Herdeline Ann M. Ardona

Supramolecular peptide assemblies provide versatile, functional material platforms with structures and properties that can be regulated by molecular design and external stimuli. Monitoring their structural evolution is therefore important for tracking trigger-induced reorganization, and thus property changes, during the assembly process. Here, we introduce near-infrared (NIR) fluorescent single-walled carbon nanotube (SWCNT) optical reporters as probes of trigger-induced peptide self-assembly in aqueous environments. We employ the π-conjugated peptide DVV4T, a quaterthiophene (4T)-Asp–Val–Val unit, as a model system that undergoes electrostatically regulated supramolecular reorganization while simultaneously acting as a noncovalent dispersant for SWCNTs. Exposure to distinct chemical triggers induces self-assembly of DVV4T, which incorporates the peptide-SWCNT hybrids into the resulting supramolecular structures. Electron microscopy reveals trigger-specific morphologies, ranging from bundled filaments to extended, interconnected networks of peptide-SWCNTs. These self-assembly transformations produce trigger-specific, chirality-resolved, time-dependent modulations in the SWCNT NIR fluorescence, enabling optical readouts of supramolecular restructuring within the NIR biologically transparent spectral window. Together, these results establish SWCNTs as information-rich optical transducers of stimulus-responsive peptide self-assembly and highlight their potential for tracking dynamic supramolecular reorganization in adaptive functional nanomaterials.

Engineering physiologically relevant cardiac substrates requires precise control over both electrical and mechanical cues to guide cardiomyocyte functions and features. In this work, we report a biomolecular-based approach toward spatially controllable photostimulation of cardiac behavior via digital light processing of conductive interfaces on a range of substrate stiffnesses. The symmetric peptide-quaterthiophene-peptide units are designed to form conductive patterns atop biopolymeric hydrogels, allowing for microscale spatial control of photoconductive pathways that can influence cardiomyocyte alignment and intercellular communication in a light-activated manner. Substrate stiffness was modulated through adjusting material composition across a physiologically relevant range to reflect healthy and fibrotic cardiac tissue conditions. The ability to tailor the geometry of conductive pathways across a range of biomaterial interfaces and stiffnesses enables systematic assessment of how electrical signals from patterned optoelectronic peptides regulate cardiomyocyte behavior. Neonatal rat ventricular myocytes (NRVMs) cultured on π-conjugated peptide-based substrates exhibited enhanced alignment, synchronous contractility, and altered calcium flux dynamics compared to nonconductive substrates. Furthermore, the optoelectronic cardiac biomaterial-based scaffolds were shown to possess biological photostimulation capabilities, specifically enabling light-induced localized stimulation of excitable cells for high-resolution stimulation without the need for external electrodes or genetic modifications necessary for optogenetic approaches. Photostimulated NRVMs interfaced with optoelectronic peptide structures were shown to be more confined to the printed conductive patterns, with more cell localization and structural remodeling with respect to the patterns than in non-photostimulated conditions. The peptide-based platform presented here provides a potential approach to control mechanical and optoelectronic cues using microscale patterns in vitro, while opening avenues for advanced cardiac disease modeling, drug development, and the development of complex bioelectronic cardiac interfaces.

Cerebral cortex organoids are powerful in vitro models that recapitulate key features of human development. However, conventional methods produce cortical organoids with spontaneous, spatially disorganized cortical regions due to limited control over morphogen distribution within local environments. Here, we present a spatially engineered hydrogel platform that drives localized formation of posterior signaling centers in cortical organoids through controlled, localized exposure to morphogens. Using a combination of bulk photopolymerization, thermal crosslinking, and digital light processing (DLP) approaches, we fabricated hydrogels with stiffness-controlled layers that preferentially deliver morphogens to one side of the organoid, selectively inducing the expression of posterior markers on the exposed face. We further validated this platform by delivering fluorescently tagged dextran, used as molecular weight-matched model morphogens, to visualize spatiotemporal delivery dynamics at the organoid interface. As a proof of principle, we also demonstrated that DLP fabrication enables the printing of dual morphogen hubs, serving as a model for establishing two opposing gradients within a single organoid. Together, this hydrogel platform enables systematic spatial patterning of cell populations in organoids, more faithfully recapitulating the spatial organization and cellular diversity of native tissues and advancing higher-fidelity models for studying human development and disease.

We demonstrate the use of muscular thin films (MTFs) as a hydrodynamic assay to measure cardiac stroke volume on a chip, and quantify changes in response to ionotropic dosing; helping bridge the gap between in vitro and in vivo measurements.

Charge and energy transport within living systems are fundamental processes that enable the autonomous function of excitable cells and tissues. To date, localized control of these transport processes has been enabled by genetic modification approaches to render light sensitivity to cells. Here, we present peptidic nanoassemblies as constituents of a cardiac biomaterial platform that leverages complementary sequence interactions to direct photoinduced energy transport at the cellular interface. Photophysical characterizations and conductivity measurements confirm the occurrence of energy/charge transfer and photocurrent generation upon optical excitation in both dry and electrolytic environments. Comparing an electrostatic sequence pair against a sequence-matched donor–acceptor coassembly, we demonstrate that the sequence design with charge complementarity shows more prominent photocurrent behavior. With the flanking bioadhesive units, the primary and stem cell–derived cardiomyocytes interfaced with covalently stabilized films of the optoelectronic nanostructures exhibited material-stimulated genotypic, structural, or functional cardiac features. Collectively, our findings introduce an optoelectronic cardiac biomaterial where coassembled peptide nanostructures are molecularly designed to induce light sensitivity in excitable cells without gene modification, influencing in vitro cardiac contractile behavior and expression of cardiac markers.

The propagation of electrical signals in the human heart relies on organized conduction pathways to optimally function and pump blood into the rest of the body. Mimicking this directionality across interconnected myocytes in vitro is currently achieved by patterning the cells themselves, which are often subjected to external stimulatory cues that are rarely localized or have controlled anisotropy. Here, we demonstrate an approach to interface micropatterned optoelectronic peptides with cardiomyocytes, whereby the engineered biomolecular structures dictate the organization of cells in a substrate, while also presenting photocurrent-generating electrodes of defined microscale geometries. To this end, we utilized surface modification strategies that allowed for the creation of stable micropatterns of quaterthiophene-bearing peptide assemblies on both glass (∼GPa range) and gelatin hydrogel (∼20 kPa) substrates that last for multiple days within an aqueous environment. The pH-sensitive assembly behavior of π-conjugated peptides was also investigated as to how it evolves at various stages of the patterning process and impacts material scattering once they are imprinted on different substrates. Neonatal rat ventricular myocytes (NRVMs) seeded on gelatin scaffolds that had been interfaced with π-conjugated peptide micropatterns saw improvements to their orientational order parameter (OOP) of both the actin cytoskeleton and z-lines, which were not observed for those cultured on isotropic controls or on microgrooved gelatin samples. Additionally, the micropatterned π-conjugated peptide platform was shown to exhibit photocurrent-generating properties on both gelatin and glass substrates in aqueous cell culture environments. The peptide-based platform discussed here provides a potential approach to confine conductive biomaterials within microscale features in vitro while simultaneously providing an avenue for light-based localized stimulation of electroactive tissues.

This work presents a strategy for generating composite hydrogels bearing photoconductive conduits held by supramolecular interactions that are compatible with digital light processing (DLP) printing. Conductive polymers are typically processed with organic solvents as the film, yet if used as biomaterials, excitable cells often require matching with the mechanical and structural properties of their native, aqueous three-dimensional (3-D) microenvironment. Here, we utilize peptide-functionalized porphyrin units capable of self-assembling into photoconductive nanostructures with defined nanomorphologies under aqueous conditions. In addition to the DXXD peptide arms (X = V, F), the sequence variants studied here include a peptidic moiety bearing allyloxycarbonyl (alloc) groups that can serve as crosslinking sites of the acrylate-based monomers that ultimately form the base 3-D covalent network for the hydrogels. We investigate the impact of pre-templating polymeric gelators with supramolecular assemblies vs. printing a dispersed peptide–porphyrin in a polymer composite, specifically, the potential impact of the morphologies of the supramolecular additives or “dopants” on the resulting mechanical property, conductivity, and printability of the hydrogels, comprised of a hybrid between acrylated polymers and supramolecular peptide–porphyrin assemblies. Lastly, we demonstrate the role of photophysical properties that emerge from peptide-tuned porphyrin assemblies as a photoabsorber additive that influences the printing outcomes of the composite hydrogel. Overall, we present a covalent-supramolecular composite hydrogelator system where the self-assembled networks offer a pathway for energy transport and mechanical reinforcement/dissipation at the same time, leading to the formation of a hydrogel with optoelectronic, mechanical, and printable behavior that can be influenced by self-assembled dopants.

In biomimetic design, researchers recreate existing biological structures to form functional devices. For biohybrid robotic swimmers assembled with tissue engineering, this is problematic because most devices operate at different length scales than their naturally occurring counterparts, resulting in reduced performance. To overcome these challenges, here, we demonstrate how machine learning–directed optimization (ML-DO) can be used to inform the design of a biohybrid robot, outperforming other nonlinear optimization techniques, such as Bayesian optimization, in the selection of high-performance geometries. We show how this approach can be used to maximize the thrust generated by a tissue-engineered mobuliform miniray. This results in devices that can swim at the millimeter scale while more closely preserving natural locomotive scaling laws. Overall, this work provides a quantitatively rigorous approach for the engineering design of muscular structure-function relationships in an automated fashion.