Co-reporter:Bingcheng Yi, Huilan Zhang, Zhepao Yu, Huihua Yuan, Xiangxin Lou, Yanzhong Zhang
Journal of Controlled Release 2017 Volume 259(Volume 259) pp:
Publication Date(Web):10 August 2017
DOI:10.1016/j.jconrel.2017.03.055
Co-reporter:Min Bao, Xianliu Wang, Huihua Yuan, Xiangxin Lou, Qinghua Zhao and Yanzhong Zhang
Journal of Materials Chemistry A 2016 vol. 4(Issue 31) pp:5308-5320
Publication Date(Web):15 Jul 2016
DOI:10.1039/C6TB01305H
In the clinical setting of bone fracture healing, hardware removal often causes localized microtrauma and residual screw holes may act as stress risers to place the patient at a risk of refracture. To address this noted issue, this study proposed to develop a biologically mimicking and mechanically self-actuated nanofibrous screw-like scaffold/implant for potential in situ bone regeneration. By incorporating nano-hydroxyapatite (HAp) into a shape memory copolymer poly(D,L-lactide-co-trimethylene carbonate) (PLMC) via co-electrospinning, composite nanofibers of HAp/PLMC with various HAp proportions (1, 2 and 3 wt%) were successfully generated. Morphological, thermal and mechanical properties as well as the shape memory effect of the resultant HAp/PLMC nanofibers were characterized using a variety of techniques. Thereafter, osteoblasts isolated from rat calvarial were cultured on the fibrous HAp/PLMC scaffold to assess its suitability for bone regeneration in vitro. We found that agglomerates gradually appeared on the fiber surface with increasing HAp loading fraction. The switching temperature for actuating shape recovery Ts (i.e., glass transition temperature Tg) of the fibrous HAp/PLMC was readily modulated to fall between 43.5 and 51.3 °C by varying the HAp loadings. Excellent shape memory properties were achieved for the HAp/PLMC composite nanofibers with a shape recovery ratio of Rr > 99% and shape fixity ratio of Rf > 99%, and the shape recovery force of the HAp/PLMC nanofibers was also strengthened compared to that of the HAp-free PLMC nanofibers. Moreover, we demonstrated that the engineered screw-like HAp/PLMC scaffold/implant (ϕ = 5 mm) was able to return from a slender bar to its original stumpy shape in a time frame of merely 8 s at 48 °C. Biological assay results corroborated that the incorporation of HAp to PLMC nanofibers significantly enhanced the alkaline phosphatase secretion as well as mineral deposition in bone formation. These attractive results warrant further investigation in vivo on the feasibility of applying the biomimicking nanofibrous HAp/PLMC scaffold with shape memory effect for bone screw hole healing.
Co-reporter:Jing Xie, Chen Peng, Qinghua Zhao, Xianliu Wang, Huihua Yuan, Liangliang Yang, Kai Li, Xiangxin Lou, Yanzhong Zhang
Acta Biomaterialia 2016 Volume 29() pp:365-379
Publication Date(Web):1 January 2016
DOI:10.1016/j.actbio.2015.10.007
Abstract
Induced pluripotent stem cell-derived mesenchymal stem cells (iPSC-MSCs) are a new type of MSCs that come with attractive merits over the iPSCs per se. Aimed for regenerating bone tissues, this study was designed to investigate osteogenic differentiation and bone regeneration capacities of iPSC-MSCs by using biomimetic nanofibers of hydroxyapatite/collagen/chitosan (HAp/Col/CTS). Murine iPSCs were firstly induced to differentiate into iPSC-MSCs and thoroughly characterized. Effects of HAp/Col/CTS nanofibers prepared from electrospinning of Col-doped HAp/CTS nanocomposite, on osteogenic differentiation of the generated iPSC-MSCs were then evaluated in detail, including cell morphology, proliferation, migration, quantified specific osteogenic gene and protein expressions. Compared with different controls (TCP, CTS, and HAp/CTS), the HAp/Col/CTS scaffold was found to have more favorable effects on attachment and proliferation of iPSC-MSCs than others (P < 0.01). Expressions of osteogenic genes, Runx2, Ocn, Alp, and Col, were significantly upregulated in iPSC-MSCs cultured on HAp/Col/CTS than CTS (P < 0.01). Similarly, there appeared considerably higher secreting activities of osteogenesis protein markers, ALP and Col. Furthermore, mouse cranial defects were created to investigate efficacy of using iPSC-MSCs in combination with HAp/Col/CTS scaffold for regenerative bone repair in vivo. Examinations by computed tomography (CT) imaging, bone mineral density and hematoxylin eosin (HE) staining corroborated that cell-scaffold construct of iPSC-MSCs + HAp/Col/CTS could effectively promote bone regeneration. After 6 weeks of implantation, bone mineral density of the iPSC-MSCs + HAp/Col/CTS group was found to be nearly 2-fold higher than others. Our results demonstrated that biomimetic nanofibers of HAp/Col/CTS promoted the osteogenic differentiation and bone regeneration of iPSC-MSCs. The iPSC-MSCs + HAp/Col/CTS complex could be used as a new ‘stem cell-scaffold’ system for realizing personalized and efficacious bone regeneration in future.
Statement of Significance
In bone tissue engineering, stem cells have become the most important source of seed cells. iPSC-MSCs are a new type of MSCs that come with attractive merits over the iPSCs per se. However, how to obtain befitting iPSC-MSCs and regulate their osteogenic differentiation are the key issues to be addressed. Given the great biomimicking capacity to extracellular matrix, electrospun nanofibers may be explored to modulate osteogenic differentiation of the iPSC-MSCs.
This study successfully demonstrated that biomimetic nanofibers of HAp/Col/CTS significantly promoted the osteogenic differentiation and bone regeneration of iPSC-MSCs, which thereby suggests that nanofibrous scaffold supported iPSC-MSCs complex may be a new ‘stem cell-scaffold’ system for regulating the fate of osteogenic differentiation of iPSC-MSCs towards patient-specific bone regeneration in future.
Co-reporter:Huihua Yuan, Yaxian Zhou, Ming-Song Lee, Yanzhong Zhang, Wan-Ju Li
Acta Biomaterialia 2016 Volume 42() pp:247-257
Publication Date(Web):15 September 2016
DOI:10.1016/j.actbio.2016.06.034
Abstract
Stiffness of biomaterial substrates plays a critical role in regulation of cell behavior. Although the effect of substrate stiffness on cell behavior has been extensively studied, molecular mechanisms of regulation rather than those involving cytoskeletal activities still remain elusive. In this study, we fabricated aligned ultrafine fibers and treated the fiber with different annealing temperatures to produce fibrous substrates with different stiffness. Human mesenchymal stem cells (hMSCs) were then cultured on these fibrous substrates. Our results showed that annealing treatment did not change the diameter of electrospun fibers but increased their polymer crystallinity and mechanical properties. The mRNA expression of RUNX2 was upregulated while the mRNA expression of scleraxis was downregulated in response to an increase in substrate stiffness, suggesting that increased stiffness favorably drives hMSCs into the osteogenic lineage. With subsequent induction of osteogenic differentiation, osteogenesis of hMSCs on stiffer substrates was increased compared to that of the cells on control substrates. Cells on stiffer substrates increasingly activated AKT and YAP and upregulated transcript expression of YAP target genes compared to those on control substrates, and inhibition of AKT led to decreased expression of YAP and RUNX2. Furthermore, macrophage migration inhibitory factor (MIF) was increasingly produced by the cell on stiffer substrates, and knocking down MIF by siRNA resulted in decreased AKT phosphorylation. Taken together, we hereby demonstrate that simply using the annealing approach can manipulate stiffness of an aligned fibrous substrate without altering the material chemistry, and substrate stiffness dictates hMSC differentiation through the MIF-mediated AKT/YAP/RUNX2 pathway.
Statement of Significance
Stiffness of biomaterial substrates plays a critical role in regulation of cell behavior. Although the effect of substrate stiffness on cell behavior has been extensively studied, molecular mechanisms of regulation rather than those involving cytoskeletal activities still remain elusive. In this manuscript, we report our new findings that simply using the annealing approach can manipulate stiffness of an aligned fibrous substrate without altering the material chemistry, and substrate stiffness dictates human mesenchymal stem cell (hMSC) differentiation through the macrophage migration inhibitory factor-mediated AKT/YAP/RUNX2 pathway. The findings are novel and interesting because we have identified a new mechanism rather than those involving cytoskeleton activity, by which substrate stiffness regulates hMSC behavior.
Co-reporter:Qihui Zhou, Jing Xie, Min Bao, Huihua Yuan, Zhaoyang Ye, Xiangxin Lou and Yanzhong Zhang
Journal of Materials Chemistry A 2015 vol. 3(Issue 21) pp:4439-4450
Publication Date(Web):27 Apr 2015
DOI:10.1039/C5TB00051C
In tissue engineering research, aligned electrospun ultrafine fibers have been shown to regulate cellular alignment and relevant functional expression, but the imposed effect of individual fiber surface nanotopography on cell behaviour has not been examined closely. This work investigates the impact of superimposing a nano-pore feature atop individual fiber surfaces on the responsive behaviour of human vascular smooth muscle cells (vSMCs) for blood vessel tissue engineering. Well-aligned ultrafine poly(L-lactic acid) (PLLA) microfibers with an average fiber diameter of ca. 1.6 μm were fabricated by using a novel stable jet electrospinning (SJES) method. Ellipse-shaped nano-pores with varied aspect ratios (defined as long-to-short axis ratio) of 2.7–3.9, corresponding to a surface nano-roughness in the range of 54.8–110.0 nm, were in situ generated onto individual fiber surfaces by varying ambient humidity from 45% to 75% during the SJES process. The presence of elliptical nano-pores on fiber surfaces affected the characteristic anisotropic wettability of the aligned PLLA fibers and contributed to greater protein adsorption (up to 17.59 μg mg−1). A 7 day in vitro assessment of human umbilical arterial SMCs cultured on these aligned nano-porous fiber substrates indicated that cellular responses were in close correlation with the elliptical nano-pore feature. A pronounced fiber surface nanotopography was superior in soliciting favorable cellular responses, leading to enhanced cell attachment, proliferation, alignment, expression of the vascular matrix proteins and maintenance of a contractile phenotype. This study thus suggests that introduction of an elliptical nano-pore feature to the aligned microfiber surfaces could provide additional dimensionality of topographical cues to modulate the vSMC responses when using the aligned electrospun ultrafine fibers for engineering vascular constructs.
Co-reporter:Huihua Yuan, Kai Li, Biyun Li, Xiangxin Lou, Qinghua Zhao, Yanzhong Zhang
Journal of Controlled Release 2015 Volume 213() pp:e43-e44
Publication Date(Web):10 September 2015
DOI:10.1016/j.jconrel.2015.05.070
Co-reporter:Bei Feng;Huichuan Duan;Wei Fu;Yilin Cao;Wen Jie Zhang
Journal of Biomedical Materials Research Part A 2015 Volume 103( Issue 2) pp:431-438
Publication Date(Web):
DOI:10.1002/jbm.a.35184
Abstract
In this article, gelatin (GT) and polycaprolactone (PCL) blended with a weight ratio of 50:50 were dissolved in the trifluoroethanol (TFE) or the acetic acid-doped TFE solvent system (0.2% relative to TFE) to prepare fibrous scaffolds of GT/PCL with different compositional and morphological homogeneities (denoted as the group 1 and the group 2 scaffolds) by electrospinning. The morphology and composition of the two groups of fibrous scaffolds were examined by scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. Then, using green fluorescence protein-labeled mouse fibroblasts and HaCaT cells (a human keratinocyte cell line) as the model cells, cell adhesion, morphology, and proliferation were assessed by laser scanning confocal microscopy, scanning electron microscopy, and cell counting kit-8 assay, respectively. The results showed that the morphological and compositional inhomogeneity of the group 1 scaffolds had a remarkable influence on cell adhesion and proliferation. In contrast, there was no significant difference among the group 2 scaffolds because of their good consistency in fiber morphology and composition. Phase separation resultant GT content variance in the group 1 scaffolds is suggested as one of the major causes. This study highlighted the importance of producing morphologically uniform and compositionally homogeneous composite nanofibers while electrospinning natural and synthetic polymer blends. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 431–438, 2015.
Co-reporter:Can Zhang, Huihua Yuan, Huanhuan Liu, Xiao Chen, Ping Lu, Ting Zhu, Long Yang, Zi Yin, Boon Chin Heng, Yanzhong Zhang, Hongwei Ouyang
Biomaterials 2015 53() pp: 716-730
Publication Date(Web):
DOI:10.1016/j.biomaterials.2015.02.051
Co-reporter:Min Bao, Xiangxin Lou, Qihui Zhou, Wen Dong, Huihua Yuan, and Yanzhong Zhang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 4) pp:2611
Publication Date(Web):January 29, 2014
DOI:10.1021/am405101k
Multifunctional fibrous scaffolds, which combine the capabilities of biomimicry to the native tissue architecture and shape memory effect (SME), are highly promising for the realization of functional tissue-engineered products with minimally invasive surgical implantation possibility. In this study, fibrous scaffolds of biodegradable poly(d,l-lactide-co-trimethylene carbonate) (denoted as PDLLA-co-TMC, or PLMC) with shape memory properties were fabricated by electrospinning. Morphology, thermal and mechanical properties as well as SME of the resultant fibrous structure were characterized using different techniques. And rat calvarial osteoblasts were cultured on the fibrous PLMC scaffolds to assess their suitability for bone tissue engineering. It is found that by varying the monomer ratio of DLLA:TMC from 5:5 to 9:1, fineness of the resultant PLMC fibers was attenuated from ca. 1500 down to 680 nm. This also allowed for readily modulating the glass transition temperature Tg (i.e., the switching temperature for actuating shape recovery) of the fibrous PLMC to fall between 19.2 and 44.2 °C, a temperature range relevant for biomedical applications in the human body. The PLMC fibers exhibited excellent shape memory properties with shape recovery ratios of Rr > 94% and shape fixity ratios of Rf > 98%, and macroscopically demonstrated a fast shape recovery (∼10 s at 39 °C) in the pre-deformed configurations. Biological assay results corroborated that the fibrous PLMC scaffolds were cytocompatible by supporting osteoblast adhesion and proliferation, and functionally promoted biomineralization-relevant alkaline phosphatase expression and mineral deposition. We envision the wide applicability of using the SME-capable biomimetic scaffolds for achieving enhanced efficacy in repairing various bone defects (e.g., as implants for healing bone screw holes or as barrier membranes for guided bone regeneration).Keywords: biomineralization; bone tissue engineering; electrospun fibrous scaffold; osteoblasts; poly(d,l-lactide-co-trimethylene carbonate); Shape memory polymer;
Co-reporter:Shifang Zhao, Qihui Zhou, Yun-Ze Long, Guang-Hui Sun and Yanzhong Zhang
Nanoscale 2013 vol. 5(Issue 11) pp:4993-5000
Publication Date(Web):08 Apr 2013
DOI:10.1039/C3NR00676J
Patterning of electrospun nanofibers has recently attracted much attention for its usefulness in a wide range of applications. This paper reports on the generation of spatially defined nanofibrous patterns by direct deposition of electrospun nanofibers onto a variety of insulating substrates. It was found that topographical features of different non-conducting substrates could be readily replicated by the electrospun nanofibers of interest. To elucidate the underlying mechanism of nanofiber patterning, we have systematically studied the effects of surface topography of non-conducting substrates (in particular protrusions) on the nanofiber deposition and assembly. Results from experiments and electric field simulation indicated that under a strong electric field the insulating substrates can be polarized, which could consequently affect the distribution of the original electric field. For particular non-conductive substrates with small mesh sizes or sufficient thickness, surface topography of the dielectric substrate may play a key role in determining the deposition and the arrangement of electrospun fibers. In addition, parameters that could influence the fineness of nanofibrous patterns have also been investigated. This contribution is believed to warrant further scientific understanding of the patterning mechanism of electrospun nanofibers, and to allow for design of specific and complex non-conductive substrate collectors for easy generation of patterned nanofibrous architectures, applicable in a variety of areas such as tissue engineering scaffolds and optoelectronic displays.
Co-reporter:Jixin Xue, Bei Feng, Rui Zheng, Yang Lu, Guangdong Zhou, Wei Liu, Yilin Cao, Yanzhong Zhang, Wen Jie Zhang
Biomaterials 2013 34(11) pp: 2624-2631
Publication Date(Web):
DOI:10.1016/j.biomaterials.2012.12.011
Co-reporter:Huanhuan Liu, Hongju Peng, Yan Wu, Can Zhang, Youzhi Cai, Guowei Xu, Qin Li, Xiao Chen, Junfeng Ji, Yanzhong Zhang, Hong Wei OuYang
Biomaterials 2013 34(18) pp: 4404-4417
Publication Date(Web):
DOI:10.1016/j.biomaterials.2013.02.048
Co-reporter:Qihui Zhou, Min Bao, Huihua Yuan, Shifang Zhao, Wen Dong, Yanzhong Zhang
Polymer 2013 Volume 54(Issue 25) pp:6867-6876
Publication Date(Web):27 November 2013
DOI:10.1016/j.polymer.2013.10.042
Stable jet based electrospinning (SJES) has recently emerged as a straight-forward approach for the continuous fabrication of well-aligned ultrafine fibers and fiber assemblies. This article reports on the influences of some pivotal solution parameters including solvent, polymer molecular weight, and concentration on the formation of a stable jet length (SJL) in electrospinning of a biodegradable polymer, poly(l-lactide acid) (PLLA). Our results reveal that enhanced critical SJL can be achieved at lower solvent dielectric constant and higher viscoelasticity of solutions contributed by the molecular weight and concentration, beneficial for achieving higher degree of fiber alignment. Moreover, hierarchical orderliness including the macroscopic fiber alignment, the elongation along the fiber direction of microscopic pores on the fiber surface and the molecular orientation within the electrospun PLLA fibers, can be modulated by the SJL. The molecular orientation and crystallinity of the aligned PLLA fibers from SJES increased with increasing the SJLs. Also, the measured tensile properties data suggest a positive trend associated with the SJL. This study thus allows establishing a solid correlation of SJL with respect to the macroscopic alignment, internal molecular structural development, and mechanical performance of the electrospun ultrafine PLLA fibers pertaining to the SJES.
Co-reporter:Min Bao, Qihui Zhou, Wen Dong, Xiangxin Lou, and Yanzhong Zhang
Biomacromolecules 2013 Volume 14(Issue 6) pp:
Publication Date(Web):May 15, 2013
DOI:10.1021/bm4003464
Minimally invasive implants and/or scaffolds integrated with multiple functionalities are of interest in the clinical settings. In this paper, chitosan (CTS) functionalized poly(lactic-co-glycolic acid) (PLGA) microspheres containing a model payload, lysozyme (Lyz), were prepared by a water-in-oil-in-water emulsion method, from which cylindrical shaped rod (5 mm in diameter) was fabricated by sintering the composite microspheres in a mold. High-intensity focused ultrasound (HIFU) was then employed as a unique technique to enable shape memory and payload release effects of the three-dimensional (3-D) structure. It was found that incorporation of CTS into PLGA microspheres could regulate the transition temperature Ttrans of the microsphere from 45 to 50 °C and affect shape memory ratio of the fabricated cylindrical rod to some extent. Shape memory test and drug release assay proved that HIFU could modulate the shape recovery process and synchronize the release kinetics of the encapsulated Lyz in the rod in a switchable manner. Moreover, the two processes could be manipulated by varying the acoustic power and insonation duration. Mechanical tests of the microspheres-based rod before and after ultrasound irradiation revealed its compressive properties in the range of trabecular bone. Examination of the degradation behavior indicated that the introduction of CTS into the PLGA microspheres also alleviated acidic degradation characteristic of the PLGA-dominant cylindrical rod. With HIFU, this study thus demonstrated the desired capabilities of shape recovery and payload release effects integrated in one microspheres-based biodegradable cylindrical structure.
Co-reporter:Huihua Yuan, Shifang Zhao, Hongbin Tu, Biyun Li, Qin Li, Bei Feng, Hongju Peng and Yanzhong Zhang
Journal of Materials Chemistry A 2012 vol. 22(Issue 37) pp:19634-19638
Publication Date(Web):06 Aug 2012
DOI:10.1039/C2JM33728B
Electrospinning has emerged as an attractive technique for the fabrication of ultrafine fibers in micro-/nano-scale fineness. However, it is still a huge technological challenge in achieving aligned fibers and arrays due to the inherent chaotic motion of an electrospinning jet. We report herein a novel spinning approach termed stable jet electrospinning to offer a facile solution to the noted issue. It involves judiciously using an ultrahigh molecular weight poly(ethylene oxide) to formulate the viscoelasticity of a spinning dope such that a very long and stable jet can be formed during electrospinning. This consequently allows for readily collecting and fabricating individual fibers, multi-filament yarns, well-aligned unidirectional fiber arrays in a large area, and ordered fiber patterns by controlling fiber placement. Our approach could thus open up the possibility of achieving continuous aligned ultrafine fibers and structures in a straightforward and scalable fashion, suitable for a variety of practical applications.
Co-reporter:Bei Feng, Hongbin Tu, Huihua Yuan, Hongju Peng, and Yanzhong Zhang
Biomacromolecules 2012 Volume 13(Issue 12) pp:
Publication Date(Web):November 6, 2012
DOI:10.1021/bm3009389
In tissue engineering research, there has recently been considerable interest in using electrospun biomimetic nanofibers of hybrids, in particular, from natural and synthetic polymers for engineering different tissues. However, phase separation between a pair of much dissimilar polymers might give rise to detrimental influences on both the electrospinning process and the resultant fiber performance. A representative natural-synthetic hybrid of gelatin (GT) and polycaprolactone (PCL) (50:50) was employed to study the phase separation behavior in electrospinning of the GT/PCL composite fibers. Using trifluoroethanol (TFE) as the cosolvent of the two polymers, observation of visible sedimentation and flocculation from dynamic light scattering analysis of the GT/PCL/TFE mixture both showed that phase separation does occur in just a few hours. This consequently led to gradually deteriorated fiber morphologies (e.g., splash, fiber bonding, and varied fiber size) over time during electrospinning GT/PCL. Quantitative analysis also indicated that the ratio of GT to PCL in the resultant GT/PCL fibers was altered over time. To address the phase separation related issues, a tiny amount (<0.3%) of acetic acid was introduced to improve the miscibility, which enabled the originally turbid solution to become clear immediately and to be single-phase stable for more than 1 week. Nanofibers thus obtained also appeared to be thinner, smooth, and homogeneous with enhanced performance in wettability and mechanical properties. Given the versatility and widely uses of the electrospun GT/PCL and other similar natural-synthetic hybrid systems in constructing tissue-engineered scaffolds, this work may offer a facile and effective approach to achieve finer and compositionally homogeneous hybrid nanofibers for effective applications.
Co-reporter:Huihui Liao, Ruiling Qi, Mingwu Shen, Xueyan Cao, Rui Guo, Yanzhong Zhang, Xiangyang Shi
Colloids and Surfaces B: Biointerfaces 2011 Volume 84(Issue 2) pp:528-535
Publication Date(Web):1 June 2011
DOI:10.1016/j.colsurfb.2011.02.010
We report the fabrication of multiwalled carbon nanotube (MWCNT)-incorporated electrospun polyvinyl alcohol (PVA)/chitosan (CS) nanofibers with improved cellular response for potential tissue engineering applications. In this study, smooth and uniform PVA/CS and PVA/CS/MWCNTs nanofibers with water stability were formed by electrospinning, followed by crosslinking with glutaraldehyde vapor. The morphology, structure, and mechanical properties of the formed electrospun fibrous mats were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and mechanical testing, respectively. We showed that the incorporation of MWCNTs did not appreciably affect the morphology of the PVA/CS nanofibers; importantly the protein adsorption ability of the nanofibers was significantly improved. In vitro cell culture of mouse fibroblasts (L929) seeded onto the electrospun scaffolds showed that the incorporation of MWCNTs into the PVA/CS nanofibers significantly promoted cell proliferation. Results from this study hence suggest that MWCNT-incorporated PVA/CS nanofibrous scaffolds with small diameters (around 160 nm) and high porosity can mimic the natural extracellular matrix well, and potentially provide many possibilities for applications in the fields of tissue engineering and regenerative medicine.Graphical abstractResearch highlights► The incorporation of MWCNTs did not appreciably affect the morphology of the PVA/CS nanofibers. ► Protein adsorption on the nanofibers was greatly improved upon the incorporation of MWCNTs. ► The incorporation of MWCNTs into the PVA/CS nanofibers significantly promoted cell proliferation. ► MWCNT-incorporated PVA/CS nanofibers may be used for applications in tissue engineering.
Co-reporter:Charles L. Parsons
Science 1921 Vol 53(1367) pp:239-242
Publication Date(Web):11 Mar 1921
DOI:10.1126/science.53.1367.239
Co-reporter:Huihua Yuan, Shifang Zhao, Hongbin Tu, Biyun Li, Qin Li, Bei Feng, Hongju Peng and Yanzhong Zhang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 37) pp:NaN19638-19638
Publication Date(Web):2012/08/06
DOI:10.1039/C2JM33728B
Electrospinning has emerged as an attractive technique for the fabrication of ultrafine fibers in micro-/nano-scale fineness. However, it is still a huge technological challenge in achieving aligned fibers and arrays due to the inherent chaotic motion of an electrospinning jet. We report herein a novel spinning approach termed stable jet electrospinning to offer a facile solution to the noted issue. It involves judiciously using an ultrahigh molecular weight poly(ethylene oxide) to formulate the viscoelasticity of a spinning dope such that a very long and stable jet can be formed during electrospinning. This consequently allows for readily collecting and fabricating individual fibers, multi-filament yarns, well-aligned unidirectional fiber arrays in a large area, and ordered fiber patterns by controlling fiber placement. Our approach could thus open up the possibility of achieving continuous aligned ultrafine fibers and structures in a straightforward and scalable fashion, suitable for a variety of practical applications.
Co-reporter:Min Bao, Xianliu Wang, Huihua Yuan, Xiangxin Lou, Qinghua Zhao and Yanzhong Zhang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 31) pp:NaN5320-5320
Publication Date(Web):2016/07/15
DOI:10.1039/C6TB01305H
In the clinical setting of bone fracture healing, hardware removal often causes localized microtrauma and residual screw holes may act as stress risers to place the patient at a risk of refracture. To address this noted issue, this study proposed to develop a biologically mimicking and mechanically self-actuated nanofibrous screw-like scaffold/implant for potential in situ bone regeneration. By incorporating nano-hydroxyapatite (HAp) into a shape memory copolymer poly(D,L-lactide-co-trimethylene carbonate) (PLMC) via co-electrospinning, composite nanofibers of HAp/PLMC with various HAp proportions (1, 2 and 3 wt%) were successfully generated. Morphological, thermal and mechanical properties as well as the shape memory effect of the resultant HAp/PLMC nanofibers were characterized using a variety of techniques. Thereafter, osteoblasts isolated from rat calvarial were cultured on the fibrous HAp/PLMC scaffold to assess its suitability for bone regeneration in vitro. We found that agglomerates gradually appeared on the fiber surface with increasing HAp loading fraction. The switching temperature for actuating shape recovery Ts (i.e., glass transition temperature Tg) of the fibrous HAp/PLMC was readily modulated to fall between 43.5 and 51.3 °C by varying the HAp loadings. Excellent shape memory properties were achieved for the HAp/PLMC composite nanofibers with a shape recovery ratio of Rr > 99% and shape fixity ratio of Rf > 99%, and the shape recovery force of the HAp/PLMC nanofibers was also strengthened compared to that of the HAp-free PLMC nanofibers. Moreover, we demonstrated that the engineered screw-like HAp/PLMC scaffold/implant (ϕ = 5 mm) was able to return from a slender bar to its original stumpy shape in a time frame of merely 8 s at 48 °C. Biological assay results corroborated that the incorporation of HAp to PLMC nanofibers significantly enhanced the alkaline phosphatase secretion as well as mineral deposition in bone formation. These attractive results warrant further investigation in vivo on the feasibility of applying the biomimicking nanofibrous HAp/PLMC scaffold with shape memory effect for bone screw hole healing.
Co-reporter:Qihui Zhou, Jing Xie, Min Bao, Huihua Yuan, Zhaoyang Ye, Xiangxin Lou and Yanzhong Zhang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 21) pp:NaN4450-4450
Publication Date(Web):2015/04/27
DOI:10.1039/C5TB00051C
In tissue engineering research, aligned electrospun ultrafine fibers have been shown to regulate cellular alignment and relevant functional expression, but the imposed effect of individual fiber surface nanotopography on cell behaviour has not been examined closely. This work investigates the impact of superimposing a nano-pore feature atop individual fiber surfaces on the responsive behaviour of human vascular smooth muscle cells (vSMCs) for blood vessel tissue engineering. Well-aligned ultrafine poly(L-lactic acid) (PLLA) microfibers with an average fiber diameter of ca. 1.6 μm were fabricated by using a novel stable jet electrospinning (SJES) method. Ellipse-shaped nano-pores with varied aspect ratios (defined as long-to-short axis ratio) of 2.7–3.9, corresponding to a surface nano-roughness in the range of 54.8–110.0 nm, were in situ generated onto individual fiber surfaces by varying ambient humidity from 45% to 75% during the SJES process. The presence of elliptical nano-pores on fiber surfaces affected the characteristic anisotropic wettability of the aligned PLLA fibers and contributed to greater protein adsorption (up to 17.59 μg mg−1). A 7 day in vitro assessment of human umbilical arterial SMCs cultured on these aligned nano-porous fiber substrates indicated that cellular responses were in close correlation with the elliptical nano-pore feature. A pronounced fiber surface nanotopography was superior in soliciting favorable cellular responses, leading to enhanced cell attachment, proliferation, alignment, expression of the vascular matrix proteins and maintenance of a contractile phenotype. This study thus suggests that introduction of an elliptical nano-pore feature to the aligned microfiber surfaces could provide additional dimensionality of topographical cues to modulate the vSMC responses when using the aligned electrospun ultrafine fibers for engineering vascular constructs.
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