Hiroshi Y. Yoshikawa

Use of lasers has increasingly been recognized as a promising tool for the spatiotemporal control of crystallization, which is required in various scientific and industrial fields. This work reports synergistic enhancement of crystal nucleation by spatially patterned multi-spot laser irradiation, which drastically improves crystallization efficiency from melt and solutions. We found that pulsed laser irradiation at two different spots with a certain separation distance could significantly enhance ice crystal nucleation in supercooled water, where no nucleation could be induced by single-spot irradiation with the doubled pulse energy. Furthermore, we revealed that not only the inter-spot distance but also the spatial geometry of laser-induced stimuli is critical for the enhancement of ice crystal nucleation, suggesting that multi-spot irradiation enhances nucleation by the synergistic interplay of multiple cavitation bubbles and/or pressure waves that were generated from different laser spots. Such crystal nucleation enhancement by multi-spot laser irradiation was also confirmed in a solution system. These results clearly indicate that crystallization probability is governed not simply by the total laser energy delivered to the solution but by its spatial distribution, which provides a practical design guideline for efficient spatially patterned laser-induced nucleation and mechanistic insight into precise crystallization control.

Despite substantial advances in understanding urinary stone formation, including mechanisms of calcium phosphate (CaP) crystallization, tissue infiltration, and stone development via Randall’s plaques, the global prevalence of urolithiasis continues to rise and current knowledge has only limited impact on clinical outcomes. This study focuses on the CaP phase, particularly brushite, and re-examines its role under physiologically relevant conditions as a potential key to more effective prevention. The aim was to elucidate how reactions proceed near the surfaces of brushite crystals that can present in urine, and how these reactions are modulated by coexisting proteins, using wide-field optical observation combined with quantitative modeling. Single-crystal brushite was immersed in a model solution pre-equilibrated with calcium oxalate monohydrate (COM), and the time evolution of the Ca2+ concentration field associated with brushite dissolution was evaluated by in situ microscopy and one-dimensional diffusion analysis. The results demonstrated that brushite dissolution generates a critical Ca2+ supersaturation zone extending several hundred micrometers from the crystal surface, within which COM nucleation occurs. Upon addition of bovine serum albumin (BSA) as a model protein, the average growth of COM was inhibited, whereas the local frequency of COM nucleation increased markedly in regions of the brushite surface with high step and kink densities, yielding dense, rigid COM−brushite composites. These findings indicate that brushite crystals function not merely as apatite precursors, but as localized “reaction fields” that spatially control calcium oxalate nucleation, aggregation, and consolidation. Furthermore, urinary proteins can, through these fields, act not only as inhibitors but also as local promoters of stone formation.

Coordinated neuronal population activity is essential for brain function, yet how such network-level organization emerges during development remains incompletely understood. Here, we conducted whole-cerebellar calcium imaging at cellular scale in zebrafish larvae to investigate the developmental maturation of Purkinje cell population dynamics. Visual stimulation evoked large, spatially organized Purkinje cell clusters driven by inferior olive inputs and accompanied by coherent optokinetic behavior. In the absence of stimuli, Purkinje cells formed transient assemblies exhibiting distance-dependent coordination. During development, long-range coordination progressively emerged, transforming locally correlated activity into distributed cerebellar population dynamics. Early enucleation, but not dark rearing, disrupted this developmental acquisition of long-range coordination and induced aberrant population clustering, indicating a retina-dependent mechanism underlying cerebellar network formation. Together, our findings reveal key organizational features underlying the developmental emergence of coordinated cerebellar population dynamics and suggest that early retina-dependent signals shape population-level organization.

The spatial distribution of the temperature of aqueous solutions under the conditions of laser trapping for molecular assembly was systematically evaluated. Recent studies have revealed that laser trapping (also called optical tweezers) is a powerful tool not only for manipulating micro/nanoparticles but also for controlling molecular assembly, such as crystallization. However, laser trapping for molecular assembly usually requires focused laser irradiation with a power of ∼1.0 W, which should cause a higher temperature elevation in a larger region compared to that for conventional optical tweezers (<0.1 W). In this work, the ratio metric measurement of thermoresponsive fluorescent protein revealed the actual spatial distribution of temperature rise in a relatively wide field of view (∼100 μm) and a wide range of irradiation time (seconds to minutes) at the laser power of 0.1-1.0 W, highlighting the impact of temperature elevation on molecular assembly over the laser focal spot size (∼1 μm). We also found the confinement of photothermally generated clusters by laser trapping at the laser focus, which indicates a synergistic interplay of laser trapping and photothermal effects on the aggregation of thermoresponsive polymers above the lower critical solution temperature. We foresee that the photothermal effects on molecular assembly studied in this work should enhance the understanding of the underlying mechanisms of molecular accumulation/aggregation induced by laser trapping.

Spatiotemporal control of the formation of highly ordered, protein fiber assemblies via photophysical effects of a focused laser beam is demonstrated. Focused irradiation with a continuous laser beam at an air/solution interface can accumulate tubulin proteins at/around the laser focus, which leads to the formation of highly ordered microtubule assemblies. The assemblies can exhibit various dynamic behaviors such as translational motion, bundling, and cilia‐like beating with motor protein and chemical energy, revealing their biological activities. The protein accumulation with a focused laser beam is attributed to the local increases in concentration and temperature produced through two‐types of photophysical effects, i.e., laser trapping by optical forces and heat generation by photoabsorption, which can fabricate complex microtubule assemblies without specific photochemical reactions and deuterated water solvents (i.e., physiological conditions). We anticipate that this laser method will provide fundamental insights into the structure‐motion relationship of biomolecular assemblies and expand the bioengineering of protein assemblies.

Precise control of nucleation pathways under nonequilibrium optical trapping conditions remains a fundamental challenge. Here, we report an enantiomer-specific reversal in phase selection during the optical trapping-induced crystallization of binary systems containing acetaminophen and either l- or d-phenylalanine. Switching the handedness of circularly polarized light reverses the dominant product between a thermodynamically stable cocrystal and a metastable phenylalanine phase. In situ Raman spectroscopy reveals constant local stoichiometry during irradiation, indicating the absence of a macroscopic polarization-induced concentration gradient. Instead, the results are consistent with a proposed mechanism where phase selection is driven by a polarization-dependent kinetic bias under strongly nonequilibrium conditions. We propose that this bias originates from subtle differences in the residence dynamics of transient nanoscale clusters within the optical trapping field, which are statistically amplified over time. These findings highlight a sophisticated kinetic route for controlling crystallization beyond conventional thermodynamic strategies.

Mesenchymal progenitors are essential for muscle regeneration, but also contribute to fat accumulation and fibrosis. Several extrinsic and intrinsic factors regulating adipogenic or fibrogenic differentiation of mesenchymal progenitors have been identified, but it remains unclear how different cues are integrated to determine cell fate. Here, we demonstrate that interstitial stiffness and the mechanosensitive hippo pathway regulate mesenchymal progenitor cell fate. Fat accumulation model reduces interstitial stiffness and nuclear YAP/TAZ-positive mesenchymal progenitors compared to a regeneration model, whereas YAP/TAZ deficiency in mesenchymal progenitors enhances fat deposition. Mechanistically, YAP/TAZ directly induce expression of the anti-adipogenic genes Aldh1a2 and Wnt5a, and the pro-fibrogenic gene Tgfbr2, mediating TGF-β binding. Loss of Tgfbr2 in mesenchymal progenitors reduced transient collagen deposition, decreased stiffness, and increased fat accumulation during regeneration. We propose a stiffness–YAP/TAZ–Tgfbr2–collagen regulatory loop governing mesenchymal progenitor cell fate and highlight its importance for optimal muscle regeneration.