2.15 ±â€¯0.14 MPa to 2.58 ±â€¯0.09 MPa, and 42.83 ±â€¯4.75 MPa to 53.12 ±â€¯1.19 MPa, respectively. Cells could maintain the high viability (over 80%) under the given printing pressure but cell viability declined with the increase of TCP content. Cell survival after experiencing 7 days of cell culture could be achieved when the ratio of TCP/alginate was 1 : 4. All data supported the feasibility of the supporter and unit-assembly model to enhance mechanical properties of bioprinted 3D constructs.

A Double-Walled Bimetal-Organic Framework for Antibiotics Sensing and Size-Selective Catalysis.

The first double-walled bimetal-organic framework [Cd4K4(TADA)4(H2O)12]·6DMF (1, TADA = 3,3'-((6-hydroxy-1,3,5-triazine-2,4-diyl)bis(azanediyl)) dibenzoate) has been successfully constructed. In virtue of its high porosity and abundant basic sites, MOF 1 can be served as a high-efficiently size-selective heterogeneous catalyst for Knovenagel condensation reaction. Remarkably, 1 also exhibits excellent luminescent detectability for metronidazole (MDZ) with the highest quenching constant ( Ksv) of 1.16 × 105 M-1. The results demonstrate that 1 can be served as a unique bifunctional platform for antibiotics sensing and size-selective catalysis.