Publications

In Press
Yetisen, A. K. ; Martinez, J. L. ; Unal, B., ; Khademhosseini, A. ; Butt, H. Wearables in Medicine. Advanced Materials. DOI: 10.1002/adma.201706910 In Press.
2018
Jiang, N. ; Ying, G. L. ; Yetisen, A. K. ; Shen, L. ; Cao, J. ; Busscher, H. J. ; Yang, X. Y. ; Su, B. L. A Bilayered Nanoshell for Durable Protection of Single Yeast Cells Against Multiple, Simultaneous Hostile Challenges. Chemical Science, DOI: 10.1039/C8SC01130C 2018. Publisher's Version
Elsherif, M. ; Hassan, M. U. ; Yetisen, A. K. ; Butt, H. Wearable Contact Lens Biosensors for Continuous Glucose Monitoring using Smartphones. ACS Nano, DOI: 10.1021/acsnano.8b00829 2018. Publisher's Version
Alqurashi, T. ; A., A. ; Yetisen, A. K. ; Butt, H. Laser Inscription of Pseudorandom Microstructures for Microphotonic Diffuser Applications. Nanoscale 2018.
Badawy, A. R. ; Hassan, M. U. ; Elsherif, M. I. ; Yetisen, A. K. ; Butt, H. Contact Lenses for Color Blindness. Advanced Healthcare Materials, DOI: 10.1002/adhm.201800152 (2018) 2018. Publisher's Version
Liu, Q. ; Liu, D. ; Jiang, N. ; Ying, G. ; Shi, Q. ; Yetisen, A. K. ; Liu, H. ; Fan, Y. Monodispersed silk fibroin microdroplets for protein stabilization. Applied Physics Letters 2018, 112, 173701. Publisher's Version
AlQattan, B. ; A.K., Y. ; Butt, H. Direct Laser Writing of Nanophotonic Structures on Contact Lenses. ACS Nano 2018. Publisher's Version
Elsherif, M. ; Hassan, M. U. ; Yetisen, A. K. ; Butt, H. Glucose Sensing with Phenylboronic Acid Functionalized Hydrogel Based Optical Diffusers. ACS Nano 2018. Publisher's VersionAbstract
Phenylboronic acids (PBAs) have emerged as synthetic receptors that can reversibly bind to cis diols of glucose molecules. The incorporation of phenylboronic acids in hydrogels offer exclusive attributes as the binding process with glucose induces Donnan osmotic pressure resulting in volumetric changes in the matrix. However, their practical applications are hindered because of complex readout approaches and their time-consuming fabrication processes. Here, we demonstrate a microimprinting method to fabricate densely-packed concavities in phenylboronic acid functionalized hydrogel films. A microengineered optical diffuser structure was imprinted on a phenylboronic acid based cis-diol recognizing motif prepositioned in a hydrogel film. The diffuser structure engineered on the hydrogel was based on laser inscribed arrays of imperfect microlenses that focused the incoming light at different focal lengths and direction resulting in a diffused profile of light in transmission and reflection readout modes. The signature of the dimensional modulation was detected in terms of changing focal lengths of the microlenses due to the volumetric expansion of the hydrogel that altered the diffusion spectra and transmitted beam profile. The transmitted optical light spread and intensity through the sensor was measured to determine variation in glucose concentrations at physiological conditions. The sensor was integrated in a contact lens and placed over an artificial eye. Artificial stimulation of variation in glucose concentration allowed quantitative measurements using a smartphone’s photodiode. A smartphone app was utilized to convert the received light intensity to quantitative glucose concentration values. The developed sensing platform offers low cost, rapid fabrication, and easy detection scheme as compared to other optical sensing counterparts. The presented detection scheme may have applications in wearable real-time biomarker monitoring devices at point-of-care settings.
Geng, W. ; Wang, L. ; Jiang, N. ; Cao, J. ; Li, Y. ; Xiao, Y. X. ; Wei, H. ; Yetisen, A. K. ; Yang, X. Y. ; Su, B. L. Hybrid single-cells: functionalization of living cells with nanomaterials. Nanoscale, DOI: 10.1039/C7NR08556G 2018. Publisher's VersionAbstract
Inspired by the characteristics of cells in live organisms, new types of hybrids have been designed comprising live cells and abiotic materials having a variety of structures and functionalities. The major goal of these studies is to uncover hybridization approaches that promote cell stabilization and enable the introduction of new functions into living cells. Single-cells in nanoshells have great potential in a large number of applications including bioelectronics, cell protection, cell therapy, and biocatalysis. In this review, we discuss the results of investigations that have focused on the synthesis, structuration, functionalization, and applications of these single-cells in nanoshells. We describe synthesis methods to control the structural and functional features of single-cells in nanoshells, and further develop their applications in sustainable energy, environmental remediation, green biocatalysis, and smart cell therapy. Perceived limitations of single-cells in nanoshells have been also identified.
Rashid, I. ; Hassan, M. U. ; Akhandwala, A. ; Ameen, R. M. ; Yetisen, A. K. ; Dai, Q. ; Butt, H. Structural Coloration in Caloenas Nicobarica Pigeons and Refractive Index Modulated Sensing. Advanced Optical Materials. DOI: 10.1002/adom.201701218 2018.Abstract
The Nicobar pigeon (Caloenas Nicobarica) belongs to the extinct dodo-bird family and has been declared as an endangered species. Here, microscopic and spectroscopic measurements are carried out on the bird's feathers to study the structural coloration originating from the barbule nanostructures. A range of color shades is recorded with changing viewing and illumination angles at different locations of the feathers. A spectacular variation in colors is generated by photonic structures; red, green, and blue and their blends are observed. Hydrophobicity of the optical material is also investigated. A contact angle of ≈156° is observed demonstrating it to be superhydrophobic. Experimental observations of the optical properties are analyzed on these feathers for sensing made possible due to the material and structural properties at the interface between barbule's surface and solution. An optical response is observed with a redshift in optical spectra with increasing refractive index of the solution, which is correlated with concentration values. The structural coloration in Nicobar pigeon can be adopted for many practical applications such as color selective filters, nonreflecting coatings, and refractive index-based sensing.
Alqurashi, Y. ; Bajgrowicz-Cieslak, M. ; Hassan, M. U. ; Yetisen, A. K. ; Butt, H. Laser-Induced Surface Modification of Contact Lenses. Advanced Engineering Materials. DOI: 10.1002/adem.20170096 2018. Publisher's VersionAbstract
The authors report on the laser-induced modification of surface properties of contact lenses. Selective areas of the surface of commercial silicon-hydrogel contact lenses are patterned in array formats using different powers of the CO2 laser. 1D arrays of different groove densities, channels, and 2D intersecting architecture are fabricated. Contact angle measurements are carried out to measure the surface hydrophilicity, and extent of hydration is linked with the surface profile properties and the space gap between the fabricated patterns, which are controlled by the beam exposure time, beam power, and scan speed. Laser treatment of contact lenses results in improved hydration proportional to the density of laser ablated segments on the surface. The hydration time of water droplets on different lens surfaces is also recorded – all 2D patterned lenses show faster hydration as water quickly diffused into the bulk of the lens due to the extended interfacial area between the contact lens and the water droplet as a consequence of larger areal modification in 2D as compared with 1D patterns. The best wettability properties are obtained with 0.3 mm space gap, 9 W power, and 200 mm s−1 scan speed. Optical microscopy is used to image the 3D surface profiles of the modified lenses and the depth of the patterns and is correlated with the experimental observations. The maximum depth of 40 µm is observed with 0.3 mm space gap, 9 W, and 200 mm s−1 scan speed. Optical transmittance of broadband white light is measured to assess the surface treatment effects on the contact lenses. A large exposure and dense patterning of contact lens result in decreased (down to a minimum of 45%) in the light transmittance, which dictates the practical usability of such patterning. Surface treatment of contact lenses can be utilized to deposit stable conducting connection for on-lens-LEDs, displays, and communication antennas as well as for stabilizing biosensing materials and drug dispensing applications.
Yetisen, A. K. Biohacking. Trends in Biotechnology 2018. Publisher's VersionAbstract
Biohacking is a do-it-yourself citizen science merging body modification with technology. The motivations of biohackers include cybernetic exploration, personal data acquisition, and advocating for privacy rights and open-source medicine. The emergence of a biohacking community has influenced discussions of cultural values, medical ethics, safety, and consent in transhumanist technology.
Yi, J. ; Li, B. ; Yetisen, A. K. ; Yan, Q. ; Qiu, T. ; Iyer, K. S. ; Dai, H. ; Li, S. ; Jiang, N. Painful Terminal Neuroma Prevention by Capping PRGD/PDLLA Conduit in Rat Sciatic Nerves. Advanced Science. DOI: 10.1002/advs.201700876 2018. Publisher's Version
Khalid, M. W. ; Ahmed, R. ; Yetisen, A. K. ; Butt, H. Flexible Polymeric Dynamic Corner Cube Retroreflector Array for Temperature and Strain Sensing. RSC Advances 2018, 8 7588-7598. Publisher's VersionAbstract
Optical sensors for detecting temperature and strain play a crucial role in the analysis of environmental conditions and real-time remote sensing. However, the development of a single optical device that can sense temperature and strain simultaneously remains a challenge. Here, a flexible corner cube retroreflector (CCR) array based on passive dual optical sensing (temperature and strain) is demonstrated. A mechanical embossing process was utilised to replicate a three-dimensional (3D) CCR array in a soft flexible polymer film. The fabricated flexible CCR array samples were experimentally characterised through reflection measurements followed by computational modelling. As fabricated samples were illuminated with a monochromatic laser beam (635, 532, and 450 nm), a triangular shape reflection was obtained at the far-field. The fabricated flexible CCR array samples tuned retroreflected light based on external stimuli (temperature and strain as an applied force). For strain and temperature sensing, an applied force and temperature, in the form of weight suspension, and heat flow was applied to alter the replicated CCR surface structure, which in turn changed its optical response. Directional reflection from the heated flexible CCR array surface was also measured with tilt angle variation (max. up to 10°). Soft polymer CCRs may have potential in remote sensing applications, including measuring the temperature in space and in nuclear power stations.
Jiang, N. ; Yin, Y. X. ; Y. Wang, ; Li, B. B. ; Qiu, T. ; van Rijn, P. ; Yetisen, A. K. ; Tian, G. ; Yan, Q. J. ; Yi, J. L. ; et al. bFGF and Poly-RGD Cooperatively Establish Biointerface for Stem Cell Adhesion, Proliferation and Differentiation. Advanced Materials Interfaces. DOI: 10.1002/admi.201700702 2018. Publisher's VersionAbstract
Biointerface design is widely used to functionalize biomaterials with controllable physicochemical properties. Functionalized biointerface provides a versatile platform to connect biological entities and nonbiogenic materials. Existing nanofabrication approaches to create such a nanostructured biointerface involve in low stability of the functionalized nanolayer and simple functionalities that limit its applicability. Here, a stable nanolayered synthetic polypeptide (poly[LA-co-(Glc-alt-Lys)] and modified with arginine-glycine-aspartic acid, PRGD)/basic fibroblast growth factor (bFGF) biointerface is created via structural matching, charge interaction, and hydrogen bonding. The cooperative effect of the PRGD/bFGF biointerface shows multiple functionalities in promoting stem cell adhesion by 33% increase in cell adhesion to poly(d,l-lactic acid) substrate as compared to experiments on bare substrate as a control. Moreover, the biointerface enhances proliferation by 40% in cell density, potential differentiation by 62%, and gene expression by 40 and 80% respectively as compared to the control samples. The fabricated biointerface may have applications in nerve regeneration, tissue repair, and stem cell-based therapy.
Hassaan, M. U. ; Liu, Y. C. ; Yetisen, A. K. ; Butt, H. ; Friend, R. H. Energy Landscape of Vertically Anisotropic Polymer Blend Films toward Highly Efficient Polymer Light-Emitting Diodes (PLEDs). Advanced Functional Materials, DOI: 10.1002/adfm.201705903 (2018) 2018. Publisher's VersionAbstract
A blend of two hole-dominant polymers is created and used as the light emissive layer in light-emitting diodes to achieve high luminous efficiency up to 22 cd A−1. The polymer blend F81−xSYxis based on poly(9,9-dioctylfluorene) (F8) and poly(para-phenylene vinylene) derivative superyellow (SY). The blend system exhibits a preferential vertical concentration distribution. The resulting energy landscape modifies the overall charge transport behavior of the blend emissive layer. The large difference between the highest unoccupied molecular orbital levels of F8 (5.8 eV) and SY (5.3 eV) introduces hole traps at SY sites within the F8 polymer matrix. This slows down the hole mobility and facilitates a balance between the transport behavior of both the charge carriers. The balance due to such energy landscape facilitates efficient formation of excitons within the emission zone well away from the cathode and minimizes the surface quenching effects. By bringing the light-emission zone in the middle of the F81−xSYx film, the bulk of the film is exploited for the light emission. Due to the charge trapping nature of SY molecules in F8 matrix and pushing the emission zone in the center, the radiative recombination rate also increases, resulting in excellent device performance.
Jiang, N. ; Ahmed, R. ; Rifat, A. A. ; Guo, J. ; Yin, Y. X. ; Butt, H., Y. A. K. Functionalized Flexible Soft Polymer Optical Fibers for Laser Photomedicine. Advanced Optical Materials 2018, 6. Publisher's VersionAbstract
Optical waveguides allow propagating light through biological tissue in optogenetics and photomedicine applications. However, achieving efficient light delivery to deep tissues for long-term implantation has been limited with solid-state optical fibers. Here, a method is created to rapidly fabricate flexible, functionalized soft polymer optical fibers (SPOFs) coupled with silica fibers. A step-index core/cladded poly(acrylamide-co-poly(ethylene glycol) diacrylate)/Ca alginate SPOF is fabricated through free-radical polymerization in a mold. The SPOF is integrated with a solid-state silica fiber coupler for efficient light delivery. The cladded SPOF shows ≈1.5-fold increase in light propagation compared to the noncladded fiber. The optical loss of the SPOF is measured as 0.6 dB cm−1 at the bending angle of 70° and 0.28 dB cm−1 through a phantom tissue. The SPOF (inner Ø = 200 µm) integrated with a 21 gauge needle (inner Ø = 514 µm) is inserted within a porcine tissue. The intensity of light decreases ≈60%, as the SPOF is implanted as deep as 2 cm. Doped with fluorescent dye and gold nanoparticles, the SPOF fiber exhibits yellow-red and red illumination. Living cells can also be incorporated within the SPOF with viability. The flexible SPOFs may have applications in photodynamic light therapy, optical biosensors, and photomedicine.
Jiang, N. ; Montelongo, Y. ; Butt, H. ; Yetisen, A. K. Microfluidic Contact Lenses. Small. DOI: 10.1002/smll.201704363 2018. Publisher's VersionAbstract
Contact lens is a ubiquitous technology used for vision correction and cosmetics. Sensing in contact lenses has emerged as a potential platform for minimally invasive point-of-care diagnostics. Here, a microlithography method is developed to fabricate microconcavities and microchannels in a hydrogel-based contact lens via a combination of laser patterning and embedded templating. Optical microlithography parameters influencing the formation of microconcavities including ablation power (4.3 W) and beam speed (50 mm s−1) are optimized to control the microconcavity depth (100 µm) and diameter (1.5 mm). The fiber templating method allows the production of microchannels having a diameter range of 100–150 µm. Leak-proof microchannel and microconcavity connections in contact lenses are validated through flow testing of artificial tear containing fluorescent microbeads (Ø = 1–2 µm). The microconcavities of contact lenses are functionalized with multiplexed fluorophores (2 µL) to demonstrate optical excitation and emission capability within the visible spectrum. The fabricated microfluidic contact lenses may have applications in ophthalmic monitoring of metabolic disorders at point-of-care settings and controlled drug release for therapeutics.
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Zhang, Z. ; Dou, Q. ; Gao, H. ; Bai, B. ; Zhang, Y. ; Hu, D. ; A.K., Y. ; Butt, H. ; Yang, X. ; Li, C. ; et al. 30 s Response Time of K+ Ion-Selective Hydrogels Functionalized with 18-Crown-6 Ether Based on QCM Sensor. Advanced Healthcare Materials. DOI: 10.1002/adhm.201700873 2018. Publisher's VersionAbstract
Potassium detection is critical in monitoring imbalances in electrolytes and physiological status. The development of rapid and robust potassium sensors is desirable in clinical chemistry and point-of-care applications. In this study, composite supramolecular hydrogels are investigated: polyethylene glycol methacrylate and acrylamide copolymer (P(PEGMA-co-AM)) are functionalized with 18-crown-6 ether by employing surface initiated polymerization. Real-time potassium ion monitoring is realized by combining these compounds with quartz crystal microbalance. The device demonstrates a rapid response time of ≈30 s and a concentration detection range from 0.5 to 7.0 × 10−3 m. These hydrogels also exhibit high reusability and K+ ion selectivity relative to other cations in biofluids such as Na+, NH4+, Mg2+, and Ca2+. These results provide a new approach for sensing alkali metal ions using P(PEGMA-co-AM) hydrogels.
Kim, H. ; Beack, S. ; Han, S. ; Shin, M. ; Lee, T. ; Park, Y. ; Kim, K. S. ; Yetisen, A. K. ; Yun, S. H. ; Kwon, W. ; et al. Multifunctional Photonic Nanomaterials for Diagnostic, Therapeutic, and Theranostic Applications. Advanced Materials. DOI: 10.1002/adma.201701460 2018. Publisher's VersionAbstract
The last decade has seen dramatic progress in the principle, design, and fabrication of photonic nanomaterials with various optical properties and functionalities. Light-emitting and light-responsive nanomaterials, such as semiconductor quantum dots, plasmonic metal nanoparticles, organic carbon, and polymeric nanomaterials, offer promising approaches to low-cost and effective diagnostic, therapeutic, and theranostic applications. Reasonable endeavors have begun to translate some of the promising photonic nanomaterials to the clinic. Here, current research on the state-of-the-art and emerging photonic nanomaterials for diverse biomedical applications is reviewed, and the remaining challenges and future perspectives are discussed.

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