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ano Today (2011) 6, 232—239

avai lab le at www.sc iencedi rec t .com

journa l homepage: www.e lsev ier .com/ locate /nanotoday

APID COMMUNICATION

ltrasmall natural peptides self-assemble to strongemperature-resistant helical fibers in scaffoldsuitable for tissue engineering

rchana Mishraa,1, Yihua Looa,1, Rensheng Denga,1, Yon Jin Chuahb,wan Tak Heeb, Jackie Y. Yinga, Charlotte A.E. Hausera,∗

Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, Singapore 138669, SingaporeDepartment of Orthopedic Surgery, National University of Singapore, Yong Loo Lin School of Medicine, 1E Kent Ridge Road,ingapore 119228, Singapore

eceived 24 December 2010; received in revised form 12 April 2011; accepted 4 May 2011vailable online 2 June 2011

KEYWORDSUltrasmall peptides;Self-assembly;Hydrogels;Tissue engineering

Summary A new class of systematically designed ultrasmall (tri- to heptamer) peptidespresents the smallest natural, non-aromatic structures that self-assemble in water to hydrogels.The peptide motif consists of an aliphatic amino acid tail of decreasing hydrophobicity cappedby a polar head. The fibrous scaffolds assemble from nanostructured aggregates to condensedthree-dimensional (3D) meshes, entrapping up to 99.9% water and resembling collagen fibers

in the extracellular matrix. The resulting hydrogels are biocompatible, heat resistant up to90 ◦C and demonstrate tunable, high mechanical strength. Given their facile and cost-effectivesynthesis, these new materials would be attractive for applications ranging from injectablemedical therapies to tissue-engineered scaffolds.© 2011 Elsevier Ltd. All rights reserved.

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elf-assembled peptide aggregates are structures that cane applied as soft biomaterials [1—3]. Knowledge of theules of intermolecular association, the so-called bottom-uppproach, facilitates the design of molecular assembliesuch as membranes, films, layers, micelles, tubules and

els for a variety of biomedical or technological applica-ions [4,5]. When peptides self-assemble to hydrogels, 3Dcaffolds that entrap large amounts of water are formed.

∗ Corresponding author. Tel.: +65 6824 7108; fax: +65 6478 9080.E-mail address: chauser@ibn.a-star.edu.sg (C.A.E. Hauser).

1 These authors contributed equally to this work.

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748-0132/$ — see front matter © 2011 Elsevier Ltd. All rights reserved.oi:10.1016/j.nantod.2011.05.001

eptide-derived hydrogels are proposed as biomaterialsor tissue engineering, regenerative medicine, drug deliv-ry vehicles, peptide chips for pharmaceutical research,iagnosis [6], and molecular electronic devices [7]. Theseydrogels contain macroscopic structures such as fibershat entangle and form meshes. Peptide-derived hydrogelsssembled from �-pleated sheets and �-helical fibersave been developed [8—13]. We found a unique class ofeptides that represents the shortest reported natural, non-

romatic linear peptides (consisting of 3—7 mainly aliphaticmino acids) to form hydrogels with high mechanicaltrength. We have recently demonstrated that the self-ssembly of these peptides occurs in aqueous solution via

Ultrasmall natural peptides self-assemble to strong temperature

Figure 1 (A) Schematic representation of the peptide motifand its proposed assembly to fibers. (B) Schematic formationof single fibers by stacking of peptide monomers using Ac-LIVAGD (Ac-LD6) and Ac-AIVAGD (Ac-AD6) as model systems. (C)Schematic formation of three-dimensional scaffolds or meshes

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in the form of hydrogels by entangling of individual fibers.

transitional �-helices that transform into �-turnsupramolecular structures [14].

We observed that a specific peptide motif enables ultra-small linear peptides with 3—7 natural amino acids toself-assemble to helical fibers within strong supramolec-

ular structures. The peptide motif exhibits amphiphilicproperties, since it contains a hydrophobic tail and ahydrophilic head group (Fig. 1A). The hydrophobic tail isthe dominant part of the peptide. It involves a minimum

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-resistant helical fibers 233

f two aliphatic amino acids for a trimer peptide and aaximum of six amino acids for a heptamer (Table 1).he head group includes acidic, neutral or basic non-romatic polar amino acids, preferably at the C-terminus.he N-terminus is acetylated so as to keep it free ofharge.

The ease of self-assembly, from small aggregatesnd unstable fibers to firm meshes of stably assembledupramolecular fibrils, depends strongly on the decrease inhe hydrophobic character of the amino acid sequence ofhe hydrophobic tail (Fig. 1B and C). The assembly mostikely occurs non-covalently by molecular recognition viaarallel-antiparallel pairing [14]. Considering the assemblyrinciple, we rationally proposed and evaluated a groupf 27 self-assembling hydrogel-forming L- and D-peptidesTable 1) from a pool of more than 100 amphiphilic pep-ides. This table is by no means exhaustive, but due toime and experimental constraints, we have only assessedhese 28 candidates in great detail. We verified our hypoth-sis of the decreasing hydrophobicity profile by an alaninecan of the peptide sequence Ac-LIVAGD. By sequentiallyxchanging each amino acid of the hydrophobic tail to ala-ine, we evaluated the altered peptides on their ease ofber formation and hydrogel strength. Both criteria areeasures of the driving forces needed for fiber assem-ly and aggregation. Hexamer Ac-LIVAGD (Ac-LD6) was theest performing hydrogel in terms of ease of hydrogelormation and strength, followed by Ac-AIVAGD (Ac-AD6).he former readily formed a gel at 1 mg/mL (entrapping9.9% water), while the latter has a critical minimumoncentration of 5 mg/mL (99.5% water) (Supplementarynformation Fig. S1A). Hexamers Ac-LIVAAD and Ac-LAVAGDormed weak hydrogels, and Ac-LIAAGD failed to gel withinhe experimental time frame. Since leucine and isoleucineave comparable hydrophobicity profiles, the exchange ofoth amino acids from Ac-LIVAGD (Ac-LD6) to Ac-ILVAGDid not significantly change the ease of gel formation.he trimers Ac-IVD (Ac-ID3) and Ac-IID were the smallestmphiphilic hydrogel-forming peptides that followed ourroposed motif (Table 1). Non-aromatic dipeptides, com-osed of one aliphatic and one polar amino acids, did notorm hydrogels.

We found that the length of the hydrophobic tail andhe polarity of the head group are integral elements thatupport the ease of hydrogel formation. Hexamers typi-ally formed gels more readily than heptamers, pentamers,etramers and trimers. Better gels were also derived fromcidic (D and E) head groups, followed by neutral (S and) and basic (K) polar non-aromatic amino acids. Duringondensation, the helical fibers could be observed withhe naked eye. As the condensation proceeded, the visi-le aggregates disappeared within the solid-like hydrogels.ll investigated peptides were heat-resistant up to 90 ◦C,nd did not significantly change their conformation duringeating. Moreover, the peptides reversibly regained theirnitial conformation after cooling, as verified by circularichroism (CD) spectroscopy (Supplementary informationig. S2).

Fiber formation of the peptide hydrogels was con-rmed by low-temperature field-emission scanning elec-ron microscopy (FESEM). Interestingly, fibrous structuresFig. 2A—H) and nanostructures (Fig. 2I—L) were assembled,

234 A. Mishra et al.

Table 1 A group of 28 peptides that self-assembled to ordered supramolecular networks, resulting in hydrogel formation. Allpeptides were acetylated at the N-terminus, while the carboxyl group at the C-terminus was unchanged, except for LIVAGK,which was amidated to suppress the charge at the C-terminus. The D-isoform of some peptides (marked with *) was also studied.Peptides that were investigated more extensively are shown in bold, namely, LIVAGD (also named Ac-LD6), AIVAGD (also namedAc-AD6), and IVD (also named Ac-ID3).

Head group Heptamer Hexamer Pentamer Tetramer Trimer

Aspartic acid (D) LIVAGDD LIVAGD* LIVAD IVAD* IVD*

ILVAGD* LIVGD IIID IIDLIVAADLAVAGDAIVAGD*

Glutamic acid (E) LIVAGEE LIVAGE*

Lysine (K) LIVAGK IIIKSerine (S) LIVAGS*

ILVAGSAIVAGS

Threonine (T) LIVAGTAIVAGT

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he latter predominantly at low peptide concentrations.ven undissolved lyophilized peptide powder containedhort assembled fibers (Fig. 2P). Within the hydrogels,ong fibers of up to the millimeter scale were observedFig. 2A). The fiber diameters were approximately 50—60 nmFig. 2C—F), similar to collagen (Fig. 2G). FESEM datahowed stacked structures as building blocks for the fibersFig. 2C, E, H) and fiber condensation (Fig. 2A—D), asroposed as Fig. 1. Individual fibers revealed orderedelical turns with fixed periodicity along the fiber axisFig. 2E), as was previously confirmed by CD and X-ray fiberiffraction analyses [14]. The striking similarity of our pep-ide fibers to collagen fibers in the extracellular matrixodes well for tissue engineering applications, providingechanical support, cues for cell attachment and migra-

ion.Each peptide has a critical minimum concentration for

orming clear solid-like hydrogels in water (Supplementarynformation Fig. S1A). With increasing peptide concen-rations, the gels changed their appearance from clearo translucent to opaque white, and exhibited increas-ng rigidity (Supplementary information Fig. S1B and C).his was attributed to the fiber density and arrange-ent. For example, the hexapeptide Ac-LD6 has a critical

oncentration of 1 mg/mL, forming a clear soft gel with‘web-like’’ structures (Fig. 2Q). At higher concentrations,he opaque white gels were built up from entangled pep-ide fibers that form thick fiber bundles within the peptideetworks (Fig. 2A—D). The entire network ensemble resem-led a porous honeycomb (Fig. 2N—O), which containedarge numbers of water-holding cavities. The porous naturef the material would favor cell migration and prolifera-ion.

The majority of the peptide hydrogels demonstrated

igh mechanical strength with high storage modulus (G′)alues of up to 90 kPa (Fig. 3A). The storage modulus ofifferent peptide-derived hydrogels at a given concentra-ion varied between 103 and 105 Pa (Fig. 3A). In contrast,

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elatin (hydrolyzed collagen) at the same concentrations two orders of magnitude weaker. These values werelso significantly higher than those reported for hydro-els formed from self-assembled �-sheets [9], fibrillarnd coiled-coil gels [10,12]. Thus, the peptide-derivedydrogels would be good substrates for biomedical appli-ations to provide strong support, such as cartilage repairnd nucleus pulposus (NP) replacement in degenerativepinal disease. Raising the temperature from 25 ◦C to 50 ◦Cid not change the gel strength significantly, indicatinghe good thermal stability of these hydrogels (Fig. 3B).n contrast, gelatin melted when the temperature wasaised. As we are interested in alternative biomaterials forissue engineering applications, we compared the mechan-cal properties of Ac-LD6 (L) with a high-quality collagenel at typical concentrations used to encapsulate cellsFig. 3C). Ac-LD6 (L) demonstrated 10-fold higher mechani-al strength.

By varying the amino acid sequence, the hydrogel rigid-ty could be tuned by other factors, such as peptide andalt concentrations and pH. Increasing the peptide con-entration (Fig. 3D and E) increased the rigidity of theydrogels. The same general trend was observed for theexamer and trimer, although a higher concentration ofhe trimer Ac-ID3 (L) was needed for gelation due to itshorter hydrophobic tail. Furthermore, a three-fold higheroncentration of Ac-ID3 (L) was needed to attain similarel strengths. The gel morphology also changed with pep-ide concentration as observed by FESEM (Supplementarynformation Fig. S3). As expected, less fibers were observedt lower peptide concentrations, giving rise to a ‘‘spider-eb’’ like structures. Increasing the salt concentration from0 mM to 150 mM of NaCl (Fig. 3F) reduced the mechanicaltrength.

The biocompatibility of the hydrogels and their effectn cell proliferation were studied using a variety of cellypes. The viability of human mesenchymal stem cellshMSCs) decreased with peptide concentration (Fig. 4A and

Ultrasmall natural peptides self-assemble to strong temperature-resistant helical fibers 235

Figure 2 Morphological characterization of the peptide hydrogel scaffolds by FESEM. (A—L, N—R) FESEM images of different struc-tures formed from different self-assembling peptides. Condensed fibers of (A, B) Ac-ID3 (L) (15 mg/mL), (C) Ac-ID3 (L) (20 mg/mL)and (D) Ac-LD6 (L) (15 mg/mL). Single fibers of (E, F) Ac-AD6 (L) (20 mg/mL), (G) Type I collagen (1.54 mg/mL), and (H) Ac-LD6 (L)(1 mg/mL). Nanostructures formed from (I, J) Ac-AD6 (L) (5 mg/mL), (K, L) Ac-LD6 (L) (0.1 mg/mL). (M) Confocal microscopy imageof self-assembled fibers derived from 10 mg/mL of Ac-ID3 (L) in water. Scale bar = 25 �m. (N, O) Porous honeycomb structures atdifferent magnification derived from 20 mg/mL of hexamer Ac-AD6 (D). (P) Fiber structures were observed in the powder of freshlysynthesized, still undissolved lyophilized Ac-LD6 (L). Spiderweb-like structures were formed at a low concentration of (Q) Ac-LD6

(L) (1 mg/mL) and (R) collagen I (1.5 mg/mL).

236 A. Mishra et al.

Figure 3 High mechanical strength was demonstrated for the majority of the peptide-derived hydrogels. (A, B) Storage moduli (G′)of different hydrogels (20 mg/mL) as a function of angular frequency under 0.1% strain, at 25 ◦C and 50 ◦C, respectively (n = 3). Thegels demonstrated good thermal stability compared to gelatin (20 mg/mL), which liquidified at 50 ◦C. (C) G′ of hydrogels derivedfrom Ac-LD6 (L) (2.5 mg/mL) and Type I collagen (2.5 mg/mL) at 25 ◦C (n = 3). Increasing peptide concentration increased G′ ofhydrogels derived from (D) Ac-LD6 (L) and (E) Ac-ID3 (L). (F) Increasing NaCl salt concentration decreased G′ of hydrogels derivedf

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rom 10 mg/mL of Ac-LD6 (L).

upplementary information Fig. S6A). This could be due tohe increasing acidity of the media, since neutralizationf the culture media to pH 7 restored metabolic activityFig. 4B and Supplementary information Fig. S6A). Of theeptides evaluated, hexamer Ac-LD6 (L) was highly biocom-atible, better than the D-isoform. Tripeptide Ac-ID3 (L) hadhe lowest IC50, due to its lowest pH from the presence ofore carboxylic groups per gram of peptide. The same trendas observed for rabbit retinal pigment epithelial (rRPE)ells and for porcine nucleus pulposus (pNP) cells (Fig. 4Dnd Supplementary information Fig. S6B). To date, we haveuccessfully cultured a variety of other mammalian primaryells on these peptide hydrogels, including human primaryenal tubular cells, human umbilical vein endothelial cells,at hepatic stellate cells, and rabbit fibroblasts. All cells tol-rated the peptide-derived hydrogels well, which would beromising for applying the latter towards tissue regenerationurposes, especially as injectable artificial alternative forell—matrix compounds. Preliminary studies demonstratedhat the hydrogels derived from neutralized peptides werelso non-hemolytic (Fig. 4C), which would bode well forn vivo applications.

We also performed rheological measurements with theP from porcine lumbar spinal discs. The NP is the innerart of the spinal intervertebral disc, a jelly-like materialhat absorbs vertical pressure exerted by gravity, and con-ers flexibility to the spinal column as a whole. With geltrengths on the order of 100 Pa (Supplementary information

ig. S7), pNP storage moduli values are significantly lowerhan that of other species reported elsewhere [15—17], butre not directly comparable, due to the use of different

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nimals, instruments, methods and conditions. The storageoduli of human lumbar NP is ∼2—5 kPa, as measured under

imilar conditions [15]. The variation could be attributedo human NP having to support greater compressive forcesue to our upright posture. In comparison, our peptide-erived hydrogels, which was stiffer than pNP by two ordersf magnitude, have similar gel strengths to human NP, andould thus serve as an injectable therapy or as a componentf a biocompatible intervertebral disc prosthesis to treategenerative intervertebral disc. Degenerative disc diseases currently the predominant cause of disability amongsthe adult population, affecting 85% of the population byhe age of 50. There is a huge unmet clinical need for discrosthesis that can inhibit or repair early-stage disc dam-ge.

Our results on the peptide hydrogels’ biocompatibilityowards primary cells, especially pNP cells and hMSCs sug-ested that these new materials would be suitable for tissueegeneration in orthopedic and plastic surgery. These hydro-els might also meet the demands for new patient-tailoredissues, such as cartilages, blood vessels and nerve tissue,s well as for wound healing and grafting.

Self-assembly of peptide molecules as building blocksor a bottom-up fabrication of biomaterial is of signif-cant and increasing importance due to their inherentiological specificity. Short natural peptides have the advan-age of combining chemical diversity and biocompatibilityith a facile synthesis at the large scale. Herein we

eported the discovery of a remarkably self-driven assem-ly of natural ultrasmall predominantly aliphatic peptidemphiphiles (3—7 mers) to high-strength fibrous structures

Ultrasmall natural peptides self-assemble to strong temperature-resistant helical fibers 237

Figure 4 Biocompatibility of the peptide-derived hydrogels. (A, B) Increasing peptide concentration decreased human mesenchy-mal stem cell (hMSC) viability after 48 h by increasing acidity (n = 5). Hydrogel derived from Ac-LD6 (L) was least cytotoxic, whilethat from Ac-ID3 (L) has the lowest IC50. The D-isoform was less biocompatible. Neutralizing the acidity of 10 mg/mL Ac-LD6 (L)improved the cell viability of the peptide-derived hydrogels, particularly for rabbit retinal epithelial cells. (C) Increasing peptideconcentration resulted in increasing hemolysis of the peptide-derived hydrogels (n = 5). This could be attributed to the acidity asPBS at pH 3 also lysed 20% of the red blood cells as compared to 1% Triton-X. When neutralized to pH 7.3, the peptide-derivedhydrogels demonstrated negligible hemolysis. (D) Viability of different cell types after 30 h of exposure to hydrogels derived from

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different Ac-LD6 (L) concentrations. Scale bar = 25 �m.

in aqueous solutions. The fibers were visible in the lightmicroscope. Depending upon the peptide concentration,these fibers would organize themselves to hydrogels witha water content of up to 99.9%. We would be exploitingthe physical properties and biocompatibility of these newmaterials for regenerative application in spine degenerationand cartilage replacement. In this prospect, the peptide-based supramolecular structures might act as functionalsubstitutes for the extracellular matrix or collagen-likestructures.

Production of biomaterials from ultrashort self-

assembling peptides would offer an attractive and low-costalternative for the manufacture of biomimetic structuresin a wide range of applications. In particular, naturalpeptide-based hydrogels would attract high interest due

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o their biomimetic origin and well-defined syntheticature. We have demonstrated that our new class ofelf-assembling peptides exhibited interesting propertieshat would provide alternatives to the existing diverseange of self-assembling peptides. These unique propertiesould offer new possible applications of peptide-basediomaterials in the fields of bioengineering, tissue engi-eering, drug delivery, nanotechnology and surfacecience.

cknowledgement

e thank Ulung Khoe and Furen Zhuang for their helpith CD spectra and sample preparation for FESEM. Ulung

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hoe designed the schematic drawings of the peptidessembly. This work was supported by the Institute ofioengineering and Nanotechnology (Biomedical Researchouncil, Agency for Science, Technology and Research,ingapore).

ppendix A. Supplementary data

upplementary data associated with this arti-le can be found, in the online version, atoi:10.1016/j.nantod.2011.05.001.

eferences

[1] R. Langer, D.A. Tirrell, Nature 428 (2004) 487—492.[2] S.G. Zhang, Nat. Biotechnol. 21 (2003) 1171—1178.[3] Y. Yang, U. Khoe, X. Wang, A. Horii, H. Yokoi, S. Zhang, Nano

Today 4 (2009) 193—210.[4] J.M. Lehn, Science 295 (2002) 2400—2403.[5] C.A.E. Hauser, S.G. Zhang, Chem. Soc. Rev. 39 (2010)

2780—2790.[6] E.S. Place, N.D. Evans, M.M. Stevens, Nat. Mater. 8 (2009)

457—470.[7] A.R. Hirst, B. Escuder, J.F. Miravet, D.K. Smith, Angew. Chem.

Int. Ed. 47 (2008) 8002—8018.[8] S.G. Zhang, T. Holmes, C. Lockshin, A. Rich, Proc. Natl. Acad.

Sci. U.S.A. 90 (1993) 3334—3338.[9] A. Aggeli, M. Bell, N. Boden, J.N. Keen, P.F. Knowles, T.C.B.

McLeish, M. Pitkeathly, S.E. Radford, Nature 386 (1997)259—262.

10] W.A. Petka, J.L. Harden, K.P. McGrath, D. Wirtz, D.A. Tirrell,Science 281 (1998) 389—392.

11] C. Wang, R.J. Stewart, J. Kopecek, Nature 397 (1999) 417—420.

12] E.F. Banwell, E.S. Abelardo, D.J. Adams, M.A. Birchall, A. Cor-rigan, A.M. Donald, M. Kirkland, L.C. Serpell, M.F. Butler, D.N.Woolfson, Nat. Mater. 8 (2009) 596—600.

13] S. Zhang, M.G. Greenfield, A. Mata, L.C. Palmer, R. Bitton, J.R.Mantei, C. Aparicio, M.O. de la Cruz, S.I. Stupp, Nat. Mater. 9(2010) 594—601.

14] C. Hauser, R. Deng, A. Mishra, Y. Loo, U. Khoe, F. Zhuang, D.Cheong, A. Accardo, M. Sullivan, C. Riekel, J.Y. Ying, U. Hauser,Proc. Natl. Acad. Sci. U.S.A. 108 (2011) 1361—1366.

15] J.C. Iatridis, L.A. Setton, M. Weidenbaum, V.C. Mow, J.Biomech. 30 (1997) 1005—1013.

16] J.C. Leahy, D.W.L. Hukins, J. Mater. Sci. Med. 12 (2001)689—692.

17] J.I. Boxberger, A.S. Orlansky, S. Sen, D.M. Elliott, J. Biomech.42 (2009) 1941—1946.

Archana Mishra received her B. Pharm. andM. Pharm. from the faculty of technology,S.N.D.T. Women’s University, Mumbai, India in2003 and 2006 respectively. Upon graduation,she worked in 2006—2007 on a collaborativeproject between Panacea biotech and C.U.Shah College of Pharmacy (India), designingand developing novel drug delivery systems.She moved to Singapore and worked as a

research assistant under Prof. Tanja Weil atthe National University of Singapore. Cur-

ently, she is a Lab Officer at the Institute of Bioengineeringnd Nanotechnology. Her research interest includes working on

acir

A. Mishra et al.

herapeutic proteins and peptides, biomaterials, designing andeveloping novel drug and gene delivery systems, biosensingevices.

Yihua Loo received her B.Sc. and Ph.D. inBiomedical Engineering from The Johns Hop-kins University and Johns Hopkins MedicalInstitute, respectively. During the course ofher graduate studies, she also spent time atDuke University as a visiting graduate student.Following her graduation in 2010, she joinedthe Institute of Bioengineering and Nano-technology as a Postdoctoral Fellow, workingon developing peptide-based hydrogels forregenerative medicine. Her scientific inter-

sts include non-viral gene delivery, application of stem cellsowards patient-tailored therapies, peptide and polymer-peptideydrogels.

Rensheng Deng received his B.E. and Ph.D.in Chemical Engineering from Tsinghua Uni-versity, China in 1996 and 2001, respectively.He worked as a Research Fellow at theSingapore-MIT Alliance from 2001 to 2004and a Postdoctoral Associate at the Mas-sachusetts Institute of Technology from 2004to 2006. After that, he joined the Instituteof Bioengineering and Nanotechnology as aresearch scientist and served as a projectleader. His research interests include fluid

echanics, mass and heat transfer, biomaterials and membraneechnology. He is currently a scientist for computational fluidynamics in the Global R&D Center of Siemens Water Technologies,ingapore.

Yon Jin Chuah graduated from Universityof Western Australia with a Bachelor ofScience (Molecular Biology and Biotechnol-ogy), and received the UWA/PSB AcademyBachelor of Science Life Sciences Prizes(Transnational) in 2010. He embarked onhis research career with Associate Profes-sor Hwan Tak Hee in National University ofSingapore since 2007. His research inter-ests include molecular basis of intervertebraldisc degeneration and regeneration, using

olecular, histological, scanning electron microscopy and surgicalechniques.

Hwan Tak Hee is a fellowship trained spinesurgeon who completed his medical degreein National University of Singapore in 1990,and obtained his postgraduate degrees insurgery in Royal Collage of Surgeons of Glas-gow and Edinburgh in 1995. He joined theNational University Hospital in 2000 as anAssociate Consultant, and is currently SeniorConsultant and Deputy Head of the Divi-sion of Spinal Surgery at the Departmentof Orthopaedic Surgery. He joined the Yong

oo Lin School of Medicine, National University of Singapore

s an Assistant Professor in 2002, and was promoted to Asso-iate Professor in 2008. Prof. Hee’s research interests aren the basic science of intervertebral disc degeneration andegeneration.

ture

uPobMSdation. Her research covers small peptides and peptidomimeticsfor developing novel biomaterials and therapeutics, and the use

Ultrasmall natural peptides self-assemble to strong tempera

Prof. Jackie Y. Ying received her B.E. andPh.D. from The Cooper Union and Prince-ton University, respectively. She joined thefaculty at Massachusetts Institute of Tech-nology in 1992, where she was Professor ofChemical Engineering until 2005. She hasbeen the Executive Director of the Insti-tute of Bioengineering and Nanotechnologyin Singapore since 2003. For her research onnanostructured materials, Prof. Ying has beenrecognized with the American Ceramic Soci-

ety Ross C. Purdy Award, David and Lucile Packard Fellowship, Officeof Naval Research and National Science Foundation Young Inves-tigator Awards, Camille Dreyfus Teacher-Scholar Award, AmericanChemical Society Faculty Fellowship Award in Solid-State Chem-istry, Technology Review TR100 Young Innovator Award, AmericanInstitute of Chemical Engineers (AIChE) Allan P. Colburn Award, andSingapore National Institute of Chemistry-BASF Award in MaterialsChemistry. Prof. Ying was elected a World Economic Forum Young

Global Leader, and a member of the German National Academy ofSciences, Leopoldina. She was named one of the ‘‘One HundredEngineers of the Modern Era’’ by AIChE in its Centennial Celebration.She is the Editor-in-Chief of Nano Today.

od

-resistant helical fibers 239

Charlotte A.E. Hauser received her Diplomain Chemistry at the University of Cologne,Germany, and did her Ph.D. studies at theMassachusetts Institute of Technology, USA.Afterwards, she joined INSERM in Paris,France, and the Max—Planck-Institute of Psy-chiatry in Munich, Germany. She is currentlya Team Leader and Principal Research Sci-entist at the Institute of Bioengineering andNanotechnology (IBN). Since her Habilitationin 2004, she has been an external fac-

lty member of the Medical University of Luebeck, Germany.rior to joining IBN, she was Founder and Managing Directorf Octagene, Martinsried/Munich, Germany. Her research haseen recognized by several awards from the German Federalinistry of Science and Technology (BMFT Award), the Frenchociete des Amis des Science, and the Bavarian Research Foun-

f G-protein coupled receptors for drug screening and biosensorevelopment.