Wafer-Scale Multilayer Fabrication for Silk Fibroin-Based Microelectronics

Kook, Geon,Jeong, Sohyeon,Kim, So Hyun,Kim, Mi Kyung,Lee, Sungwoo,Cho, Il-Joo,Choi, Nakwon,Lee, Hyunjoo J. American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.1

<P>Silk fibroin is an excellent candidate for biomedical implantable devices because of its biocompatibility, controllable biodegradability, solution processability, flexibility, and transparency. Thus, fibroin has been widely explored in biomedical applications as biodegradable films as well as functional microstructures. Although there exists a large number of patterning methods for fibroin thin films, multilayer micropatterning of fibroin films interleaved with metal layers still remains a challenge. Herein, we report a new wafer-scale multilayer microfabrication process named aluminum hard mask on silk fibroin (AMoS), which is capable of micropatterning multiple layers composed of both fibroin and inorganic materials (e.g., metal and dielectrics) with high-precision microscale alignment. To the best of our knowledge, our AMoS process is the first demonstration of wafer-scale multilayer processing of both silk fibroin and metal micropatterns. In the AMoS process, aluminum deposited on fibroin is first micropatterned using conventional ultraviolet (UV) photolithography, and the patterned aluminum layer is then used as a mask to pattern fibroin underneath. We demonstrate the versatility of our fabrication process by fabricating fibroin microstructures with different dimensions, passive electronic components composed of both fibroin and metal layers, and functional fibroin microstructures for drug delivery. Furthermore, because one of the crucial advantages of fibroin is biocompatibility, we assess the biocompatibility of our fabrication process through the culture of highly susceptible primary neurons. Because the AMoS process utilizes conventional UV photolithography, the principal advantages of our process are multilayer fabrication with high-precision alignment, high resolution, wafer-scale large area processing, no requirement for chemical modification of the protein, and high throughput and thus low cost, all of which have not been feasible with silk fibroin. Therefore, the proposed fabrication method is a promising candidate for batch fabrication of functional fibroin microelectronics (e.g., memristors and organic thin film transistors) for next-generation implantable biomedical applications.</P> [FIG OMISSION]</BR>

Synthesis of hollow fibroin using calcium carbonate as a template

박병호,Ramesh Siva Kumar,이석우,김진권 대한화학회 2023 Bulletin of the Korean Chemical Society Vol.44 No.3

Silk fibroin is a unique biomaterial and has gained much attention in biomedi- cal applications. In this study, we have demonstrated the formation of hollow fibroin using the selective etching method. Initially, spherical CaCO3 was syn- thesized in the presence of polyelectrolyte, poly(4-styrenesulfonate). CaCO3 particles were treated with aqueous silk fibroin solution, followed by methanol treatment. The sequential deposition of silk fibroin was achieved through a layer-by-layer (LbL) strategy to obtain fibroin-encapsulated CaCO3. Finally, the fibroin- encapsulated CaCO3 was treated with an acid solution to form hollow fibroin. The crystalline phase of as-prepared products was measured using powder X-ray diffraction, and vibrational modes of products were characterized using Fourier transform infrared spectroscopy. The hollow fibroin morphology was examined using electron microscopy. The resultant hollow fibroin has good stability and can be explored in various applications.

Mechanical Properties of Hydrated Silk Fibroin/Bacterial Cellulose Composite Films

정리라,김예슬,진형준,Jung, Ri-Ra,Kim, Ye-Seul,Jin, Hyoung-Joon The Korean Fiber Society 2007 한국섬유공학회지 Vol.44 No.3

Composite films consisting of two biocompatible natural polymers were prepared by incorporating bacterial cellulose into silk fibroin. The high crystalline cellulose hydrogel was synthesized by bacteria, Acetobacter xylinum. Silk fibroin was finely blended with the bacterial cellulose fibrils by adding aqueous silk fibroin solution into the bacterial cellulose hydrogel. We observed individual bacterial cellulose fibrils within a silk fibroin matrix by field emission scanning electron microscopy. The silk fibroin well penetrated between the individual fibrils of the bacterial cellulose. The silk fibroin/bacterial cellulose composite film did not dissolve in water without further crystallization process, whereas a pure silk fibroin film easily dissolved in water without crystallization process. The crystallization phenomenon of silk fibroin in the composite film was verified by X-ray diffraction and Fourier transform-infrared spectroscopy. Furthermore, the mechanical properties of the silk fibroin/bacterial cellulose composite film markedly increased when the composite film was hydrated. The silk fibroin/bacterial cellulose composite films became more flexible and tougher when they were hydrated, while it was very brittle in the dehydrated state.

키토산과 견사 단백질 복합체의 특성

김희숙,원용돈,류병호 한국식품영양학회 1996 韓國食品營養學會誌 Vol.9 No.4

기능성 다이어트 식품을 개발을 목적으로, 키토산과 견 피브로인의 복합체를 만들고 성질을 조사하였다. 키토산은 대동새우로부터 추출하였고, 견사 피브로인 섬유는 누에로부터 추출하였다. 견사의 특성을 알아보기 위하여 용해도를 조사한 결과, 용해도는 8M LiBr이상의 농도와 40℃ 이상에서 가장 높았다. 견사 피브로인의 아미노산 조성은 천연견사 및 용해시킨 피브로인과 같았다. 키토산, 견사 피브로인 복합체의 아미노산 조성은 glycine, alanine, serine, tyrosine, threonine 및 glutamic acid 순서를 많았다. 또한 IR 스펙트럼 결과, 키토산·견사 피브로인 복합체는 배합비율에 따른 스텍트럼상의 차이는 거의 없었다. In order to develop the functional diet food, characteristics of chitosan and silk fibroin composite was designed. Chitosan extracted from a prawn and silk fibroin was prepared from silkworm. The silk fibroin was dissolved rapidly in the 8M LiBr at a temperatrue of more than 40℃. Amino acid composition of fibroin composite revealed the same pattern that of native silk fibroin and regenerated silk fibroin. Predominant amino acid of chitosan-fibroin composite contained glycine, alanine, serine, tyrosine, threonine, and glutamic acid in order. According to the basis on the infrared spectrum, chitosan-silk fibroin composite is not distinguished differents composite ratio of chitosan and silk fibroin.

다양한 구조를 가진 알긴산-피브로인 비드 제조

이진실(Jin Sil Lee),이신영(Shin-Young Lee),허원(Won Hur) 한국생물공학회 2011 KSBB Journal Vol.26 No.5

Alginate bead has been supplemented with various polymers to control permeability and to enhance mechanical strength. In this report, fibroin-reinforced alginate hydrogel was prepared, in which spatial localization of fibroin molecules was investigated. Confocal laser scanning microscopy revealed that fibroin molecules formed a fibrous network in the alginate-fibroin beads, which was expected to enhance mechanical strength as same as in many composite materials. Uniaxial compression test showed that fibroin-reinforced alginate beads had increased mechanical strength only after methanol treatment that caused β-sheet formation among fibroin molecules. Simultaneous curing and dialysis of alginate beads were carried out to remove excesscalcium but to retain fibroin in the dialysis chamber, which fabricated beads without internal fibrous fluorescent stains. Fibroin molecules were only found beneath the surface of the beads. The fibroin-diffused shell was further processed to form a thick wall after drying or was mobilizedto the centre of the bead by methanol treatment. Accordingly, the structure analyses provide processing methods of fibroin to form a wall or center clumps, which could be applied to design controlled delivery device.

반고형 피브로인 단백질 겔의 제조 및 유동특성

허원(Won Hur),이신영(Shin-Young Lee) 한국생물공학회 2009 KSBB Journal Vol.24 No.6

피브로인은 누에고치가 생산되는 불용성 단백질이다. 고온의 염화칼슘용액에서 가용화시킨 후 탈염하여 물에 녹게 만들 수 있다. 그러나 수용액은 불안정하여 피브로인 분자는 랜덤코일에서 β병풍구조의 비율이 증가하는 구조로 전이되고 겔을 형성한다. 그러나 피브로인 겔은 약하고 탄성이 없어 소재로 응용하는데 어려움이 있다. 본 연구에서는 글리세롤과 에탄올을 사용하여 반고형의 피브로인 겔을 제조하고 이들의 유동 특성을 조사하였다. 80%의 글리세롤로 만들어진 피브로인 겔은 의가소성 및 thixotropic 특성을 나타내었으며 항복응력의 제곱근 값이 피브로인의 농도와 선형적으로 비례하였으며 항복응력이 없어지는 피브로인의 농도는 0.2%로 확인되었다. 40% 에탄올에서 만들어진 피브로인 겔은 매우 심한 thixotropic 특성을 보였으며 전단속도가 어떤 값 이상이 되면 급격한 전단연화 현상을 나타내었다. 이 피브로인 겔은 전단이력 후 의가소성을 회복하는 특성을 나타내었다. Fibroin is an insoluble structural protein from Bombyx mori. It can be solubilized by dissolving in a hot CaCl2 solution and subsequent dialysis. The aqueous solution is unstable and a transition from aqueous fibroin molecules rich in random coil is undergo to one rich in β-sheet content, resulting in hydrogelation. However, fibroin gel is so fragile and plastic that its mechanical property should be reformed for various applications. In this report, a semi-solid form of fibroin gel was prepared using glycerol and ethanol and was investigated to analyze their flow properties. A fibroin gel with 80% glycerol showed pseudoplastic and thixotropic properties. The square root of its yield stress varied linearly with fibroin concentration and it extrapolated to zero shear stress at 0.2% fibroin. A fibroin gel with 40% ethanol was shown to be highly thixotropic but its shear-thinning behavior was only observed above a certain level of shear rate. Its pseudoplasticity was restored by a high rate of shear stress.

W/O 에멀젼에서 피브로인 분자의 회합 및 응집에 의한 미세구의 형성

이진실(Jin Sil Lee),김지영(Ji Young Kim),허원(Won Hur) 한국고분자학회 2016 폴리머 Vol.40 No.6

실크섬유의 구성단백질인 피브로인은 물에 녹지 않으나 고온의 염용액에 녹는다. 염용액을 투석하면 피브로인 수용액이 얻어지고, 시간이 경과하면 젤이 형성된다. 본 연구에서는 젤 형성 중간단계에 존재하는 피브로인 분자회합체를 광산란법으로 분석하였고, 시간의 경과에 따라 그 크기가 증가하는 것을 확인하였다. 피브로인 수용액에 데칸과 계면활성제를 섞어 유상수적(W/O)형의 에멀젼을 만들고 감압 건조시켜 미세구를 제조하였다. 피브로인 미세구는 매끄러운 표면의 구형을 유지하고 있으며, 수용액이나 식염수에 보관해도 불용성 상태를 유지하였다. 미세구의 불용성과 형태 안정성에 기여하는 피브로인 분자사슬의 β-sheet 구조와 결정성 영역을 적외선 분광 스펙트럼과 X선 회절 분석을 이용하여 확인하였다. Fibroin is an insoluble protein polymer of silk fiber but undergo solubilization in a hot salt solution. The fibroin-salt solution was dialyzed to obtain an unstable aqueous fibroin, eventually turned to gel. Molecular association of aqueous fibroin and their growth were detected by dynamic light scattering. Fibroin microspheres were prepared by dehydration of W/O emulsion from aqueous fibroin, mixed with decane and detergents. Scanning electron microscopy showed that fibroin microspheres have the smooth surface. The fibroin microspheres remain insoluble in water as well as in saline without any significant swelling. FTIR and XRD were used to detect the presence of β-sheet structure formed by hydrogen bonds between fibroin molecules in an orderly manner.

혼합 실크 피브로인막의 투명도

조유영 ( You Young Jo ),권해용 ( Hae Yong Kweon ),여주홍 ( Joo Hong Yeo ),이광길 ( Kwang Gill Lee ) 한국잠사학회 2013 한국잠사곤충학회지 Vol.51 No.2

Silk fibroin is a natural biomaterial that has the biocompatibility and other many advantages. But as a silk fibroin membrane thickness increases, the transparency becomes more opaque. Because the transparency of membranes tissue such as the cornea and dura mater are necessary, transparent membrane is required to replace these transparent membranes. In this study, we fabricated blending silk fibroin membranes that made by mixing the various inorganic salts or polymer in an aqueous solution of silk fibroin. The transparency of the membranes were analyzed. the transparency of these membranes is very different, depending on the mixed materials. Inorganic salts mixed silk membrane was more transparent than the polymer mixed one. Especially, the silk fibroin membrane with calcium chloride was very transparent. We showed the possibility of blending silk fibroin membrane, which can be used in perfect transparent membrane such as the cornea. In the future, we expect that the transparent blending silk fibroin membrane can be used in various medical applications.

Silk fibroin/collagen protein hybrid cell-encapsulating hydrogels with tunable gelation and improved physical and biological properties

Buitrago, Jennifer O.,Patel, Kapil D.,El-Fiqi, Ahmed,Lee, Jung-Hwan,Kundu, Banani,Lee, Hae-Hyoung,Kim, Hae-Won Elsevier 2018 ACTA BIOMATERIALIA Vol.69 No.-

<P><B>Abstract</B></P> <P>Cell encapsulating hydrogels with tunable mechanical and biological properties are of special importance for cell delivery and tissue engineering. Silk fibroin and collagen, two typical important biological proteins, are considered potential as cell culture hydrogels. However, both have been used individually, with limited properties (<I>e.g.,</I> collagen has poor mechanical properties and cell-mediated shrinkage, and silk fibroin from <I>Bombyx mori (mulberry)</I> lacks cell adhesion motifs). Therefore, the combination of them is considered to achieve improved mechanical and biological properties with respect to individual hydrogels. Here, we show that the cell-encapsulating hydrogels of mulberry silk fibroin / collagen are implementable over a wide range of compositions, enabled simply by combining the different gelation mechanisms. Not only the gelation reaction but also the structural characteristics, consequently, the mechanical properties and cellular behaviors are accelerated significantly by the silk fibroin / collagen hybrid hydrogel approach. Of note, the mechanical and biological properties are tunable to represent the combined merits of individual proteins. The shear storage modulus is tailored to range from 0.1 to 20 kPa along the iso-compositional line, which is considered to cover the matrix stiffness of soft-to-hard tissues. In particular, the silk fibroin / collagen hydrogels are highly elastic, exhibiting excellent resistance to permanent deformation under different modes of stress; without being collapsed or water-squeezed out (<I>vs.</I> not possible in individual proteins) – which results from the mechanical synergism of interpenetrating networks of both proteins. Furthermore, the role of collagen protein component in the hybrid hydrogels provides adhesive sites to cells, stimulating anchorage and spreading significantly with respect to mulberry silk fibroin gel, which lacks cell adhesion motifs. The silk fibroin / collagen hydrogels can encapsulate cells while preserving the viability and growth over a long 3D culture period. Our findings demonstrate that the silk / collagen hydrogels possess physical and biological properties tunable and significantly improved (<I>vs.</I> the individual protein gels), implying their potential uses for cell delivery and tissue engineering.</P> <P><B>Statement of Significance</B></P> <P>Development of cell encapsulating hydrogels with excellent physical and biological properties is important for the cell delivery and cell-based tissue engineering. Here we communicate for the first time the novel protein composite hydrogels comprised of ‘Silk’ and ‘Collagen’ and report their outstanding physical, mechanical and biological properties that are not readily achievable with individual protein hydrogels. The properties include i) gelation accelerated over a wide range of compositions, ii) stiffness levels covering 0.1 kPa to 20 kPa that mimic those of soft-to-hard tissues, iii) excellent elastic behaviors under various stress modes (bending, twisting, stretching, and compression), iv) high resistance to cell-mediated gel contraction, v) rapid anchorage and spreading of cells, and vi) cell encapsulation ability with a long-term survivability. These results come from the synergism of individual proteins of alpha-helix and beta-sheet structured networks. We consider the current elastic cell-encapsulating hydrogels of silk-collagen can be potentially useful for the cell delivery and tissue engineering in a wide spectrum of soft-to-hard tissues.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Monitoring of phase separation between silk fibroin and sericin using various dye system

( Hyo Won Kwak ),( Ki Hoon Lee ) 한국잠사학회 2015 International Journal of Industrial Entomology Vol.30 No.1

Understanding the interactions between fibroin and sericin is crucial in solving the mechanism of silk spinning. In this study, various commercially available dyes were used to monitor the interface between fibroin and sericin during the gelation of fibroin. The phase separation between fibroin and sericin could be observed by the addition of azo dyes over a certain molecular weight. Furthermore, the addition of the dyes to the sericin layer showed vivid phase separation over addition to the fibroin layer.