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Zhao Z, Chua HM, Goh BHR, Lai HY, Tan SJ, Moay ZK, Setyawati MI, Ng KW. Anisotropic hair keratin-dopamine composite scaffolds exhibit strain-stiffening properties. J Biomed Mater Res A 2021; 110:92-104. [PMID: 34254735 DOI: 10.1002/jbm.a.37268] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 06/19/2021] [Accepted: 06/29/2021] [Indexed: 11/06/2022]
Abstract
Human hair keratin (HHK) has been successfully explored as raw materials for three-dimensional scaffolds for soft tissue regeneration due to its excellent biocompatibility and bioactivity. However, none of the reported HHK based scaffolds is able to replicate the strain-stiffening capacity of living tissues when responding to large deformations. In the present study, strain-stiffening property was achieved in scaffolds fabricated from HHK via a synergistic effect of well-defined, aligned microstructure and chemical crosslinking. Directed ice-templating method was used to fabricate HHK-based scaffolds with highly aligned (anisotropic) microstructure while oxidized dopamine (ODA) was used to crosslink covalently to HHKs. The resultant HHK-ODA scaffolds exhibited strain-stiffening behavior characterized by the increased gradient of the stress-strain curve after the yield point. Both ultimate tensile strength and the elongation at break were enhanced significantly (~700 kPa, ~170%) in comparison to that of HHK scaffolds lacking of aligned microstructure or ODA crosslinking. In vitro cell culture studies indicated that HHK-ODA scaffolds successfully supported human dermal fibroblasts (HDFs) adhesion, spreading and proliferation. Moreover, anisotropic HHK-ODA scaffolds guided cell growth in alignment with the defined microstructure as shown by the highly organized cytoskeletal networks and nuclei distribution. The findings suggest that HHK-ODA scaffolds, with strain-stiffening properties, biocompatibility and bioactivity, have the potential to be applied as biomimetic matrices for soft tissue regeneration.
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Affiliation(s)
- Zhitong Zhao
- School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | - Huei Min Chua
- School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | - Bernice Huan Rong Goh
- School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | - Hui Ying Lai
- School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | - Shao Jie Tan
- School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | - Zi Kuang Moay
- School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | | | - Kee Woei Ng
- School of Materials Science and Engineering, Nanyang Technological University, Singapore.,Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health, Harvard University, Boston, Massachusetts, USA.,Environmental Chemistry and Materials Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore.,Skin Research Institute of Singapore, Biomedical Science Institutes, Singapore
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Zhao Z, Moay ZK, Lai HY, Goh BHR, Chua HM, Setyawati MI, Ng KW. Characterization of Anisotropic Human Hair Keratin Scaffolds Fabricated via Directed Ice Templating. Macromol Biosci 2020; 21:e2000314. [PMID: 33146949 DOI: 10.1002/mabi.202000314] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/12/2020] [Indexed: 01/18/2023]
Abstract
Human hair keratin (HHK) is successfully exploited as raw materials for 3D scaffolds for soft tissue regeneration owing to its excellent biocompatibility and bioactivity. However, most HHK scaffolds are not able to achieve the anisotropic mechanical properties of soft tissues such as tendons and ligaments due to lack of tunable, well-defined microstructures. In this study, directed ice templating method is used to fabricate anisotropic HHK scaffolds that are characterized by aligned pores (channels) in between keratin layers in the longitudinal plane. In contrast, pores in the transverse plane maintain a homogenous rounded morphology. Channel widths throughout the scaffolds range from ≈5 to ≈15 µm and are tunable by varying the freezing temperature. In comparison with HHK scaffolds with random, isotropic pore structures, the tensile strength of anisotropic HHK scaffolds is enhanced significantly by up to fourfolds (≈200 to ≈800 kPa) when the tensile load is applied in the direction parallel to the aligned pores. In vitro results demonstrate that the anisotropic HHK scaffolds are able to support human dermal fibroblast adhesion, spreading, and proliferation. The findings suggest that HHK scaffolds with well-defined, aligned microstructure hold promise as templates for soft tissues regeneration by mimicking their anisotropic properties.
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Affiliation(s)
- Zhitong Zhao
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Zi Kuang Moay
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Hui Ying Lai
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Bernice Huan Rong Goh
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Huei Min Chua
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Magdiel Inggrid Setyawati
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Kee Woei Ng
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore.,Center for Nanotechnology and NanotoxicologyHarvard T.H. Chan School of Public Health, Harvard University, 665 Huntington Avenue, Boston, MA, 02115, USA.,Environmental Chemistry and Materials CentreNanyang Environment and Water Research Institution, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore, 637141, Singapore.,Skin Research Institute of Singapore, Biomedical Science Institutes, Immunos, 8A Biomedical Grove, Singapore, 138648, Singapore
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Setyawati MI, Singh D, Krishnan SPR, Huang X, Wang M, Jia S, Goh BHR, Ho CG, Yusoff R, Kathawala MH, Poh TY, Ali NABM, Chotirmall SH, Aitken RJ, Riediker M, Christiani DC, Fang M, Bello D, Demokritou P, Ng KW. Occupational Inhalation Exposures to Nanoparticles at Six Singapore Printing Centers. Environ Sci Technol 2020; 54:2389-2400. [PMID: 31967798 DOI: 10.1021/acs.est.9b06984] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Laser printers emit high levels of nanoparticles (PM0.1) during operation. Although it is well established that toners contain multiple engineered nanomaterials (ENMs), little is known about inhalation exposures to these nanoparticles and work practices in printing centers. In this report, we present a comprehensive inhalation exposure assessment of indoor microenvironments at six commercial printing centers in Singapore, the first such assessment outside of the United States, using real-time personal and stationary monitors, time-integrated instrumentation, and multiple analytical methods. Extensive presence of ENMs, including titanium dioxide, iron oxide, and silica, was detected in toners and in airborne particles collected from all six centers studied. We document high transient exposures to emitted nanoparticles (peaks of ∼500 000 particles/cm3, lung-deposited surface area of up to 220 μm2/cm3, and PM0.1 up to 16 μg/m3) with complex PM0.1 chemistry that included 40-60 wt % organic carbon, 10-15 wt % elemental carbon, and 14 wt % trace elements. We also record 271.6-474.9 pmol/mg of Environmental Protection Agency-priority polycyclic aromatic hydrocarbons. These findings highlight the potentially high occupational inhalation exposures to nanoparticles with complex compositions resulting from widespread usage of nano-enabled toners in the printing industry, as well as inadequate ENM-specific exposure control measures in these settings.
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Affiliation(s)
- Magdiel I Setyawati
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Dilpreet Singh
- Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health , Harvard University , 665 Huntington Avenue , Boston , Massachusetts 02115 , United States
| | - Sriram P R Krishnan
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
- IOM Singapore , 237 Alexandra Road , 159929 , Singapore
| | - Xian Huang
- IOM Singapore , 237 Alexandra Road , 159929 , Singapore
| | - Mengjing Wang
- School of Civil and Environmental Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Shenglan Jia
- School of Civil and Environmental Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Bernice Huan Rong Goh
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Chin Guan Ho
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Ridhwan Yusoff
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Mustafa H Kathawala
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Tuang Yeow Poh
- Lee Kong Chian School of Medicine , Nanyang Technological University , 11 Mandalay Road , 308232 , Singapore
| | | | - Sanjay H Chotirmall
- Lee Kong Chian School of Medicine , Nanyang Technological University , 11 Mandalay Road , 308232 , Singapore
| | | | - Michael Riediker
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
- IOM Singapore , 237 Alexandra Road , 159929 , Singapore
| | - David C Christiani
- Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health , Harvard University , 665 Huntington Avenue , Boston , Massachusetts 02115 , United States
| | - Mingliang Fang
- School of Civil and Environmental Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
| | - Dhimiter Bello
- Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health , Harvard University , 665 Huntington Avenue , Boston , Massachusetts 02115 , United States
| | - Philip Demokritou
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
- Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health , Harvard University , 665 Huntington Avenue , Boston , Massachusetts 02115 , United States
| | - Kee Woei Ng
- School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore
- Center for Nanotechnology and Nanotoxicology, Harvard T.H. Chan School of Public Health , Harvard University , 665 Huntington Avenue , Boston , Massachusetts 02115 , United States
- Skin Research Institute of Singapore , Biomedical Science Institutes , Immunos, 8A Biomedical Grove , 138648 , Singapore
- Environmental Chemistry & Materials Centre, Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University , 1 Cleantech Loop, CleanTech One , 637141 , Singapore
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