| 1. |
- Cao, Danfeng, 1991-, et al.
(author)
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Biohybrid Variable-Stiffness Soft Actuators that Self-Create Bone
- 2022
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In: Advanced Materials. - Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA. - 0935-9648 .- 1521-4095. ; 34:8
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Journal article (peer-reviewed)abstract
- Inspired by the dynamic process of initial bone development, in which a soft tissue turns into a solid load-bearing structure, the fabrication, optimization, and characterization of bioinduced variable-stiffness actuators that can morph in various shapes and change their properties from soft to rigid are hereby presented. Bilayer devices are prepared by combining the electromechanically active properties of polypyrrole with the compliant behavior of alginate gels that are uniquely functionalized with cell-derived plasma membrane nanofragments (PMNFs), previously shown to mineralize within 2 days, which promotes the mineralization in the gel layer to achieve the soft to stiff change by growing their own bone. The mineralized actuator shows an evident frozen state compared to the movement before mineralization. Next, patterned devices show programmed directional and fixated morphing. These variable-stiffness devices can wrap around and, after the PMNF-induced mineralization in and on the gel layer, adhere and integrate onto bone tissue. The developed biohybrid variable-stiffness actuators can be used in soft (micro-)robotics and as potential tools for bone repair or bone tissue engineering.
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| 2. |
- Cao, Danfeng, 1991-, et al.
(author)
-
Biohybrid Variable-Stiffness Soft Actuators that Self-Create Bone
- 2022
-
In: International conference on Electromechanically Active Polymer(EAP) transducers & artificial muscles, Tuscany, June 7-9, 2022. - : EuroEAP 2022.
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Conference paper (pop. science, debate, etc.)abstract
- We herein describe the fabrication, optimisation and characterisation of a biohybrid variable stiffness actuator that creates its own bone. By combining the electroresponsive properties of polypyrrole (PPy) with the compliant response of alginate gels functionalised with cell-derived plasma membrane nanofragments (PMNFs) it was possible to obtain bio-induced variable stiffness actuators. When the PMNFs were incubated into MEM, i.e. exposure to Ca, this caused the formation of calcium-phosphate minerals (i.e. amorphous calcium phosphate and hydroxyapatite) in the alginate gel, resulting in a more rigid layer and thus reducing and finally impeding the movement of the actuator, locking it in a fixed position within only 2 days. These actuators could morph in various, pre-programmed shapes and change their properties from soft to rigid. Adding different patterns to the actuator allowed locking the device in a predetermined shape without energy consumption, facilitating its application as soft-to-hard robotics as a biohybrid variant of so-called 4D manufacturing. The devices could wrap around and integrate into bone by the induced mineralisation in and on the gel layer. This illustrates its use as a potential tool to repair bone or in bone tissue engineering.
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| 3. |
- Cao, Danfeng, et al.
(author)
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Electrochemical control of bone microstructure on electroactive surfaces for modulation of stem cells and bone tissue engineering
- 2023
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In: Science and Technology of Advanced Materials. - : TAYLOR & FRANCIS LTD. - 1468-6996 .- 1878-5514. ; 24:1
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Journal article (peer-reviewed)abstract
- Controlling stem cell behavior at the material interface is crucial for the development of novel technologies in stem cell biology and regenerative medicine. The composition and presentation of bio-factors on a surface strongly influence the activity of stem cells. Herein, we designed an electroactive surface that mimics the initial process of trabecular bone formation, by immobilizing chondrocyte-derived plasma membrane nanofragments (PMNFs) on its surface for rapid mineralization within 2 days. Moreover, the electroactive surface was based on the conducting polymer polypyrrole (PPy), which enabled dynamic control of the presentation of PMNFs on the surface via electrochemical redox switching, further resulting in the formation of bone minerals with different morphologies. Furthermore, bone minerals with contrasting surface morphologies had differential effects on the differentiation of human bone marrow-derived stem cells (hBMSCs) cultured on the surface. Together, this electroactive surface showed multifunctional characteristics, not only allowing dynamic control of PMNF presentation but also promoting the formation of bone minerals with different morphologies within 2 days. This electroactive substrate could be valuable for more precise control of stem cell growth and differentiation, and further development of more suitable microenvironments containing bone apatite for housing a bone marrow stem cell niche, such as biochips/bone-on-chips.
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| 4. |
- Cao, Danfeng, 1991-, et al.
(author)
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Soft actuators that self-create bone for biohybrid (micro)robotics
- 2022
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In: Proceedings of The 5th International Conference on Manipulation, Automation, And Robotics at Small Scales (MARSS 2022). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665459730 - 9781665459747 ; , s. 1-6
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Conference paper (peer-reviewed)abstract
- Here we present a new class of variable stiffness actuators for soft robotics based on biohybrid materials that change their state from soft-to-hard by creating their own bones. The biohybrid variable stiffness soft actuators were fabricated by combining the electromechanically active polymer polypyrrole (PPy) with a soft substrate of polydimethylsiloxane or alginate gel. These actuators were functionalized with cell-derived plasma membrane nanofragments (PMNFs), which promote rapid mineralization within 2 days. These actuators were used in robotic devices, and PMNF mineralization resulted in the robotic devices to achieve a soft to stiff state change and thereby a decreased or stopped actuation. Moreover, perpendicularly and diagonally patterned actuators were prepared. The patterned actuators showed programmed directional actuation motion and could be fixated in this programmed state. Finally, patterned actuators that combined soft and rigid parts in one actuator showed more complex actuation motion. Together, these variable stiffness actuators could expand the range of applications of morphing robotics with more complex structures and functions.
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| 5. |
- Cao, Danfeng, et al.
(author)
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Tunable electroactive biomimetic bone-like surfaces for bone marrow-on-chips
- 2023
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In: 2023 IEEE BIOSENSORS CONFERENCE, BIOSENSORS. - : IEEE. - 9798350346046 - 9798350346114
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Conference paper (peer-reviewed)abstract
- Electro-stimulation is an effective way to manipulate the presentation of bio-factors at the materials interface. This study aimed to develop electrochemically-modified trabecular bone-like surfaces for manipulation of mesenchymal and hematopoietic cells. The electroactive surface was based on the conducting polymer polypyrrole for dynamic control of the presentation and mineralisation of chondrocyte-derived plasma membrane nanofragments (PMNFs) covalently immobilized on the surface. Electrochemical redox switching resulted in the PMNF-based formation of bone minerals with different morphologies, which further demonstrated to have distinct effects on the survival of mouse bone marrow-derived mesenchymal and hematopoietic cell populations cultured on the surface. This tunable electroactive surface could be a valuable tool for dynamically sensing and/or controlling stem cell functions in more suitable biomimetic microenvironments housing a stem cell niche.
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| 6. |
- Cao, Danfeng, et al.
(author)
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Variable Stiffness Actuators with Covalently Attached Nanofragments that Induce Mineralization
- 2023
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In: Advanced Materials Technologies. - : WILEY. - 2365-709X. ; 8:8
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Journal article (peer-reviewed)abstract
- Soft robotics has attracted great attention owing to their immense potential especially in human-robot interfaces. However, the compliant property of soft robotics alone, without stiff elements, restricts their applications under load-bearing conditions. Here, biohybrid soft actuators, that create their own bone-like rigid layer and thus alter their stiffness from soft to hard, are designed. Fabrication of the actuators is based on polydimethylsiloxane (PDMS) with an Au film to make a soft substrate onto which polypyrrole (PPy) doped with poly(4-styrenesulfonic-co-maleic acid) sodium salt (PSA) is electropolymerized. The PDMS/Au/PPy(PSA) actuator is then functionalized, chemically and physically, with plasma membrane nanofragments (PMNFs) that induce bone formation within 3 days, without using cells. The resulting stiffness change decreased the actuator displacement; yet a thin stiff layer couldnot completely stop the actuators movement, while a relatively thick segment could, but resulted in partial delamination the actuator. To overcome the delamination, an additional rough Au layer was electroplated to improve the adhesion of the PPy onto the substrate. Finally, an alginate gel functionalized with PMNFs was used to create a thicker mineral layer mimicking the collagen-apatite bone structure, which completely suppressed the actuator movement without causing any structural damage.
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