Longitudinal Study of the Effects of Environmental pH on the Mechanical Properties of Aspergillus niger

Tuning Microcapsule Shell Thickness and Structure with Silk Fibroin and Nanoparticles for Sustained Release

Microcapsules have attracted widespread interest for their unique properties in encapsulation, protection, and separation of active ingredients from the surrounding environment. However, microcapsule carriers with controllable shell thickness, permeability, good mechanical properties, and thermostability are challenging to obtain. Herein, robust and versatile composite microcapsules were fabricated using SiO₂ nanoparticle-stabilized (Pickering) oil emulsions as core templates, while silk fibroin (SF) was assembled at the oil/water interface. This process resulted in the formation of physically and chemically stable microcapsules with a thick (∼800 nm) shell that protected the encapsulated ingredient from high shear forces and high temperatures during spray-drying. SiO₂ nanoparticles were randomly distributed in the shell matrix after preparation, making the microcapsules mechanically robust (4.48 times higher than control samples prepared using surfactant Tween 80 instead of the SiO₂ nanoparticles), as well as thermostable (retained shape to 900 °C). The microcapsules displayed tunable drug release by adjusting the SF content in the shell. Under optimal conditions (weight ratio of SiO₂/SF = 7:10, corn oil content about 55 wt %), a model drug (curcumin) was encapsulated in the SF microcapsules with an encapsulation efficiency up to 95%. The in vitro drug release from these SF microcapsules lasted longer than control microcapsules, demonstrating the capability of these novel microcapsules in sustaining drug release.

Lead immobilization assisted by fungal decomposition of organophosphate under various pH values

Organic phosphates (OP) account for approximately 30-90% of total soil P. However, it is too stable to be utilized by plants as available P source. Aspergillus niger (A. niger) has considerable ability to secret phytase to decompose OP. Meanwhile, mineralization of lead (Pb) is efficient to achieve its remediation. This study hence investigated Pb immobilization by A. niger assisted decomposition of OP under variable acidic environments. A. niger can survive in the acidic environment as low as pH = 1.5. However, alternation of environmental pH within 3.5-6.5 significantly changed fungal phytase secretion. In particular, weakly acidic stimulation (pH of ~5.5) increased phytase activity secreted by A. niger to 0.075 µmol/min/mL, hence elevating P release to a maximal concentration of ~20 mg/L. After Pb addition, ATR-IR and TEM results demonstrated the formation of abundant chloropyromorphite [Pb5(PO4)3Cl] mineral on the surface of mycelium at pH = 5.5. Anglesite, with a higher solubility than pyromorphite, was precipitated massively in other treatments with pH lower or higher than 5.5. This study elucidated the great potential of applying OP for Pb immobilization in contaminated water.

Integrated Multiscale Biomaterials Experiment and Modeling

The integration of modeling and experimentation is an integral component of all engineering design. Developing the technologies to achieve this represents a critical challenge in biomaterials because of the hierarchical structures that comprise them and the spectra of timescales upon which they operate. Progress in integrating modeling and experiment in biomaterials represents progress towards harnessing them for engineering application. We present here a summary of the state of the art, and outlooks for the field as a whole.