Co-reporter:Mridul Sarker, Nikodem Tomczak, and Sierin Lim
ACS Applied Materials & Interfaces March 29, 2017 Volume 9(Issue 12) pp:11193-11193
Publication Date(Web):March 14, 2017
DOI:10.1021/acsami.6b14349
Encapsulation of active compounds in Pickering emulsions using bioderived protein-based stabilizers holds potential for the development of novel formulations in the fields of foods and cosmetics. We employ a dodecahedron hollow protein nanocage as a pH-switchable Pickering emulsifier. E2 protein nanocages are derived from pyruvate dehydrogenase multienzyme complex from Geobacillus stearothermophilus which adsorb at the oil/water interface at neutral and basic pH’s and stabilize the Pickering emulsions, while in the acidic range, at pH ∼4, the emulsion separates into emulsion and serum phases due to flocculation. The observed process is reversible for at least five cycles. Optimal formulation of a Pickering emulsion composed of rosemary oil, an essential oil, and water has been achieved by ultrasonication and results in droplets of approximately 300 nm in diameter with an oil/water ratio of 0.11 (v/v) and 0.30–0.35% (wt %). Ionic stabilization is observed for concentrations up to 250 mM NaCl and pH values from 7 to 11. The emulsions are stable for at least 10 days when stored at different temperatures up to 50 °C. The resulting Pickering emulsions of different compositions also form a gel-like structure and show shear thinning behavior under shear stress at a higher oil/water ratio.Keywords: emulsion gel-like structure; pH-switchable; Pickering emulsion; protein nanocage; rheological analysis;
Co-reporter:Tao Peng, Hwankyu Lee and Sierin Lim
Biomaterials Science 2015 vol. 3(Issue 4) pp:627-635
Publication Date(Web):09 Feb 2015
DOI:10.1039/C4BM00313F
Controlling the self-assembly behavior of caged proteins expands their potential applications in nanotechnology. While the structure of a caged E2 protein from pyruvate dehydrogenase is inert to any pH change, the incorporation of switchable GALA peptide that undergoes a coil-to-helix transition at acidic pH modulates its self-assembly property. By substituting the native α-helix at the C-terminus of the E2 protein with the GALA peptide, we report the first engineered caged protein with reversible inversed pH-responsive behavior. The redesigned caged E2 protein assumes an assembly profile that is distinct from the native state; it disassembles at pH 7.0 and self-assembles at pH 4.0 in a reversible manner. This unique reversible pH trigger suggests the applicability of the self-assembly control on other multi-subunit macromolecules.
Co-reporter:Herlina Arianita Dewi, Gengzhi Sun, Lianxi Zheng and Sierin Lim
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 5) pp:3435-3440
Publication Date(Web):22 Dec 2014
DOI:10.1039/C4CP04575K
Charge separation in photosynthetic light reactions has gained much interest in an attempt to fabricate biological photovoltaic devices through integration of photosynthetic material and conducting electrodes. Direct interaction between thylakoids, as representatives of photosynthetic materials, and multi-walled carbon nanotubes (MWCNTs) is expected to increase charge transfer. Thylakoids are isolated from spinach leaf chloroplasts and pristine MWCNTs are dispersed in Triton X-100 (TX-100) as a surfactant to retain their electronic properties through non-covalent interactions. The Raman and UV-Vis spectra suggest close interactions between the thylakoids and the MWCNTs. Stable thylakoids including the embedded protein subunits and light harvesting antennas can be detected from the non-shifted 680 nm absorbance peak. The 50% fluorescence quenching in the MWCNTs-thylakoids preparation as compared to thylakoids alone using single wavelength excitation suggests charge transfer between the thylakoids and the MWCNTs.
Co-reporter:Jakob W. Buecheler;Christopher B. Howard;Christopher J. de Bakker;Stephen Goodall;Martina L. Jones;Thinzar Win;Tao Peng;Cher Heng Tan;Akhil Chopra;Stephen M. Mahler
Journal of Chemical Technology and Biotechnology 2015 Volume 90( Issue 7) pp:1230-1236
Publication Date(Web):
DOI:10.1002/jctb.4545
Abstract
BACKGROUND
A range of protein-based nanoparticles has been developed for cancer drug delivery and diagnostics. This includes the E2 protein derived from the pyruvate dehydrogenase complex in Geobacillus stearothermophilus which assembles into a 60-subunit protein cage structure that is capable of encapsulating cancer therapeutics. In this study antibody fragments targeting the epidermal growth factor receptor (EGFR) were tethered to the surface of E2 protein nanoparticles to determine whether the protein nanoparticles could be specifically targeted to EGFR overexpressing cancer cells.
RESULTS
Variants of the anti-EGFR antibody fragment and the E2 protein containing specific cysteine residues (E2ΔN17A186C) were conjugated using a maleimide-specific crosslinker. Electron microscopy and dynamic light scattering analysis indicated that the cysteine modified E2 protein correctly assembled into a 25–30 nm particle. The conjugation of the anti-EGFR antibody fragment (26 kDa) with a subunit of the E2 protein (26 kDa) was confirmed by mass spectrometry with an estimated molecular weight of 52 kDa. The binding of the conjugated E2 particle to native EGFR on MDA MB 231 cells and recombinant EGFR was confirmed using flow cytometry and biolayer interferometry, respectively.
CONCLUSIONS
In this study, proof-of-principle that an EGFR-targeting scFv can be stably conjugated to the cysteine variant E2ΔN17A186C protein nanoparticle without loss of targeting capability has been demonstrated. Conceptually scFv antibody fragments reactive with other important cancer targets could be utilized and presents the opportunity for generation of multi-targeted protein nanoparticles by conjugating various scFvs with different specificities on the same particle. © 2014 Society of Chemical Industry
Co-reporter:Herlina Arianita Dewi, Fanben Meng, Barindra Sana, Chunxian Guo, Birgitta Norling, Xiaodong Chen and Sierin Lim
RSC Advances 2014 vol. 4(Issue 90) pp:48815-48820
Publication Date(Web):06 Oct 2014
DOI:10.1039/C4RA07070D
The electrons generated by photosynthetic water splitting have been studied for direct electron transfer under light irradiation. Isolated thylakoids are incorporated as biocatalysts with indium tin oxide (ITO) as the electrode in a two-chamber photosynthetic electrochemical cell (PEC). The generated photocurrent is compared between deposited and dispersed thylakoids. The physical properties of deposited thylakoids are observed using field emission scanning electron microscopy (FESEM) and absorbance spectroscopy techniques. The results show the presence of thylakoids with bound photosystems including light harvesting antennas and other protein complexes. Further investigations reveal that the direction of electron transfer can be tuned by varying the applied potentials to promote bi-directional photocurrent. The maximum cathodic photocurrent is obtained at 50 mV vs. standard calomel electrode (SCE), while the maximum anodic photocurrent is enhanced with increasing positive potential applied. Our observation indicates the possibility of either reduction of O2 or H2O2 as the prominent cathodic photocurrent source, while electron transfer from thylakoids to ITO yields the anodic photocurrent.
Co-reporter:Kelsen Bastari;Mohamed Arshath
Journal of Materials Science: Materials in Medicine 2014 Volume 25( Issue 3) pp:747-757
Publication Date(Web):2014 March
DOI:10.1007/s10856-013-5125-9
Ceramic-polymer hybrid particles, intended for osteomyelitis treatment, were fabricated by preparing poly(lactic-co-glycolic acid) particles through an emulsion solvent evaporation technique, followed by calcium phosphate (CaP) coating via a surface adsorption-nucleation method. The presence of CaP coating on the surface of the particles was confirmed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Subsequently, two antibiotics for treating bone infection, nafcillin (hydrophilic) and levofloxacin (amphiphilic), were loaded into these hybrid particles and their in vitro drug release studies were investigated. The CaP coating was shown to reduce burst release, while providing sustained release of the antibiotics for up to 4 weeks. In vitro bacterial study against Staphylococcus aureus demonstrated the capability of these antibiotic-loaded hybrid particles to inhibit biofilm formation as well as deteriorate established biofilm, making this hybrid system a potential candidate for further investigation for osteomyelitis treatment.
Co-reporter:Huajun Qiu, Xiaochen Dong, Barindra Sana, Tao Peng, David Paramelle, Peng Chen, and Sierin Lim
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 3) pp:782
Publication Date(Web):January 18, 2013
DOI:10.1021/am3022366
The monolithic three-dimensional (3D) graphene network is used as the support for Pt nanoparticles (NPs) to fabricate an advanced 3D graphene-based electrocatalyst. Distinct from previous strategies, the monodispersed Pt NPs with ultrafine particle size (∼3 nm) are synthesized using ferritin protein nanocages as the template and subsequently self-assembled on the 3D graphene by leveraging on the hydrophobic interaction between the ferritin and the graphene. Following the self-assembly, the ferritins are removed, resulting in a stable Pt NP/3D graphene composite. The composite exhibits much enhanced electrocatalytic activity for methanol oxidation as compared with both Pt NP/chemically reduced graphene oxide (Pt/r-GO) and state-of-the-art Pt/C catalyst. The observed electrocatalytic activity also shows marked improvement over Pt/3D graphene prepared by pulse electrodeposition of Pt. This study demonstrates that protein nanocage templating and assembly are promising strategies for the fabrication of functional composites in catalysis and fuel cell applications.Keywords: ferritin; fuel cells; protein nanocage; Pt electrocatalyst; three-dimensional graphene;
Co-reporter:Barindra Sana, Chueh Loo Poh and Sierin Lim
Chemical Communications 2012 vol. 48(Issue 6) pp:862-864
Publication Date(Web):29 Nov 2011
DOI:10.1039/C1CC15189D
T
2 contrast is gaining importance in high field strength MRI. We report a strategy for developing a T2 contrast agent from paramagnetic metal ions synthesized within an engineered protein cage. The manganese–ferritin nanocomposite showed high T2 relaxivity indicating its potential as an ultrasensitive T2 contrast agent.
Co-reporter:Yan Li;Chui Ping Ooi
Pharmaceutical Research 2012 Volume 29( Issue 3) pp:756-769
Publication Date(Web):2012 March
DOI:10.1007/s11095-011-0600-9
To reduce the toxicity and achieve a sustainable and controllable release of cisplatin (CDDP).CDDP was loaded onto Fe5 (Fe3+ doped hydroxyapatite at atomic ratio of Feadded/Caadded = 5%) nanoparticles through surface adsorption. Subsequently, CDDP-loaded Fe5 nanoparticles (CDDP-Fe5) and/or CDDP were encapsulated into poly(lactide-co-glycolide) (PLGA) microspheres using oil-in-water single emulsion. Drug release profiles and degradation behaviors were monitored.CDDP-Fe5 demonstrated a high initial burst (42% on day 1) and short release time (25 days) as CDDP was directly released from Fe5 nanoparticles. CDDP-Fe5 encapsulated within the PLGA microspheres revealed a lower initial burst (23% on day 1) and longer release time (55 days) than CDDP-Fe5. Compared with PLGA microspheres containing only CDDP, which showed typical biphasic release manner, microspheres with CDDP-Fe5 and CDDP demonstrated a nearly linear release after the initial burst. Fe5 and CDDP delayed microsphere degradation. All samples became porous, disintegrated, fused, and formed pellets at the end of the study.Fe5/PLGA composite microspheres showed favorable CDDP release behavior compared to microspheres composed of polymer alone, suggesting its potential as a new CDDP formulation.
Co-reporter:Tao Peng, Hwankyu Lee, and Sierin Lim
Biomacromolecules 2012 Volume 13(Issue 3) pp:
Publication Date(Web):February 9, 2012
DOI:10.1021/bm201587q
Understanding the self-assembly mechanism of caged proteins provides clues to develop their potential applications in nanotechnology, such as a nanoscale drug delivery system. The E2 protein from Bacillus stearothermophilus, with a virus-like caged structure, has drawn much attention for its potential application as a nanocapsule. To investigate its self-assembly process from subunits to a spherical protein cage, we truncate the C-terminus of the E2 subunit. The redesigned protein subunit shows dynamic transition between monomer and trimer, but not the integrate 60-mer. The results indicate the role of the trimer as the intermediate and building block during the self-assembly of the E2 protein cage. In combination with the molecular dynamics simulations results, we conclude that the C-terminus modulates the self-assembly of the E2 protein cage from trimer to 60-mer. This investigation elucidates the role of the intersubunit interactions in engineering other functionalities in other caged structure proteins.
Co-reporter:Tao Peng and Sierin Lim
Biomacromolecules 2011 Volume 12(Issue 9) pp:
Publication Date(Web):July 28, 2011
DOI:10.1021/bm2005438
Limited studies have been done on the interactions between subunits of self-assembling protein cages. E2 protein cage from Bacillus stearothermophilus was investigated in this work to impart pH-sensitive disassembly profile. Key amino acids were identified at the intratrimer and intertrimer interfaces, and histidine residues were introduced to these key sites to probe for their influences on the E2 assembly. We found that both the intratrimer- and the intertrimer-modified mutant proteins have the same quaternary structures as the wild type (E2-WT) at physiological pH of 7.4. At pH 5.0, the intratrimer-modified protein maintained its spherical structure. In contrast, the intertrimer modified protein lost its integrity, as observed under the electron microscope, whereas it remained soluble and nondenatured. The identified interactions between the intertrimers are critical in the formation of E2 protein cage. The pH-controlled disassembly of E2 protein cage in soluble and nondenatured form make it promising in nanoscale applications, especially for drug delivery and release in the endosomes.
Co-reporter:Herlina Arianita Dewi, Gengzhi Sun, Lianxi Zheng and Sierin Lim
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 5) pp:NaN3440-3440
Publication Date(Web):2014/12/22
DOI:10.1039/C4CP04575K
Charge separation in photosynthetic light reactions has gained much interest in an attempt to fabricate biological photovoltaic devices through integration of photosynthetic material and conducting electrodes. Direct interaction between thylakoids, as representatives of photosynthetic materials, and multi-walled carbon nanotubes (MWCNTs) is expected to increase charge transfer. Thylakoids are isolated from spinach leaf chloroplasts and pristine MWCNTs are dispersed in Triton X-100 (TX-100) as a surfactant to retain their electronic properties through non-covalent interactions. The Raman and UV-Vis spectra suggest close interactions between the thylakoids and the MWCNTs. Stable thylakoids including the embedded protein subunits and light harvesting antennas can be detected from the non-shifted 680 nm absorbance peak. The 50% fluorescence quenching in the MWCNTs-thylakoids preparation as compared to thylakoids alone using single wavelength excitation suggests charge transfer between the thylakoids and the MWCNTs.
Co-reporter:Tao Peng, Hwankyu Lee and Sierin Lim
Biomaterials Science (2013-Present) 2015 - vol. 3(Issue 4) pp:NaN635-635
Publication Date(Web):2015/02/09
DOI:10.1039/C4BM00313F
Controlling the self-assembly behavior of caged proteins expands their potential applications in nanotechnology. While the structure of a caged E2 protein from pyruvate dehydrogenase is inert to any pH change, the incorporation of switchable GALA peptide that undergoes a coil-to-helix transition at acidic pH modulates its self-assembly property. By substituting the native α-helix at the C-terminus of the E2 protein with the GALA peptide, we report the first engineered caged protein with reversible inversed pH-responsive behavior. The redesigned caged E2 protein assumes an assembly profile that is distinct from the native state; it disassembles at pH 7.0 and self-assembles at pH 4.0 in a reversible manner. This unique reversible pH trigger suggests the applicability of the self-assembly control on other multi-subunit macromolecules.
Co-reporter:Barindra Sana, Chueh Loo Poh and Sierin Lim
Chemical Communications 2012 - vol. 48(Issue 6) pp:NaN864-864
Publication Date(Web):2011/11/29
DOI:10.1039/C1CC15189D
T
2 contrast is gaining importance in high field strength MRI. We report a strategy for developing a T2 contrast agent from paramagnetic metal ions synthesized within an engineered protein cage. The manganese–ferritin nanocomposite showed high T2 relaxivity indicating its potential as an ultrasensitive T2 contrast agent.
![4-Thia-1-azabicyclo[3.2.0]heptane-2-carboxylicacid, 6-[[(2-ethoxy-1-naphthalenyl)carbonyl]amino]-3,3-dimethyl-7-oxo-,(2S,5R,6R)-](http://img.cochemist.com/ccimg/200/147-52-4.png)
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