Dynamics of firing patterns,synchronization and resonances in neuronal electrical activities:experiments and analysis

Recent advances in the experimental and theoretical study of dynamics of neuronal electrical firing activities are reviewed. Firstly, some experimental phenomena of neuronal irregular firing patterns, especially chaotic and stochastic firing patterns, are presented, and practical nonlinear time analysis methods are introduced to distinguish deterministic and stochastic mechanism in time series. Secondly, the dynamics of electrical firing activities in a single neuron is concerned, namely, fast-slow dynamics analysis for classification and mechanism of various bursting patterns, one- or two-parameter bifurcation analysis for transitions of firing patterns, and stochastic dynamics of firing activities （stochastic and coherence resonances, integer multiple and other firing patterns induced by noise, etc.）. Thirdly, different types of synchronization of coupled neurons with electrical and chemical synapses are discussed. As noise and time delay are inevitable in nervous systems, it is found that noise and time delay may induce or enhance synchronization and change firing patterns of coupled neurons. Noise-induced resonance and spatiotemporal patterns in coupled neuronal networks are also demonstrated. Finally, some prospects are presented for future research. In consequence, the idea and methods of nonlinear dynamics are of great significance in exploration of dynamic processes and physiological functions of nervous systems.

Multi-stability involved mixed bursting within the coupled pre-Btzinger complex neurons

Neurons in the pre-B6tzinger complex within the mammalian brain stem play important roles in the generation of respiratory rhythms. Experimental observations show that some neurons can exhibit novel mixed bursting activities. In this paper, based on a mathematical model proposed by Butera, we show how the mixed bursting activities depend on the potassium current in the coupled pre-Botzinger complex. Using fast-slow decomposition and bifurcation analysis, we investigate the dynamics of mixed bursting, as well as the mechanisms of transition between different mixed bursting patterns. We find that mixed bursting involves different bistability, and it is the transition state of two types of regular burstings.

Current hydrogel advances in physicochemical and biological response-driven biomedical application diversity

Hydrogel is a type of versatile platform with various biomedical applications after rational structure and functional design that leverages on material engineering to modulate its physicochemical properties(e.g.,stiffness,pore size,viscoelasticity,microarchitecture,degradability,liga nd prese ntation,stimulus-resp on sive properties,etc.)and in flue nee cell signaling cascades and fate.In the past few decades,a plethora of pioneering studies have been implemented to explore the cell-hydrogel matrix interactions and figure out the underlying mechanisms,paving the way to the lab-to-clinic translation of hydrogel-based therapies.In this review,we first introduced the physicochemical properties of hydrogels and their fabrication approaches concisely.Subsequently,the comprehensive description and deep discussion were elucidated,wherein the influences of different hydrogels properties on cell behaviors and cellular signaling eve nts were highlighted.These behaviors or events in eluded integrin clustering,focal adhesion(FA)complex accumulation and activation,cytoskeleton rearrangement,protein cyto-nuelei shuttling and activation(e.g.,Yes-associated protein(YAP),catenin,etc.),cellular compartment reorganization,gene expression,and further cell biology modulation(e.g.,spreading,migration,proliferation,lineage commitment,etc.).Based on them,current in vitro and in vivo hydrogel applications that mainly covered diseases models,various cell delivery protocols for tissue regeneration and disease therapy,smart drug carrier,bioimaging,biosensor,and conductive wearable/implantable biodevices,etc.were further summarized and discussed.More significantly,the dinical translation potential and trials of hydrogels were presented,accompanied with which the remaining challenges and future perspectives in this field were emphasized.Collectively,the comprehe nsive and deep in sights in this review will shed light on the design principles of new biomedical hydrogels to understand and modulate cellular processes,which are available for providing significant indications for future hydrogel design and serving for a broad range of biomedical applications.