Pink verrucous plaque in a man with systemic mastocytosis.

Porokeratosis ptychotropica is a rare and commonly misdiagnosed subtype of porokeratosis involving the body folds. We present a 53-year-old man with systemic mastocytosis who presented with a pruritic, verrucous plaque in the gluteal fold that showed multiple cornoid lamellae on histopathologic evaluation, diagnostic of porokeratosis ptychotropica. Various treatments have been reported, including topical corticosteroids, retinoids, vitamin D analogs, calcineurin inhibitors, imiquimod, phototherapy, cryotherapy, or ablative laser therapy, but recurrences are common.

Incorporating LsrK AI-2 quorum quenching capability in a functionalized biopolymer capsule.

Antibacterial resistance is an issue of increasing severity as current antibiotics are losing their effectiveness and fewer antibiotics are being developed. New methods for combating bacterial virulence are required. Modulating molecular communication among bacteria can alter phenotype, including attachment to epithelia, biofilm formation, and even toxin production. Intercepting and modulating communication networks provide a means to attenuate virulence without directly interacting with the bacteria of interest. In this work, we target communication mediated by the quorum sensing (QS) bacterial autoinducer-2, AI-2. We have assembled a capsule of biological polymers alginate and chitosan, attached an AI-2 processing kinase, LsrK, and provided substrate, ATP, for enzymatic alteration of AI-2 in culture fluids. Correspondingly, AI-2 mediated QS activity is diminished. All components of this system are "biofabricated"-they are biologically derived and their assembly is accomplished using biological means. Initially, component quantities and kinetics were tested as assembled in microtiter plates. Subsequently, the identical components and assembly means were used to create the "artificial cell" capsules. The functionalized capsules, when introduced into populations of bacteria, alter the dynamics of the AI-2 bacterial communication, attenuating QS activated phenotypes. We envision the assembly of these and other capsules or similar materials, as means to alter QS activity in a biologically compatible manner and in many environments, including in humans.

Constructing "quantized quorums" to guide emergent phenotypes through quorum quenching capsules.

Microbial cells have for many years been engineered to facilitate efficient production of biologics, chemicals, and other compounds. As the "metabolic" burden of synthetic genetic components can impair cell performance, microbial consortia are being developed to piece together specialized subpopulations that collectively produce desired products. Their use, however, has been limited by the inability to control their composition and function. One approach to leverage advantages of the division of labor within consortia is to link microbial subpopulations together through quorum sensing (QS) molecules. Previously, we directed the assembly of "quantized quorums," microbial subpopulations that are parsed through QS activation, by the exogenous addition of QS signal molecules to QS synthase mutants. In this work, we develop a more facile and general platform for creating "quantized quorums." Moreover, the methodology is not restricted to QS-mutant populations. We constructed quorum quenching capsules that partition QS-mediated phenotypes into discrete subpopulations. This compartmentalization guides QS subpopulations in a dose-dependent manner, parsing cell populations into activated or deactivated groups. The capsular "devices" consist of polyelectrolyte alginate-chitosan beads that encapsulate high-efficiency (HE) "controller cells" that, in turn, provide rapid uptake of the QS signal molecule AI-2 from culture fluids. In this methodology, instead of adding AI-2 to parse QS-mutants into subpopulations, we engineered cells to encapsulate them into compartments, and they serve to deplete AI-2 from wild-type populations. These encapsulated bacteria therefore, provide orthogonal control of population composition while allowing only minimal interaction with the product-producing cell population or consortia. We envision that compartmentalized control of QS should have applications in both metabolic engineering and human disease. Biotechnol. Bioeng. 2017;114: 407-415. © 2016 Wiley Periodicals, Inc.

Conferring biological activity to native spider silk: A biofunctionalized protein-based microfiber.

Spider silk is an extraordinary material with physical properties comparable to the best scaffolding/structural materials, and as a fiber it can be manipulated with ease into a variety of configurations. Our work here demonstrates that natural spider silk fibers can also be used to organize biological components on and in devices through rapid and simple means. Micron scale spider silk fibers (5-10 µm in diameter) were surface modified with a variety of biological entities engineered with pentaglutamine tags via microbial transglutaminase (mTG). Enzymes, enzyme pathways, antibodies, and fluorescent proteins were all assembled onto spider silk fibers using this biomolecular engineering/biofabrication process. Additionally, arrangement of biofunctionalized fiber should in of itself generate a secondary level of biomolecular organization. Toward this end, as proofs of principle, spatially defined arrangement of biofunctionalized spider silk fiber was shown to generate effects specific to silk position in two cases. In one instance, arrangement perpendicular to a flow produced selective head and neck carcinoma cell capture on silk with antibodies complexed to conjugated protein G. In a second scenario, asymmetric bacterial chemotaxis arose from asymmetric conjugation of enzymes to arranged silk. Overall, the biofabrication processes used here were rapid, required no complex chemistries, were biologically benign, and also the resulting engineered silk microfibers were flexible, readily manipulated and functionally active. Deployed here in microfluidic environments, biofunctional spider silk fiber provides a means to convey complex biological functions over a range of scales, further extending its potential as a biomaterial in biotechnological settings. Biotechnol. Bioeng. 2017;114: 83-95. © 2016 Wiley Periodicals, Inc.

Controlling localization of Escherichia coli populations using a two-part synthetic motility circuit: An accelerator and brake.

Probiotics, whether taken as capsules or consumed in foods, have been regarded as safe for human use by regulatory agencies. Being living cells, they serve as "tunable" factories for the synthesis of a vast array of beneficial molecules. The idea of reprogramming probiotics to act as controllable factories, producing potential therapeutic molecules under user-specified conditions, represents a new and powerful concept in drug synthesis and delivery. Probiotics that serve as drug delivery vehicles pose several challenges, one being targeting (as seen with nanoparticle approaches). Here, we employ synthetic biology to control swimming directionality in a process referred to as "pseudotaxis." Escherichia coli, absent the motility regulator cheZ, swim sporadically, missing the traditional "run" in the run:tumble swimming paradigm. Upon introduction of cheZ in trans and its signal-generated upregulation, engineered bacteria can be "programmed" to swim toward the source of the chemical cue. Here, engineered cells that encounter sufficient levels of the small signal molecule pyocyanin, produce an engineered CheZ and swim with programmed directionality. By incorporating a degradation tag at the C-terminus of CheZ, the cells stop running when they exit spaces containing pyocyanin. That is, the engineered CheZ modified with a C-terminal extension derived from the putative DNA-binding transcriptional regulator YbaQ (RREERAAKKVA) is consumed by the ClpXP protease machine at a rate sufficient to "brake" the cells when pyocyanin levels are too low. Through this process, we demonstrate that over time, these engineered E. coli accumulate in pyocyanin-rich locales. We suggest that such approaches may find utility in engineering probiotics so that their beneficial functions can be focused in areas of principal benefit.

Influences of Adhesion Variability on the "Living" Dynamics of Filamentous Bacteria in Microfluidic Channels.

Microfabricated devices have increasingly incorporated bacterial cells for microscale studies and exploiting cell-based functions in situ. However, the role of surface interactions in controlling the bacterial cell behavior is not well understood. In this study, microfluidic substrates of varied bacterial-binding affinity were used to probe the interaction-driven behavior of filamentous Escherichia coli. In particular, cell alignment under controlled shear flow as well as subsequent orientation and filamentation were compared between cells presenting distinct outer membrane phenotypes. We demonstrated that filaments retained position under flow, which allowed for dynamic single-cell monitoring with in situ elongation of over 100 µm for adherent cells. This maximum was not reached by planktonic cells and was, therefore, adhesion-dependent. The bound filaments initially aligned with flow under a range of flow rates and their continual elongation was traced in terms of length and growth path; analysis demonstrated that fimbriae-mediated adhesion increased growth rate, increased terminal length, as well as dramatically changed the adherent geometry, particularly buckling behavior. The effects to filament length and buckling were further exaggerated by the strongest, specificity-driven adhesion tested. Such surface-guided control of the elongation process may be valuable to yield interesting "living" filamentous structures in microdevices. In addition, this work may offer a biomedically relevant platform for further elucidation of filamentation as an immune-resistant morphology. Overall, this work should inspire broader exploration of microfabricated devices for the study and application of single bacterial cells.

Autonomous bacterial localization and gene expression based on nearby cell receptor density.

Escherichia coli were genetically modified to enable programmed motility, sensing, and actuation based on the density of features on nearby surfaces. Then, based on calculated feature density, these cells expressed marker proteins to indicate phenotypic response. Specifically, site-specific synthesis of bacterial quorum sensing autoinducer-2 (AI-2) is used to initiate and recruit motile cells. In our model system, we rewired E. coli's AI-2 signaling pathway to direct bacteria to a squamous cancer cell line of head and neck (SCCHN), where they initiate synthesis of a reporter (drug surrogate) based on a threshold density of epidermal growth factor receptor (EGFR). This represents a new type of controller for targeted drug delivery as actuation (synthesis and delivery) depends on a receptor density marking the diseased cell. The ability to survey local surfaces and initiate gene expression based on feature density represents a new area-based switch in synthetic biology that will find use beyond the proposed cancer model here.

Encapsulated fusion protein confers "sense and respond" activity to chitosan-alginate capsules to manipulate bacterial quorum sensing.

We demonstrate that "nanofactory"-loaded biopolymer capsules placed in the midst of a bacterial population can direct bacterial communication. Quorum sensing (QS) is a process by which bacteria communicate through small-molecules, such as autoinducer-2 (AI-2), leading to collective behaviors such as virulence and biofilm formation. In our approach, a "nanofactory" construct is created, which comprises an antibody complexed with a fusion protein that produces AI-2. These nanofactories are entrapped within capsules formed by electrostatic complexation of cationic (chitosan) and anionic (sodium alginate) biopolymers. The chitosan capsule shell is crosslinked by tripolyphosphate (TPP) to confer structural integrity. The capsule shell is impermeable to the encapsulated nanofactories, but freely permeable to small molecules. In turn, the capsules are able to take in substrates from the external medium via diffusion, and convert these via the nanofactories into AI-2, which then diffuses out. The exported AI-2 is shown to stimulate QS responses in vicinal Escherichia coli. Directing bacterial population behavior has potential applications in next-generation antimicrobial therapy and pathogen detection. We also envision such capsules to be akin to artificial "cells" that can participate in native biological signaling and communicate in real-time with the human microbiome. Through such interaction capabilities, these "cells" may sense the health of the microbiome, and direct its function in a desired, host-friendly manner.

High-Plex Spatial RNA Profiling Reveals Cell Type‒Specific Biomarker Expression during Melanoma Development.

Early diagnosis of melanoma is critical for improved survival. However, the biomarkers of early melanoma evolution and their origin within the tumor and its microenvironment, including the keratinocytes, are poorly defined. To address this, we used spatial transcript profiling that maintains the morphological tumor context to measure the expression of >1,000 RNAs in situ in patient-derived formalin-fixed, paraffin-embedded tissue sections in primary melanoma and melanocytic nevi. We profiled 134 regions of interest (each 200 µm in diameter) enriched in melanocytes, neighboring keratinocytes, or immune cells. This approach captured distinct expression patterns across cell types and tumor types during melanoma development. Unexpectedly, we discovered that S100A8 is expressed by keratinocytes within the tumor microenvironment during melanoma growth. Immunohistochemistry of 252 tumors showed prominent keratinocyte-derived S100A8 expression in melanoma but not in benign tumors and confirmed the same pattern for S100A8's binding partner S100A9, suggesting that injury to the epidermis may be an early and readily detectable indicator of melanoma development. Together, our results establish a framework for high-plex, spatial, and cell type‒specific resolution of gene expression in archival tissue applicable to the development of biomarkers and characterization of tumor microenvironment interactions in tumor evolution.

Bioelectronic control of a microbial community using surface-assembled electrogenetic cells to route signals.

We developed a bioelectronic communication system that is enabled by a redox signal transduction modality to exchange information between a living cell-embedded bioelectronics interface and an engineered microbial network. A naturally communicating three-member microbial network is 'plugged into' an external electronic system that interrogates and controls biological function in real time. First, electrode-generated redox molecules are programmed to activate gene expression in an engineered population of electrode-attached bacterial cells, effectively creating a living transducer electrode. These cells interpret and translate electronic signals and then transmit this information biologically by producing quorum sensing molecules that are, in turn, interpreted by a planktonic coculture. The propagated molecular communication drives expression and secretion of a therapeutic peptide from one strain and simultaneously enables direct electronic feedback from the second strain, thus enabling real-time electronic verification of biological signal propagation. Overall, we show how this multifunctional bioelectronic platform, termed a BioLAN, reliably facilitates on-demand bioelectronic communication and concurrently performs programmed tasks.

Biofunctionalized Cellulose Nanofibrils Capable of Capture and Antiadhesion of Fimbriated Escherichia coli.

In this study, naturally derived cellulose nanofibrils (CNFs), a renewable and easily modified nanomaterial with low cytotoxicity, were rendered bioactive via one-step functionalization with mannopyranoside (CNFs-mannose) for use as a new glyconanomaterial platform for control of bacterial pathogenesis. The recognition affinity of the bioactive surfaces toward fimbriated Escherichia coli was assessed using genetically engineered strains as well as wild-type (WT) MG1655 bacteria. The results revealed high surface coverages of FimH+ (with overexpressed FimH) and WT bacteria on the films of CNFs-mannose due to specific interaction between prevalent mannose on nanofibrils and FimH receptors on E. coli fimbriae. The CNFs-mannose nanofibrils were capable of capturing E. coli from a liquid suspension, as demonstrated either by the nanofibril clusters or by the cellulose filter papers impregnated with CNFs-mannose. More importantly, CNFs-mannose efficiently inhibited adhesion of both FimH+ and WT E. coli to mannosylated surfaces even at a very low concentration, resulting in over 95% reduction of bacterial adhesion. Furthermore, the bioactive nanofibrils showed effective disruption of nonspecific binding of bacteria to abiotic surfaces in flow channel tests. These findings highlight the potential of cellulose nanofibrils as a biocompatible polyvalent nanoscale scaffold and exemplify sugar grafted nanofibrils as novel and effective tools in control of bacterial pathogenesis, bacterial removal, as well as in many other applications.

A new design for an artificial cell: polymer microcapsules with addressable inner compartments that can harbor biomolecules, colloids or microbial species.

Eukaryotic cells have an architecture consisting of multiple inner compartments (organelles) such as the nucleus, mitochondria, and lysosomes. Each organelle is surrounded by a distinct membrane and has unique internal contents; consequently, each organelle has a distinct function within the cell. In this study, we create biopolymer microcapsules having a compartmentalized architecture as in eukaryotic cells. To make these capsules, we present a biocompatible method that solely uses aqueous media (i.e., avoids the use of oil phases), requires no sacrificial templates, and employs a minimal number of steps. Our approach exploits the electrostatic complexation of oppositely charged polymers dissolved in aqueous media. Specifically, droplets of an anionic biopolymer are generated using a simple microcapillary device, with the droplets being sheared off the capillary tip by pulses of gas (air or nitrogen). The liquid droplets are then introduced into a reservoir whereupon they encounter multivalent cations as well as a cationic biopolymer; thereby, a solid shell is formed around each droplet by electrostatic interactions between the polymers while the core is ionically cross-linked into a gel. In the next step, a discrete number of these capsules are encapsulated within a larger outer capsule by repeating the same process with a wider capillary. Our approach allows us to control the overall diameter of these multicompartment capsules (MCCs) (∼300-500 µm), the diameters of the inner compartments (∼100-300 µm), and the number of inner compartments in an MCC (1 to >5). More importantly, we can encapsulate different payloads in each of the inner compartments, including colloidal particles, enzymes, and microbial cells, in all cases preserving their native functions. A hallmark of biological cells is the existence of cascade processes, where products created in one organelle are transported and used in another. As an initial demonstration of the capabilities afforded by our MCCs, we study a simple cascade process involving two strains of bacteria (E. coli), which communicate through small molecules known as autoinducers. In one compartment of the MCC, we cultivate E. coli that produces autoinducer 2 (AI-2) in the presence of growth media. The AI-2 then diffuses into an adjacent compartment within the MCC wherein a reporter strain of E. coli is cultivated. The reporter E. coli imbibes the AI-2 and in turn, produces a fluorescence response. Thus, the action (AI-2 production) and response (fluorescence signal) are localized within different compartments in the same MCC. We believe this study is an important advance in the path towards an artificial cell.

Using a Redox Modality to Connect Synthetic Biology to Electronics: Hydrogel-Based Chemo-Electro Signal Transduction for Molecular Communication.

A hydrogel-based dual film coating is electrofabricated for transducing bio-relevant chemical information into electronical output. The outer film has a synthetic biology construct that recognizes an external molecular signal and transduces this input into the expression of an enzyme that converts redox-inactive substrate into a redox-active intermediate, which is detected through an amplification mechanism of the inner redox-capacitor film.

"Living" dynamics of filamentous bacteria on an adherent surface under hydrodynamic exposure.

The potential advantages of cell-based biohybrid devices over conventional nonliving systems drive the interest to control the behavior of the underlying biological cells in microdevices. Here, the authors studied how shear influenced the geometry and elongation of fimbriated filaments on affinity substrates. The cells were engineered to express FimH, which binds to mannose with a high affinity. A microfluidic channel was functionalized with RNAse B, which is rich in mannose residues, and the device was used to control the hydrodynamic force on live Escherichia coli under filamentous growth. It was discovered that filamentous E. coli cells adopt buckled geometry when the shear rate is low, but assume an extended geometry at high shear and align with the flow direction. The extension moves from bidirectional to preferentially downstream as the shear rate increases. Furthermore, living filaments slide easily on the substrate, and detach from the substrates at a rate nearly ten times greater than unfilamented live E. coli at high shear conditions (1000-4000 s-1). The hydrodynamic force and binding force experienced by the cells are further analyzed by COMSOL simulation and atomic force microscopy measurements, respectively, to explore the mechanism behind the living cell dynamics. Knowledge from this work helps guide design of interfacial properties and shear environments to control the geometry of living filamentous bacteria.

Connecting Biology to Electronics: Molecular Communication via Redox Modality.

Biology and electronics are both expert at for accessing, analyzing, and responding to information. Biology uses ions, small molecules, and macromolecules to receive, analyze, store, and transmit information, whereas electronic devices receive input in the form of electromagnetic radiation, process the information using electrons, and then transmit output as electromagnetic waves. Generating the capabilities to connect biology-electronic modalities offers exciting opportunities to shape the future of biosensors, point-of-care medicine, and wearable/implantable devices. Redox reactions offer unique opportunities for bio-device communication that spans the molecular modalities of biology and electrical modality of devices. Here, an approach to search for redox information through an interactive electrochemical probing that is analogous to sonar is adopted. The capabilities of this approach to access global chemical information as well as information of specific redox-active chemical entities are illustrated using recent examples. An example of the use of synthetic biology to recognize external molecular information, process this information through intracellular signal transduction pathways, and generate output responses that can be detected by electrical modalities is also provided. Finally, exciting results in the use of redox reactions to actuate biology are provided to illustrate that synthetic biology offers the potential to guide biological response through electrical cues.

Directed assembly of a bacterial quorum.

Many reports have elucidated the mechanisms and consequences of bacterial quorum sensing (QS), a molecular communication system by which bacterial cells enumerate their cell density and organize collective behavior. In few cases, however, the numbers of bacteria exhibiting this collective behavior have been reported, either as a number concentration or a fraction of the whole. Not all cells in the population, for example, take on the collective phenotype. Thus, the specific attribution of the postulated benefit can remain obscure. This is partly due to our inability to independently assemble a defined quorum, for natural and most artificial systems the quorum itself is a consequence of the biological context (niche and signaling mechanisms). Here, we describe the intentional assembly of quantized quorums. These are made possible by independently engineering the autoinducer signal transduction cascade of Escherichia coli (E. coli) and the sensitivity of detector cells so that upon encountering a particular autoinducer level, a discretized sub-population of cells emerges with the desired phenotype. In our case, the emergent cells all express an equivalent amount of marker protein, DsRed, as an indicator of a specific QS-mediated activity. The process is robust, as detector cells are engineered to target both large and small quorums. The process takes about 6 h, irrespective of quorum level. We demonstrate sensitive detection of autoinducer-2 (AI-2) as an application stemming from quantized quorums. We then demonstrate sub-population partitioning in that AI-2-secreting cells can 'call' groups neighboring cells that 'travel' and establish a QS-mediated phenotype upon reaching the new locale.