Implantable Optofluidic Systems for Wireless In Vivo Photopharmacology

Enhancing biocompatibility of the brain-machine interface: A review

In vivo implantation of microelectrodes opens the door to studying neural circuits and restoring damaged neural pathways through direct electrical stimulation and recording. Although some neuroprostheses have achieved clinical success, electrode material properties, inflammatory response, and glial scar formation at the electrode-tissue interfaces affect performance and sustainability. Those challenges can be addressed by improving some of the materials' mechanical, physical, chemical, and electrical properties. This paper reviews materials and designs of current microelectrodes and discusses perspectives to advance neuroprosthetics performance.

In vivo photopharmacological inhibition of hippocampal activity via multimodal probes - perspective and opening steps on experimental and computational challenges

Neurological conditions such as epilepsy can have a significant impact on people's lives. Here, we discuss a new perspective for the study/treatment of these conditions using photopharmacology. A multimodal, intracranial implant that incorporates fluidic channels for localised drug delivery, electrodes for recording and stimulation, and a light source for photoswitching is used for in vivo administration and deactivation of a photoresponsive AMPA antagonist. We review current advancements in the relevant disciplines and show experimentally that the inhibition of seizure-like events induced in the hippocampus by electrical stimulation can be altered upon switching the drug with light. We discuss the interconnection of the drug's photopharmacological properties with the design of the device by modelling light penetration into the rat brain with Monte Carlo simulations. This work delivers a new perspective, including initial experimental and computational efforts on in vivo photopharmacology to understand and eventually treat neurological conditions.

Smart photopharmacological agents: LaVO4:Eu3+@vinyl phosphonate combining luminescence imaging and photoswitchable butyrylcholinesterase inhibition

The combination of photoswitchability and bioactivity in one compound provides interesting opportunities for photopharmacology. Here, we report a hybrid compound that in addition allows for its visual localization. It is the first demonstration of its kind and it even shows high photoswitchability. The multifunctional nanomaterial hybrid, which we present, is composed of luminescent LaVO4:Eu3+ nanoparticles and vinyl phosphonate, the latter of which inhibits butyrylcholinesterase (BChE). This inhibition increases 7 times when irradiated with a 266 nm laser. We found that it is increased even further when vinyl phosphonate molecules are conjugated with LaVO4:Eu3+ nanoparticles, leading in total to a 20-fold increase in BChE inhibition upon laser irradiation. The specific luminescence spectrum of LaVO4:Eu3+ allows its spatial localization in various biological samples (chicken breast, Daphnia and Paramecium). Furthermore, laser irradiation of the LaVO4:Eu3+@vinyl phosphonate hybrid leads to a drop in luminescence intensity and in lifetime of the Eu3+ ion that can implicitly indicate photoswitching of vinyl phosphonate in the bioactive state. Thus, combining enhanced photoswitchability, bioactivity and luminescence induced localizability in a unique way, hybrid LaVO4:Eu3+@vinyl phosphonate can be considered as a promising tool for photopharmacology.

Fluidic enabled bioelectronic implants: opportunities and challenges

Bioelectronic implants are increasingly facilitating novel strategies for clinical diagnosis and treatment. The integration of fluidic technologies into such implants enables new complementary routes for sensing and therapy alongside electrical interaction. Indeed, these two technologies, electrical and fluidic, can work synergistically in a bioelectronics implant towards the fabrication of a complete therapeutic platform. In this perspective article, the leading applications of fluidic enabled bioelectronic implants are highlighted and methods of operation and material choices are discussed. Furthermore, a forward-looking perspective is offered on emerging opportunities as well as critical materials and technological challenges.

Orthogonal Control of Neuronal Circuits and Behavior Using Photopharmacology

Over the last decades, photopharmacology has gone far beyond its proof-of-concept stage to become a bona fide approach to study neural systems in vivo. Indeed, photopharmacological control has expanded over a wide range of endogenous targets, such as receptors, ion channels, transporters, kinases, lipids, and DNA transcription processes. In this review, we provide an overview of the recent progresses in the in vivo photopharmacological control of neuronal circuits and behavior. In particular, the use of small aquatic animals for the in vivo screening of photopharmacological compounds, the recent advances in optical modulation of complex behaviors in mice, and the development of adjacent techniques for light and drug delivery in vivo are described.

A guide to designing photocontrol in proteins: methods, strategies and applications

Light is essential for various biochemical processes in all domains of life. In its presence certain proteins inside a cell are excited, which either stimulates or inhibits subsequent cellular processes. The artificial photocontrol of specifically proteins is of growing interest for the investigation of scientific questions on the organismal, cellular and molecular level as well as for the development of medicinal drugs or biocatalytic tools. For the targeted design of photocontrol in proteins, three major methods have been developed over the last decades, which employ either chemical engineering of small-molecule photosensitive effectors (photopharmacology), incorporation of photoactive non-canonical amino acids by genetic code expansion (photoxenoprotein engineering), or fusion with photoreactive biological modules (hybrid protein optogenetics). This review compares the different methods as well as their strategies and current applications for the light-regulation of proteins and provides background information useful for the implementation of each technique.

Analytical Modeling of Flowrate and Its Maxima in Electrochemical Bioelectronics with Drug Delivery Capabilities

Flowrate control in flexible bioelectronics with targeted drug delivery capabilities is essential to ensure timely and safe delivery. For neuroscience and pharmacogenetics studies in small animals, these flexible bioelectronic systems can be tailored to deliver small drug volumes on a controlled fashion without damaging surrounding tissues from stresses induced by excessively high flowrates. The drug delivery process is realized by an electrochemical reaction that pressurizes the internal bioelectronic chambers to deform a flexible polymer membrane that pumps the drug through a network of microchannels implanted in the small animal. The flowrate temporal profile and global maximum are governed and can be modeled by the ideal gas law. Here, we obtain an analytical solution that groups the relevant mechanical, fluidic, environmental, and electrochemical terms involved in the drug delivery process into a set of three nondimensional parameters. The unique combinations of these three nondimensional parameters (related to the initial pressure, initial gas volume, and microfluidic resistance) can be used to model the flowrate and scale up the flexible bioelectronic design for experiments in medium and large animal models. The analytical solution is divided into (1) a fast variable that controls the maximum flowrate and (2) a slow variable that models the temporal profile. Together, the two variables detail the complete drug delivery process and control using the three nondimensional parameters. Comparison of the analytical model with alternative numerical models shows excellent agreement and validates the analytic modeling approach. These findings serve as a theoretical framework to design and optimize future flexible bioelectronic systems used in biomedical research, or related medical fields, and analytically control the flowrate and its global maximum for successful drug delivery.