Bidirectional Transfer Research Articles

A high effectiveness impact‐optimized piezoelectric energy harvesting interface system

AbstractThis paper presents a novel high‐performance impact‐optimized interface system for an impact‐driven piezoelectric energy harvester (PEH) which utilizes two independent parallel harvesting plans, that is, low‐efficiency self‐powered passive path and high‐efficiency active maximum power point tracking (MPPT)‐based path, for different situations based on the characteristics of the input excitation and stored energy content which are evaluated by the mode detection unit. It uses a synchronous electrical charge extraction‐based self‐powered passive circuit as a primary energy extraction strategy. Thus, the proposed structure is self‐sustained with cold start capability. When the determined prerequisites are met, the system switches to the secondary energy extraction strategy, that is, high‐efficiency MPPT‐based path, in which during the maximum power point sensing phase, the PEH is sensed without disconnecting it from the interface and during the maximum power point setting phase, a bidirectional DC/DC converter performs a fully bidirectional energy transfer, increasing the extraction efficiency. The proposed system is designed and simulated using standard 180 nm complementary metal‐oxide semiconductor (CMOS) technology. Post‐layout simulation results show that when the input energy content is around 50 µJ, the FoMMOPIR, periodic harvesting efficiency, shock harvesting efficiency, MPPT efficiency, and effectiveness of the proposed system are 505%, 65%, 80%, 70%, and 56%, respectively.

Analysis and Implementation of Underwater Single Capacitive Coupled Simultaneous Wireless Power and Bidirectional Data Transfer System

Analysis and Implementation of Underwater Single Capacitive Coupled Simultaneous Wireless Power and Bidirectional Data Transfer System

Triple Phase Shift Modulation Scheme for Bidirectional Wireless Power Transfer Systems With Efficiency Maximization

Triple Phase Shift Modulation Scheme for Bidirectional Wireless Power Transfer Systems With Efficiency Maximization

Controlling Hydrogen Evolution and CO2 Reduction at Transition Metal Hydrides.

ConspectusFuel-forming reactions such as the hydrogen evolution reaction (HER) and CO2 reduction (CO2R) are vital to transitioning to a carbon-neutral economy. The equivalent oxidation reactions are also important for efficient utilization in fuel cells. Metal hydride intermediates are common in these catalytic and electrocatalytic processes. Guiding metal hydride reactivity is important for achieving selective, kinetically fast, and low overpotential redox reactions. Our work has focused on understanding kinetic and thermodynamic aspects for controlling these reactive hydride species in an effort to design more selective electrocatalysts that operate at low overpotentials. Key to our research approach is understanding the free energy changes and rate of discrete steps of catalysis through the synthesis of proposed intermediates to independently investigate catalytic steps. Hydricity, the free energy of hydride dissociation, and how these values change with metal and ligand environment have informed catalyst design in the past few decades. We describe here how we have advanced upon these earlier studies.In our early studies we sought to understand solvent-dependent changes in hydricity for transition metal hydrides and how they impact the free energy for reduction of CO2 to formate (HCO2-). Additionally, we described how hydricity values can be applied to optimize HER and CO2R catalysis. This framework provides general guidelines for achieving selective CO2 reduction to formate without concomitant generation of H2. Kinetic information on steps in the proposed catalytic cycle of HER and CO2R catalysts were evaluated to identify potential rate-determining steps. As a second approach to achieve selective reduction for CO2, we explored two catalyst design strategies to kinetically inhibit HER using electrostatic (charged) and steric interactions. Hydricity values and other considerations for minimizing the free energy of proposed catalytic steps were also used to design an electrocatalyst for the interconversion between CO2 and HCO2- at low overpotentials. Further, we discuss our efforts to translate the CO2 hydrogenation activity of homogeneous catalysts to electrocatalysis.All of these catalytic systems operate with classical metal hydrides, where the electrons and proton are colocated on the metal center. However, classical metal hydrides all require very reducing potentials to generate sufficiently strong hydride donors for CO2 reduction. An analysis of metal hydride hydricity and reduction potentials shows that the strong correlation between reduction potential and hydricity is a general trend because the former is also highly correlated to pKa. However, formate dehydrogenase (FDH) generates a competent hydride donor at more mild potentials through bidirectional hydride transfer, where the proton and electrons of the hydride are not colocated. This bioinspired approach points to a promising new strategy for generating strong hydride donors at milder potentials and will surely open new avenues for using hydricity as a guide for addressing new and existing problems in catalysis.

Bidirectional DC/DC Converter Based on Interleaved Parallel Buck/Boost Cascades CLLLC

ABSTRACTIn this paper, a two‐stage bidirectional DC/DC converter is suggested to handle the energy transfer for electric vehicles between high‐voltage and low‐voltage batteries. The converter enables bidirectional power transfer, a broad range of input voltage, and a high ratio of voltage. The front stage adopts the bidirectional CLLLC resonant converter, which possesses excellent soft switching characteristics because of its symmetrical structure in both forward and reverse directions. Open‐loop fixed frequency control is used in the forward direction to set the working frequency of the switching transistors near the resonance frequency, and the voltage and current double closed loop control is employed to achieve a constant voltage ratio and efficient power transmission in the reverse direction. The rear stage adopts an interleaved parallel bidirectional Buck/Boost converter, and the interleaved parallel structure helps to lessen the output current ripple. The duty cycle secondary distribution method is used on the basis of the voltage and current double closed loop control to regulate the output voltage and make the converter operate stably. The principle and characteristics of the bidirectional DC/DC converter are analyzed, and by modeling and experimentation, the theoretical analysis's viability and correctness are confirmed.

Triplet Energy Gap‐Regulated Room Temperature Phosphorescence in Host–Guest Doped Systems

AbstractThe organic room temperature phosphorescence (RTP) materials via host–guest doped method receive considerable attention in the fields of optoelectronics, bioimaging, and information encryption. Despite many host–guest doped materials with excellent RTP properties have been developed, their luminous mechanism is still limited. Here, a series of host–guest doped materials, using benzophenone as the host and quinone compounds as the guests, were constructed to investigate the effect of the triplet energy gap (ΔET) between the host and guest on triplet states population. The guest's triplet state is proposed to be a “triplet energy reservoir”, gathering the triplet excitons to emit RTP when ΔET is large and returning triplet excitons to the host when ΔET is small. By combining the results of steady‐state and delayed emission spectra, time‐resolved transient absorption spectra, and theoretical calculations, a bidirectional energy transfer process is proved, which are triplet‐triplet energy transfer and reverse triplet‐triplet energy transfer processes. The thermal equilibrium of these two energy transfer processes can be regulated by the ΔET and temperature. The potential applications of these RTP properties are also realized in data encryption and anti‐counterfeiting. This work provides valuable insight into the design of host–guest doped materials based on energy transfer mechanisms.

Triplet Energy Gap-Regulated Room Temperature Phosphorescence in Host-Guest Doped Systems.

The organic room temperature phosphorescence (RTP) materials via host-guest doped method receive considerable attention in the fields of optoelectronics, bioimaging, and information encryption. Despite many host-guest doped materials with excellent RTP properties have been developed, their luminous mechanism is still limited. Here, a series of host-guest doped materials, using benzophenone as the host and quinone compounds as the guests, were constructed to investigate the effect of the triplet energy gap (ΔET) between the host and guest on triplet states population. The guest's triplet state is proposed to be a "triplet energy reservoir", gathering the triplet excitons to emit RTP when ΔET is large and returning triplet excitons to the host when ΔET is small. By combining the results of steady-state and delayed emission spectra, time-resolved transient absorption spectra, and theoretical calculations, a bidirectional energy transfer process is proved, which are triplet-triplet energy transfer and reverse triplet-triplet energy transfer processes. The thermal equilibrium of these two energy transfer processes can be regulated by the ΔET and temperature. The potential applications of these RTP properties are also realized in data encryption and anti-counterfeiting. This work provides valuable insight into the design of host-guest doped materials based on energy transfer mechanisms.

Mechanisms Regulating Mitochondrial Transfer in Human Corneal Epithelial Cells.

The intraepithelial corneal nerves (ICNs) innervating the cornea are essential to corneal epithelial cell homeostasis. Rho-associated kinase (ROCK) inhibitors (RIs) have been reported to play roles in neuron survival after injury and in mitochondrial transfer between corneal epithelial cells. In this study, the mechanisms human corneal limbal epithelial (HCLE) cells use to control intercellular mitochondrial transfer are assessed. Mitotracker and AAV1 mitotag eGFPmCherry were used to allow us to study mitochondrial transfer between HCLE cells and neurons in co-cultures and in HCLE cultures. A mitochondrial transfer assay was developed using HCLE cells to quantify the impact of cell stress and inhibition of phagocytosis, gap junctions, and ROCK on mitochondrial transfer, cell adhesion, migration, matrix deposition, and mitochondrial content. Bidirectional mitochondrial transfer occurs between HCLE cells and neurons. Mitochondrial transfer among HCLE cells is inhibited when gap junction function is reduced and enhanced by acid stress and by inhibition of either phagocytosis or ROCK. Media conditioned by RI-treated cells stimulates cell adhesion and mitochondrial transfer. Maximal mitochondrial transfer takes place when gap junctions are functional, when ROCK and phagocytosis are inhibited, and when cells are stressed by low pH media. Treatments that reduce mitochondrial content increase HCLE cell mitochondrial transfer. ROCK inhibition in co-cultures causes the release and adhesion of mitochondria to substrates where they can be engulfed by migrating HCLE cells and growing axons and their growth cones.

RGB-D Data Compression via Bi-Directional Cross-Modal Prior Transfer and Enhanced Entropy Modeling

RGB-D data, being homogeneous cross-modal data, demonstrates significant correlations among data elements. However, current research focuses only on a unidirectional pattern of cross-modal contextual information, neglecting the exploration of bidirectional relationships in the compression field. Thus, we propose a joint RGB-D compression scheme, which is combined with Bi-directional Cross-modal Prior Transfer (Bi-CPT) modules and a Bi-directional Cross-modal Enhanced Entropy (Bi-CEE) model. The Bi-CPT module is designed for compact representations of cross-modal features, effectively eliminating spatial and modality redundancies at different granularity levels. In contrast to the traditional entropy models, our proposed Bi-CEE model not only achieves spatial-channel contextual adaptation through partitioning RGB and depth features but also incorporates information from other modalities as prior to enhance the accuracy of probability estimation for latent variables. Furthermore, this model enables parallel multi-stage processing to accelerate coding. Experimental results demonstrate the superiority of our proposed framework over the current compression scheme, outperforming both rate-distortion performance and downstream tasks, including surface reconstruction and semantic segmentation. The source code will be available at https://github.com/xyy7/Learning-based-RGB-D-Image-Compression .

Bidirectional transfer of a small membrane-impermeable molecule between the Caenorhabditis elegans intestine and germline

The extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) is a positive regulator of cell proliferation often upregulated in cancer. Its C. elegans ortholog MPK-1 stimulates germline stem cell (GSC) proliferation non-autonomously, from the intestine or somatic gonad. How MPK-1 can perform this task from either of these two tissues however remains unclear. We reasoned that somatic MPK-1 activity could lead to the generation of pro-proliferative small molecules that could transfer from the intestine and/or somatic gonad to the germline. Here, in support of this hypothesis, we demonstrate that a significant fraction of the small membrane-impermeable fluorescent molecule, 5-carboxyfluorescein (5-CF), transfers to the germline after its microinjection in the animal’s intestine. The larger part of this transfer targets oocytes and requires the germline RME-2 yolk receptor. A minor quantity of the dye is however distributed independently from RME-2 and more widely in the animal, including the distal germline, gonadal sheath, coelomocytes and hypodermis. We further show that the intestine-to-germline transfer efficiency of this RME-2 independent fraction does not vary together with GSC proliferation rates or MPK-1 activity. Therefore, if germline proliferation was influenced by small membrane-impermeable molecules generated in the intestine, it is unlikely that proliferation would be regulated at the level of molecule transfer rate. Finally, we show that conversely, a similar fraction of germline injected 5-CF transfers to the intestine, demonstrating transfer bidirectionality. Altogether, our results establish the possibility of an intestine-to-germline signaling axis mediated by small membrane-impermeable molecules that could promote GSC proliferation cell non-autonomously downstream of MPK-1 activity.

The Bidirectionality of Pragmatic Transfer in Chinese English Language Learners' Compliment Responses: The Effects of Second Language Proficiency

AbstractA handful of second language (L2) studies have explored bidirectional pragmatic transfer: forward pragmatic transfer—the influence of learners' first language (L1) on their L2—and reverse pragmatic transfer—the impact of learners' L2 on their L1. This explanatory sequential mixed‐methods study investigated how L2 proficiency influenced the bidirectionality of pragmatic transfer in compliment responses. Thirty‐four intermediate English‐as‐a‐foreign‐language (EFL) learners and 34 advanced EFL learners were recruited from a university in China. The results of computer‐mediated communication via WeChat showed that, similar to L1 Chinese speakers, the intermediate learners tended to deny compliments in English, indicating forward pragmatic transfer. Like L1 English speakers, the advanced learners frequently accepted compliments in Chinese, suggesting reverse pragmatic transfer. Furthermore, when responding to compliments in Chinese or English, some advanced learners preferred to accept compliments first and then deny them. Findings from interviews revealed that identity and language prestige might affect bidirectional pragmatic transfer.

Microbial community acclimation via polarity reversal supports extensive dechlorination and anaerobic mineralization of 2,4,6-trichlorophenol in biocathode

In the anaerobic biocathode, reductive dechlorination of 2,4,6-trichlorophenol (2,4,6-TCP) mainly proceeded to produce 4-monochlorophenol (4-MCP) and phenol, while anaerobic mineralization was challenging. In this study, biocathodes microbial communities were first acclimated via potentials repeatedly adjusted between −0.278 V and +0.200 V (T-200), −0.278 V and +0.400 V (T-400), and −0.278 V and +0.600 V (T-600). Subsequently, all biocathode potentials were stabilized at −0.278 V for the degradation of 2,4,6-TCP. The results revealed that the T-600 achieved the highest degradation rate of 2,4,6-TCP (0.43 d−1), outperforming T-200 (0.051 d−1), T-400 (0.020 d−1), and open-circuit bioreactor (OC, 0.038 d−1) groups. In T-600, pare-dechlorination was facilitated, allowing for the conversion of 2,4,6-TCP to 2-monochlorophenol (2-MCP). Additionally, the detection of 4-hydroxybenzoic acid, an anaerobic mineralization intermediate of 2,4,6-TCP, indicated that anaerobic mineralization was also occurring. Polarity reversal occurred only in T-600 during the acclimation period, resulting in alterations to the electrical properties of the biocathode and microbial community. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results indicated that there were more electroactive sites in biocathode of T-600, and the bidirectional extracellular electron transfer (EET) might be related to cytochrome. Mycobacterium (24.33% in slurry and 19.92% in biofilm), Thiobacillus (2.47% in slurry and 17.85% in biofilm), and Arenimonas (4.23% in slurry and 4.32% in cathode biofilm) were identified as the dominant electroactive bacteria in T-600, with Mycobacterium also playing an important role in the degradation of chlorophenols. These findings suggested that polarity reversal may represent a viable strategy for constructing microbial communities capable of achieving simultaneous dechlorination and mineralization of 2,4,6-TCP.

PPDistiller: Weakly-supervised 3D point cloud semantic segmentation framework via point-to-pixel distillation

Despite the significant growth in the availability of 3D light detection and ranging (LiDAR) point cloud data in recent years, annotation remains expensive and time-consuming. This has led to an increasing demand for weakly-supervised semantic segmentation (WSSS) methods in applications such as autonomous driving, mapping, and robotics. Existing approaches typically rely solely on LiDAR point cloud data for WSSS, which often results in lower segmentation accuracy due to the sparsity of point clouds. To address these challenges, we propose a novel architecture, PPDistiller, which employs multiple teacher networks from different modalities. Compared to other WSSS and multimodal approaches, PPDistiller achieves superior segmentation accuracy with fewer annotations. This is facilitated through the novel Mean Multi-Teacher Framework (MMT), which incorporates multiple modalities and teachers. To address the issue of lacking 2D labels, we propose the Distance-CAM Self-Training (DCAM-ST) module, which utilizes sparse 3D weak annotations to produce accurate 2D pixel-level annotations. To enable adaptive fusion of 2D and 3D data, we introduce the Attention Point to Pixel Fusion (APPF) module, facilitating bidirectional transfer of cross-modal knowledge. Additionally, to fully leverage the spatial semantic information in point cloud, we propose the Pyramid Semantic-context Neighbor Aggregation (PSNA) module, aiming to exploit spatial and semantic correlations to improve performance. Extensive experimentation on SemanticKITTI, ScribbleKITTI and nuScenes datasets demonstrates the superiority of our proposed method. Compared to state-of-the-art fusion and weakly-supervised methods, PPDistiller achieves the highest mean Intersection over Union (mIoU) scores under both fully-supervised and weakly-supervised settings.

A Cross-Modal Mutual Knowledge Distillation Framework for Alzheimer's Disease Diagnosis: Addressing Incomplete Modalities.

This paper was motivated by the challenge of early AD diagnosis, particularly in scenarios when clinicians encounter varied availability of patient imaging data, such as MRI and PET scans, often constrained by cost or accessibility issues. We propose an incomplete multimodal learning framework that produces tailored models for patients with only MRI and patients with both MRI and PET. This approach improves the accuracy and effectiveness of early AD diagnosis, especially when imaging resources are limited, via bi-directional knowledge transfer. We introduced a teacher model that prioritizes extracting common information between different modalities, significantly enhancing the student model's learning process. This paper includes theoretical analysis, simulation study, and real-world case study to illustrate the method's promising potential in early AD detection. However, practitioners should be mindful of the complexities involved in model tuning. Future work will focus on improving model interpretability and expanding its application. This includes developing methods to discover the key brain regions for predictions, enhancing clinical trust, and extending the framework to incorporate a broader range of imaging modalities, demographic information, and clinical data. These advancements aim to provide a more comprehensive view of patient health and improve diagnostic accuracy across various neurodegenerative diseases.

Zinc-modulated bidirectional copper transfer across the blood-brain barrier in a porcine brain capillary endothelial cell culture model system

The blood-brain barrier (BBB) serves as a crucial interface, regulating the transfer of trace elements (TEs) such as copper (Cu) and zinc (Zn) between the bloodstream and the brain. Cu and Zn are essential for maintaining neural function and enzymatic processes. Understanding the interplay of Cu and Zn with the BBB is crucial for elucidating their roles in neurological health and disease. This study investigates the bidirectional transfer of Cu across the BBB and examines the impact of Zn supplementation on this process using a porcine brain capillary endothelial cell (PBCEC) model. Transendothelial electrical resistance (TEER) and capacitance measurements confirmed barrier integrity upon TE exposure, while quantification of Cu and Zn concentrations via inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) in the culture medium provided essential baseline data. Transfer studies revealed significant increases in basolateral (brain side) Cu concentrations after apical (blood side) Cu incubation, with additional Zn supplementation reducing Cu transfer from apical to basolateral compartments. Conversely, Zn incubation showed no effect on basolateral-to-apical Cu transfer. Surprisingly, it was found that Cu also transferred significantly to the apical compartments when incubated basolaterally, and with slightly higher permeability coefficients than vice versa, indicating a potential role of PBCECs in regulating Cu transport both from blood to brain and from brain to blood. These findings suggest a bidirectional Cu trafficking across PBCECs, only slightly influenced unidirectionally by Zn supplementation, highlighting the intricate interplay between TEs at the BBB. Importantly, no alterations in barrier integrity were observed, underscoring the physiological relevance of the experimental conditions. Overall, this study sheds light on the complex dynamics of Cu and Zn transfer at the BBB, emphasizing the need for comprehensive investigations into TE interactions for a deeper understanding of brain TE homeostasis.

A Bidirectional Simultaneous Wireless Power and Data Transfer System with Non-Contact Slip Ring

A Bidirectional Simultaneous Wireless Power and Data Transfer System with Non-Contact Slip Ring

Vitamin E supplementation prevents obesogenic diet-induced developmental abnormalities in SR-B1 deficient embryos.

Genetic and environmental factors influence the risk of neural tube defects (NTD), congenital malformations characterized by abnormal brain and spine formation. Mouse embryos deficient in Scavenger Receptor Class B Type 1 (SR-B1), which is involved in the bidirectional transfer of lipids between lipoproteins and cells, exhibit a high prevalence of exencephaly, preventable by maternal vitamin E supplementation. SR-B1 knock-out (KO) embryos are severely deficient in vitamin E and show elevated reactive oxygen species levels during neurulation. We fed SR-B1 heterozygous female mice a high-fat/high-sugar (HFHS) diet and evaluated the vitamin E and oxidative status in dams and embryos from heterozygous intercrosses. We also determined the incidence of NTD. HFHS-fed SR-B1 HET females exhibited altered glucose metabolism and excess circulating lipids, along with a higher incidence of embryos with developmental delay and NTD. Vitamin E supplementation partially mitigated HFHS-induced maternal metabolic abnormalities and completely prevented embryonic malformations, likely through indirect mechanisms involving the reduction of oxidative stress and improved lipid handling by the parietal yolk sac.

GAP JUNCTION FUNCTION IS ESSENTIAL FOR SURVIVAL OF ACUTE LYMPHOBLASTIC LEUKEMIA CELLS.

Acute lymphoblastic leukemia has an intimate physical relationship with nonmalignant bone marrow stromal cells. We have recently demonstrated that stromal cells contribute to the survival of leukemia cells and that there is a bidirectional transfer of intracellular material between them. Understanding the mechanisms of stromal support of leukemia may provide insights into new therapies. To test the hypothesis that gap junctions are formed between acute lymphoblastic leukemia cells and nonmalignant stromal cells, and that gap junction function is essential for the survival of leukemia cells. We employed a well-characterized in vitro model of human bone marrow stromal cells and primary human B lymphoblastic leukemia cells and measured leukemia cell survival in coculture using flow cytometry. We measured the effects of gap junction antagonist peptides, carbenoxolone (a drug known to interfere with the gap junction function), and several leukemia chemotherapy drugs including methotrexate upon leukemia cell survival. We demonstrated that stromal cells need to be alive and metabolically active to keep leukemia cells alive. Physical contact between stromal and leukemia cells leads to an increase in gap junction proteins in leukemia cells. Gap junction inhibitory peptides impaired leukemia cell survival as did carbenoxolone, a nonpeptide inhibitor of the gap junction function. Stromal cell survival was not affected. We observed a very modest enhancement of methotrexate antileukemia activity by low-dose carbenoxolone but no significant interactions with dexamethasone, vincristine, mercaptopurine, or doxorubicin. These studies demonstrate that acute lymphoblastic cell survival is impaired by interference with the gap junction function. The development of drugs targeting gap junctions may provide a novel approach to the therapy of acute lymphoblastic leukemia.

Enhanced red UC emission of Er3+ ions by constructing multi-heterojunction core-shell nanoparticles

The construction of core-shell structures with multiple heterojunctions facilitates ion energy transfer and minimizes surface quenching effects, which are essential for enhancing and regulating the upconversion emission of materials. In this study, we effectively regulated the spatial distribution of Yb3+ and Er3+ ions in multilayered heterogeneous core-shell structures to significantly enhance the red upconversion emission of Er3+ ions. Specifically, the red emission intensity of the NaErF4@NaYbF4: 2 %Er3+@NaYF4 core-shell nanoparticles was enhanced nearly 24.4-fold compared to that of NaErF4 nanoparticles. This enhancement results from a bidirectional energy transfer process. Moreover, when we swapped the positions of the NaErF4 core and the NaYbF4: 2 %Er3+ shell and introduced NaYF4 inert isolation layer and Yb3+ ions, the red emission intensity of the NaYbF4:2 %Er3+@NaYF4:20 %Yb3+@NaErF4@ NaYF4 multilayer core-shell structure increased significantly by nearly 254.3-fold compared to NaErF4 nanoparticles. The remarkable enhancement of the red emission of Er3+ ions is primarily attributed to a well-organized bidirectional energy transfer process between the heavily doped core and shell Er3+-Yb3+ ion pairs. The energy transfer behavior of these multi-heterojunction core-shell nanoparticles was studied based on their spectral characteristics. The multilayer heterogeneous core-shell nanoparticles exhibited colorful emissions under different excitation conditions, highlighting their potential for biomedical applications and colorful anti-counterfeiting.

Mitochondrial Transfer Via Tunneling Nanotubes Between Mesenchymal Stem Cells and Retinal Pigment Epithelium In Vitro.

Mitochondrial transfer is a normal physiological phenomenon that occurs widely among various types of cells. In the study to date, the most important pathway for mitochondrial transport is through tunneling nanotubes (TNTs). There have been many studies reporting that mesenchymal stem cells (MSCs) can transfer mitochondria to other cells by TNTs. However, few studies have demonstrated the phenomenon of bidirectional mitochondrial transfer. Here, our protocol describes an experimental approach to study the phenomenon of mitochondrial transfer between MSCs and retinal pigment epithelial cells in vitro by two mitochondrial tracing methods. We co-cultured mito-GFP-transfected MSCs with mito-RFP-transfected ARPE19 cells (a retinal pigment epithelial cell line) for 24 h. Then, all cells were stained with phalloidin and imaged by confocal microscopy. We observed mitochondria with green fluorescence in ARPE19 cells and mitochondria with red fluorescence in MSCs, indicating that bidirectional mitochondrial transfer occurs between MSCs and ARPE19 cells. This phenomenon suggests that mitochondrial transport is a normal physiological phenomenon that also occurs between MSCs and ARPE19 cells, and mitochondrial transfer from MSCs to ARPE19 cells occurs much more frequently than vice versa. Our results indicate that MSCs can transfer mitochondria into retinal pigment epithelium, and similarly predict that MSCs can fulfill their therapeutic potential through mitochondrial transport in the retinal pigment epithelium in the future. Additionally, mitochondrial transfer from ARPE19 cells to MSCs remains to be further explored.