Printed Dual Cell Arrays for Multiplexed Sensing - ACS Biomaterials

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Printed Dual Cell-Silk Arrays for Multiplexed Sensing Irina Drachuk, Rattanon Suntivich, Rossella Calabrese, Svetlana Harbaugh, Nancy Kelley-Loughnane, David L Kaplan, Morley Stone, and Vladimir V. Tsukruk ACS Biomater. Sci. Eng., Just Accepted Manuscript • DOI: 10.1021/ab500085k • Publication Date (Web): 01 Apr 2015 Downloaded from http://pubs.acs.org on April 9, 2015

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ACS Biomaterials Science & Engineering

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Printed Dual Cell Arrays for Multiplexed Sensing

By Irina Drachuk†, Rattanon Suntivich†, Rossella Calabrese‡, Svetlana Harbaughʃ, Nancy Kelley-Loughnaneʃ, David L. Kaplan‡, Morley Stoneʃ, Vladimir V. Tsukruk†*

†

School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (USA) ‡

Department of Biomedical Engineering, Tufts University, Medford, MA 02155 (USA)

ʃ

Air Force Research Laboratory, Directorate of Human Effectiveness, Wright-Patterson AFB, Dayton, OH 45433 (USA)

[*] Prof. V. V. Tsukruk School of Materials Science and Engineering, Georgia Institute of Technology Atlanta, Georgia 30332-0245 (USA); E-mail: [email protected]

Keywords: inkjet printing, silk fibroin, cell encapsulation, dual cell arrays, thin film biosensors

ACS Paragon Plus Environment


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Abstract We demonstrated inkjet printing of large-scale dual-type encapsulated bacterial cell arrays for prospective multiplexing sensing.

The dual cell arrays were constructed

based on two types of bioengineered E. coli cells hosting fluorescent reporters (greenGFPa1 and red-turboRFP) capable to detect different target chemicals. The versatility of inkjet printing allows for the fabrication of uniform multilayered confined structures composed of silk ionomers that served as nests for in-printing different cells. Furthermore, sequential encapsulation of “red” and “green” cells in microscopic silk nest arrays with the preservation of their function allowed for facile confinement of cells into microscopic silk nests, where cells retained dual red-green response to mixed analyte environment.

Whole-cell dual arrays immobilized in microscopic biocompatible silk

matrices were readily activated after prolonged storage (up to 3 months, ambient conditions), showing red-green pattern and demonstrating an effective prototype of robust and long-living multiplexed biosensors for field applications.


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Introduction Biosensing materials based on both eukaryotic and prokaryotic systems are envisaged for screening and robust identification of chemical and biological toxins or biomarkers to monitor the type of biological activity involved.1,2,3,4,5 Data on the effects of the tested compound on gene expression, metabolic activity, cell viability, bioavailability and genotoxicity can be sensed and reported by live cells.6,7,8 Various biochips based on living mammalian cell systems are more sensitive to environmental perturbations and can mimic human cellular responses, however, require extra care to maintain cells health in order to keep them genetically intact and alive. Microbial cells, on the other hand, offer many advantages over mammalian cells for practical applications. They are readily obtainable, easy to grow and maintain, can be genetically tailored to emit the desired signal in the presence of the specific target compound (analyte) or environmental conditions to cover the broad range of toxic elements and can be exploited for facile printing into biosensor arrays.9

Indeed, the fabrication of single-strain cell arrays immobilized onto biocompatible substrates has already been demonstrated by using microcontact printing, soft lithography and inkjet printing technology.10,11,12,13,14 Originating from the simple printing of robust microbial cells, the concept of delivering viable cells to specific locations has been extended to more sensitive mammalian cells that retained viability and functions throughout the printing processes.15,16,17,18,19 Later, envisioned by the ability of printers to carry multiple bioink cartridges, the simplified early versions of living tissue analogs



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were constructed for drug and chemical screening, toxicological evaluations, regenerative medicine, and basic cell biology. 20,21,22,23,24,25

To date, various synthetic and bio-inks, such as natural and synthetic protein solutions combined with living cells have been tested to form cells-bearing scaffolds or films.26,27,28,29,30,31,32 The next step is the construction of whole-cell multiplex arrays, where cells originally transfected with different target-specific reporter genes would be embedded into a biocompatible matrix to preserve their long-term function. Progress has been recently demonstrated with E. coli cells transferred with two variations of green fluorescent plasmid (GFP), uvGFP and eGFP plasmids.

Even though

microarrays were constructed by depositing cells mixed with soft silica-glycerol matrix via contact pin-printing technique, the bulk of sol-gel-derived silica material required storage in aqueous environment to prevent excessive drying and cracking.33

The criteria for biocompatibility, mechanical strength and permeability of cell-containing matrix are essential for the proper function of cell-based sensors in order to correctly identify the molecules of interest in a timely manner. Therefore, the objectives for this study were to construct true dual-color (with distinct excitation and emission peaks) cell microarrays immobilized in biocompatible matrix that satisfies several criteria. Easily reproducible and mechanically robust thin microscopic 3D substrates must be able to preserve cellular activity after drying, allowing the storage and transfer of cells for prolong period of time in desiccated state while providing fast diffusion of nutrients and analyte molecules for quick recognition and activation of cells.


The complexity of

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precise delivery of cells in predesigned microarray matrix makes the multi-cartridge inkjet printing to be the ideal platform for construction of several cell lines arrays, which has not been thoroughly explored to date.

Here, we demonstrate the feasibility of piezoelectric inkjet printing to fabricate largescale, thin (~1.1±0.1 µm) and robust microarrays from silk materials hosting two different strains of E. coli cells that harbor different fluorescent reporter genes (green GFPa1 and red - turboRFP).

Recombinant cells were sandwiched between

multilayered silk mats that served as cytocompatible nests and held cells secure during printing-in and incubation in cell medium. Alternating encapsulation of “red” and “green” cells in hydrogel silk arrays allowed for facile confinement of cells into microscopic arrays with the preservation of their ability to grow and function. Cytocompatible silk hydrogel mats facilitated long-term cells storage and did not interfere with cells’ selective reaction to mixed target analytes thus demonstrating both green and red response colors. The dual-color cell-silk arrays constructed here represent a prototype of multiplexing cell-based sensors with dual functionality, which were robust and capable of retaining functionality after long-term storage under ambient conditions.

Experimental Section Materials. Mono-basic sodium phosphate, theophylline, amino acids, ampicillin sodium salt, isopropyl β-D-1-thiogalactopyranoside (IPTG) were purchased from Sigma-Aldrich. Luria-Bertani (Difco) powder was purchased from BD (Franklin Lakes, NJ). Polystyrene (PS, Mw = 250 000 Da) and toluene (J. T. Baker grade®) were purchased from VWR



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(Radnor, PA). Nanopure (Barnstead Nanopure system) water with a resistivity of 18.2 MΩcm was used in all experiments. Silk fibroin (SF) was extracted from Bombyx mori cocoons according to established procedures.34

Poly(amino acid)-modified silk

materials were obtained according to previously published methods that involve diazonium activation of the abundant tyrosine side chains in SF chains, followed by chemical conjugation of poly(L-lysine) or poly(L-glutamic acid) to produce silk fibroinpoly(L-lysine) (SF-PLL) and silk fibroin-poly(glutamic acid) (SF-PGA) ionomers.35 Glass substrates (from VWR) were cleaned with piranha solution according to the established protocol.36 Thin film of PS (2% w/v in toluene) was spin-coated at 3,000 rpm in order to increase hydrophobicity of the glass substrates for high quality multilayered structures.

E. coli cells. BL21 E. coli cells (Invitrogen, Carlsbad, CA) were used in this study. Bacterial cells were transformed with plasmid harboring a riboswitch construct where theophylline synthetic riboswitch (clone 12.1) was placed upstream of the sequence encoding a new fluorescent protein (GFPa1) from Amphioxus within pSAL vector (pSAL:RS12.1GFPa1His).37,38

BL21 E. coli cells harboring a multicopy plasmid

pET21a:turboRFPHis were also used to prepare dual arrays. Construction of pET21:turboRFPHis was performed in DH5α E. coli cells (Invitrogen, Carlsbad, CA). The coding sequence of turboRFP was amplified from plasmid pUC57:turboRFP.

The sequence of the construct has been verified by DNA sequencing at the PlantMicrobe Genomic Facility of The Ohio State University. Growth of cells has been performed in cell incubator (Brunswick) at 37 °C in Luria-Bertani (LB) broth containing


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100 mg/L ampicillin during vigorous shaking (225 rpm). Cells have been harvested at early stage of exponential growth (0.3-0.4 a. u. based on 0-2 scale). For activation of cellular riboswitch (RS), synthetic cell medium containing reduced concentration of amino acids was used supplemented with theophylline (100 mM stock solution, 0.05 M NaH2PO4 buffer, pH 5.5), which was diluted into assay to the final concentration of 2.5 mM and 5 mM. Activation of turboRFP protein was performed with isopropyl β-D-1thiogalactopyranoside (IPTG, 100 mM aqueous stock solution) diluted to the final concentrations of 0.5 mM and 1 mM.

Printing of cell-based biosensor arrays.

A JetLab II inkjet printer (MicroFab

Technologies) capable of holding four cartridges with 50 µm nozzle size was used for all materials. The inkjet printing platform allowed for rapid and easy printing of two silk ionomer derivatives: SF-PLL and SF-PGA, and Gram-negative bacteria (E. coli) expressing two reporter signals, (green fluorescent protein, GFPa1) and red fluorescent protein (turboRFP), respectively (Scheme 1). For printing, cells were collected in 15 mL tubes by centrifugation at 3,000 rpm for 2 min, washed three times and kept in phosphate buffer (0.05 M NaH2PO4, 0.1 M KH2PO4, pH 5.5). Silk ionomers (1 mg/mL in NaH2PO4 buffer, pH 5.5) were printed on PS coated glass substrates in alternate fashion starting from SF-PLL followed by SF-PGA constituting 1 bilayer structure until desired number of silk bilayers was achieved.

In order to create biosensor arrays

(20x20, and dual type 2x6), E. coli cell suspension was ejected on the top of 3 bilayer silk structure followed by sealing cells with another 3 bilayer structure of silk ((SFPLL/SF-PGA)3‒E.coli‒(SF-PLL/SF-PGA)3 sandwich structure). Cell arrays were printed



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as circular dots of 100 µm size and spaced 150 µm apart. Even though after printing cell envelopes can be partially compromised, the bacteria retained full activity during short-term storage (3 days, 4 °C, ambient conditions) and long-term storage (for up to three months at 4 °C, ambient conditions) and were readily actuated within less than an hour after warming.

Confocal Laser Scanning Microscopy (CLSM). Confocal imaging was performed on Zeiss confocal laser scanning module (Zeiss LSM 510, Germany) using the following objectives EC Plan-Neofluar 10x (NA 0.3), Plan-Apochromat 20x (NA 0.8) or LD PlanNeofluar 40x (NA 0.6). Imaging of GFPa1 and turboRFP fluorescence was performed using Ar (λex=488 nm) and He-Ne (λex=543 nm) lasers with LP 505 nm and LP 560 nm band-pass filters for GFP-bearing and turboRFP-bearing cells, respectively.

Atomic Force Microscopy (AFM). The topographical images of air-dried samples were collected on a Dimension-3000 AFM (Digital Instruments) according to the established procedure in light tapping mode using silicon V-shape cantilevers (spring constant 46 N/m).39

Results and Discussion Silk template and cell printing.

Proper ultrathin cytocompatible array templates are

critical for successful cell printing on solid substrates. Therefore, layer-by-layer (LbL) inkjet printing was employed to first print several bilayers of silk ionomer dots as a cushioning matrix to host cells, followed by injection of recombinant bacterial cells and


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finally, sealing the cells with the same number of silk ionomer bilayers to construct sandwich structures (Scheme 1).40 Sequential LbL printing of hydrophilic solutions on hydrophobic substrates allowed for the optimization of the size and shape of printed structures with capability to fabricate the complex structure arrays of pre-programmed thickness.41,42,43

Moreover, the requirement for having robust and biocompatible

substrates was necessitated by the natural ability of bacteria to be washed away by the medium flow if cells were not strongly immobilized to the substrate.

The

cytocompatibility of silk material with cells has been demonstrated in our recent studies revealing functional microbial cells after encapsulation into silk LbL shells.44,45

Stable silk dot structures were constructed by sequential LbL injection of positivelycharged silk ionomer solution (SF-PLL) followed by negatively-charged silk ionomer solution (SF-PGA) comprising one bilayer structure (SF-PLL/SF-PGA)1. The versatility of inkjet printer allowed constructing large scale 20 x 20 arrays of multilayered circular silk substrates with elevated rims caused by coffee-ring effect, the structure ideal for injection and hosting cells.40 Moreover, owing to strong ionic interactions between two types of silk polyelectrolyte components, 35,45 the silk structures demonstrated excellent shape stability even after incubation in cell medium for more than 24 hours (Figure 1A). Multilayered structures of silk ionomers with optimal solution concentrations were printed on two types of transparent hydrophobic substrates: hard (glass with ~2 µm polystyrene coating), and flexible (polyethylene terephthalate) without washing steps between the injection steps. The average diameter of the printed dots was about 100



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µm under given conditions, and these features sizes can be controlled by the concentration of the injectable solutions and the hydrophobicity of the substrate.43

Multilayered ((SF-PLL/SF-PGA)5) silk dots were optically transparent (Figure 1A). By injecting cells suspension of high concentration (>5×108 cells/mL), uniform coverage of a high density of cells was achieved throughout the surface of the silk pad that reduced the transparency of the silk arrays (Figure 1B). Reconstructed 3D AFM images of a typical (SF-PLL/SF-PGA)5 silk dot revealed the concave profile of a circular shaped dot about 100 µm in size with a depression in the center (600 ± 100 nm) and elevated edges (1,000 ± 130 nm), useful as a nest structure for depositing and holding the cells as discussed in detail elsewhere (Figure 2A).40,41

After injection and sealing the cells

with additional layers of silk ionomers, the profile of the sandwich structure remained unchanged (Figure 1C), however the roughness increased significantly from 9 ± 2 nm up to 230 ± 70 nm (Figure 2B).

The thickness of the (SF-PLL/SF-PGA)1–E.coli‒(SF-PLL/SF-PGA)1 sandwich structure was 780 ± 110 nm as measured directly after the printing and before incubation in the cell medium. By increasing the number of printed bilayers beneath and above of the cells, the thickness of the sandwich structures increased accordingly to 1120 ± 120 nm (for (SF-PLL/SF-PGA)3‒E.coli‒(SF-PLL/SF-PGA)3 structure) (Figure 2B). Interestingly, the surface roughness remained on the same scale (230 ± 60 nm), suggesting that the morphology coarseness of the sandwich structures was defined mainly by the presence of the cells (Figures 2C, 3). AFM imaging also confirmed uneven seeding of bacterial


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cells throughout the surface of the initial silk pad. While in the center of the pad the density of cells was ~5 cells/µm2, the coverage of cells occupying the rims was ~25 cells/µm2 (Figures 2C, 3). The higher coverage of cells around the rims of the silk pad was associated with the coffee-ring effect coupled with the initial concave profile of the silk pad when cells were dragging towards higher edges of the pad during evaporation.40

The stability of (SF-PLL/SF-PGA)3‒E.coli‒(SF-PLL/SF-PGA)3 sandwich structures was assessed by incubation in synthetic minimal cell medium (SMM) at 37 ˚C during mild agitation (100 rpm) (Figures 3, 4). With respect to the shape of multilayered sandwich stacks, the size of circular dots remained unchanged. However, the thickness of the stacks changed significantly. Specifically, initial decrease in thickness from 1124 ± 120 nm to 540 ± 30 nm (50% volume change) was observed after 30 min, which was stabilized thereafter (Figure 4). Following the incubation for extended period of time (18 hours), the silk-cells-silk sandwich structures increased in height by ~ 25%, which is usually associated with water uptake occurring in hydrogel-like material. The initial drop in thickness was associated with release of unbound protein molecules from the multilayered stacks as the result of elimination of intermediate rinsing steps. At the same time, the cell density was not affected by the removal of excess of silk component, or swelling of the silk hydrogel multilayers during prolonged exposure to the cell medium, as it appeared that the number of cells had not significantly changed (Figure 3B-C).

Apparently, printed-in cells behaved as bridges anchoring the

macromolecules and hence providing extra stability to multilayer structures.



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Stochiometrically-equal in charged groups, silk ionomers were assembled through strong cooperative electrostatic interactions as the pH of the ionomer solutions was set apart from the isoelectric points so that proteins were sufficiently charged under the experimental conditions. Moreover, ionically-paired multilayered silk protein stacks behaved as hydrogel networks, increasing in thickness and demonstrating swelling up to 30% after incubation in cell medium for more than 18 hours. Limited intermixing of silk protein derivatives during inkjet-assisted LbL assembly occurred as the result of fast radial solvent evaporation and small volume solvent casting, yielding the formation of complex structures of loops and folds in addition to crystalline portions of silk proteins that usually form upon drying.46

After removal of unbound macromolecules that

provided free volume for swelling during longer incubation (Figures 3, 4), the resulting protein network was stable in low-ionic strength media due to cooperative interactions of the loops and entanglements between layered protein macromolecules.

Printing “green” cell arrays. The ability of the cells to function after short-term (3 days, 4 ˚C) and long-term storage (3 months, 4 ˚C) was assessed in order to assure the biocompatibility of silk-based matrix to retain the cells, support their activity and promote effective diffusion of small molecules (target analytes) through protective multilayers. The ability of the encapsulated cells to respond to a specific analyte is based on the engineered genetic modular signaling and sensing circuits, named riboswitch, a cellular construct composed of the aptamer and expression platform domain. Bacterial cells exploited in our study were transformed with theophylline synthetic riboswitch, which


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was coupled with GFPa1 reporter protein gene.38 This cellular based sensor system was demonstrated to be robust and effective in recognizing analyte even after E. coli cells have been subjected to shear forces and hard landing onto the silk substrates.

Figure 5 represents time-resolved activation of the cellular riboswitch with consecutive appearance of GFP fluorescence in the presence of the analyte. Specifically, after short-term storage (3 days at 4oC), cells retained their cellular function and amplified production of GFP within the first hours after exposure to theophylline. Furthermore, long-term storage of cells embedded in silk structures demonstrated full capability of cells to function (Figure 5A). After storage for up to 3 months (ambient conditions), cells were easily revived and demonstrated detectable level of GFP signal within 1 hour and a maximum intensity of GFP fluorescence after 2 hours of exposure to target analyte (Figure 5A-B). It is important to note that activated cells were confined within templated silk dot regions and were not widely spread across the whole surface area, as was observed for the cell samples without pre-printed silk templates (not shown). Moreover, when left in the cell medium for prolonged period of time (24 hours), the silk matrix became progressively swelled, and promoted active proliferation of cells, as demonstrated by increased number of cells, and subsequently, increased fluorescence signal generated by cells collectively (Figure 5C).

Dual “red”-“green” cell arrays. Finally, dual arrays of cells with two reporter elements (turboRFP - “red” and GFPa1 – “green”) capable of detecting specific analyte were constructed by immobilizing E. coli cells in silk multilayered structures as 2 x 6 “green”



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dot arrays adjacent to 2 x 6 “red” dot arrays. Figure 6 represents confocal images of fluorescent cell arrays as the result of specific recognition of theophylline (riboswitch coupled with GFPa1) (“green” cells) and IPTG (IPTG inducible protein, turboRFP) (“red” cells) after exposure to mixed analyte compounds. We observed that while incubated in the mixture of both targeted molecules, cells were quickly activated and produced fluorescent signals specific to each analyte present in the solution.

The variation of fluorescence intensity demonstrated that theophylline-sensitive “green” cells reached the highest intensity within the first two hours of incubation in the mixture broth, while IPTG-sensitive “red” cells - only within one hour (Figure 7). Time-delayed shift in the fluorescence peaks was due to the differences in genetic expression profiles in two types of cells in addition to the distinct fluorescent properties for GFPa1 and turboRFP proteins.

While “green” cells have been transfected with a riboswitch

construct where the promoter was coupled with a fluorescent protein gene, the “red” cells have had only a fluorescent plasmid.

Hence, complex activation of GFPa1

reporter signal in “green” cells was postponed by an extra hour. Additionally, timedelayed correlation of the fluorescence maxima with low concentration of analytes was also observed suggesting slower intracellular transport kinetics with low concentration gradients (Figures 7).

Conclusions In conclusion, a prototype version of multiplexing cell-based biosensor arrays was demonstrated where recombinant cells were printed between silk templated arrays


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using piezoelectric inkjet technology.

Transgenic bacterial cells with two reporter

elements (GFPa1 and turboRFP) were capable of rapid detection of specific analyte in the mixed solution. Biochips fabricated from transgenic bacterial cells and immobilized in silk hydrogels represent effective and robust platforms for field applications as longterm function of cells was not affected.

Silk-based matrix demonstrated to be an

effective platform for holding, protecting, storing and keeping cells ready for immediate activation.

Presented whole-cell dual-color colorimetric arrays demonstrated a

possibility to construct multiplexing biosensors for real-time detection of multiple target analytes, which have a potential for high-throughput chemical and pharmaceutical screening, environmental monitoring, and food safety. Fast identification of analytes can be specifically beneficial for field applications where quick detection combined with prolonged shelf-life is highly required.

Acknowledgments: The study was supported by Grants FA9550-14-1-0269 and FA9550-09-1-0162 (BIONIC Center) from Air Force Oﬃce of Scientiﬁc Research and National Science Foundation CBET-1402712. We are grateful to Dr. M. Chyasnavichyus for the help with digital image formatting and Dr. R. Saldanha (AFRL) for plasmid pUC57:turboRFP.



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SF-PLL SF-PGA E. coli cells with different reporters

Fluorescent signal

Mixture of analytes

Scheme 1. Schematics of ink-jet printing routine for dual-color cell-cell arrays.


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A

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Figure 1. Optical images of (SF-PLL/SF-PGA)5 silk array dots (A) and (SF-PLL/SF-PGA)3E.coli-(SF-PLL/SF-PGA)3 cell arrays (B). Rendered confocal fluorescent image of a typical sandwich structure dot with bacterial cells injected between (SF-PLL/SF-PGA)6 multilayers, (SF-PLL/SF-PGA)3−E.coli−(SF-PLL/SF-PGA)3 structure (C).



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A

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Figure 2. 3D AFM images of silk nest before (A) and after (B) cell deposition: (SF-PLL/SFPGA)5 dot (A) and (SF-PLL/SF-PGA)3−E.coli−(SF-PLL/SF-PGA)3 sandwich structure (B); AFM topographical images of (SF-PLL/SF-PGA)1−E.coli−(SF-PLL/SF-PGA)1 sandwich structure at different magnifications (C).


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Figure 3. Topographical AFM images of (SF-PLL/SF-PGA)3−E.coli−(SF-PLL/SF-PGA)3 sandwich structure after incubation in SMM medium for 0 min (control) (column A), 30 min (column B) and 18 hours (column C) at two different magnifications (z-scale = 2 µm).



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1400 1200

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Figure 4. Thickness of (SF-PLL/SF-PGA)3−E.coli−(SF-PLL/SF-PGA)3 sandwich structure during incubation in SMM medium at different time periods. Data shown are the average ± standard deviation (n=3).


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Figure 5. E. coli cells with activated riboswitch (theophylline, 5 mM) after long-term storage (A, B) and short-term storage (C). Cells have been encapsulated in (SF-PLL/SFPGA)3−E.coli−(SF-PLL/SF-PGA)3 nests. Capturing of individual silk-cell-silk dot has been performed after 1 hour, 2 hours, and 3 hours of culturing for long-term storage (columns in A) and after 29 hours for short-term storage (row C). Large scale fluorescent and bright field (BF) view of activated (SF-PLL/SF-PGA)3−E.coli−(SF-PLL/SF-PGA)3 cell arrays after incubation in cell medium for 3 hours (B).



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turboRFP

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100 µm

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Figure 6. Confocal fluorescent images of dual 2 x 6 cell arrays representing complex activation of specific fluorescence (GFPa1 in “green” cells and turboRFP in “red” cells) after exposure to mixed analytes solution and incubation for different time periods (A). Two types of E. coli cells were sandwiched between (SF-PLL/SF-PGA)6 silk multilayer stacks.


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Figure 7. Kinetics of fluorescence intensity in E. coli cells expressing GFPa1 (green) and turboRFP (red) plasmids with respect to analyte concentration (theophylline, (top) and IPTG (bottom)). Data shown are the average ± standard deviation (n=15).



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For Table of Contents Use Only

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Ink-jet dual cells

TOC

Printed Dual Cell Arrays for Multiplexed Sensing Irina Drachuk, Rattanon Suntivich, Rossella Calabrese, Svetlana Harbaugh, Nancy Kelley-Loughnane, David L. Kaplan, Morley Stone, Vladimir V. Tsukruk

We demonstrated the feasibility of inkjet printing of large-scale dual silk-encapsulated cell arrays for prospective multiplexing sensing, which have been constructed based upon two types of bioengineered E. coli cells hosting fluorescent reporters (green – GFPa1 and red – turboRFP) capable to detect different target chemicals.


Printed Dual Cell Arrays for Multiplexed Sensing - ACS Biomaterials

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