Analysis of the Nonequilibrium Phase Change Behaviors of the Cryoprotectant Solutions for Cryopreservation of Human Red Blood Cells with Low-Concentration Glycerol.

Recently, we proposed a low-glycerol cryoprotectant formulation (consisting of 0.4 M trehalose and 5% glycerol) for cryopreservation of human red blood cells (RBCs), which greatly reduced the concentration of glycerol, minimized intracellular ice damage, and achieved high recovery. Although this study was successful in cellular experiments, the nonequilibrium phase transition behaviors of the cryoprotective agent solution have not been systematically analyzed. Therefore, it is essential to provide reliable thermodynamic data to substantiate the viability of this cryopreservation technique. In this study, the phase change behaviors and thermal properties of typical trehalose and/or glycerol solutions quenched in liquid nitrogen were investigated using differential scanning calorimetry and cryomicroscopy. It was found that the glass transition temperatures of both the trehalose aqueous solution (<1.0 M) and glycerol aqueous solution (<40% w/v) did not vary apparently with the concentration at low concentrations, while they increased significantly with increasing concentration at high concentrations. Moreover, it was revealed that the inhibitory effect of trehalose on ice growth was affected by glycerol. We further found that the addition of low concentrations of glycerol facilitates the partial glass transition of trehalose solutions at low concentrations. The results of this work provide reliable thermodynamic data to support the cryopreservation of human RBCs with unusually low concentrations of glycerol.

Core-Shell Microfiber Encapsulation Enables Glycerol-Free Cryopreservation of RBCs with High Hematocrit.

Cryopreservation of red blood cells (RBCs) provides great potential benefits for providing transfusion timely in emergencies. High concentrations of glycerol (20% or 40%) are used for RBC cryopreservation in current clinical practice, which results in cytotoxicity and osmotic injuries that must be carefully controlled. However, existing studies on the low-glycerol cryopreservation of RBCs still suffer from the bottleneck of low hematocrit levels, which require relatively large storage space and an extra concentration process before transfusion, making it inconvenient (time-consuming, and also may cause injury and sample lose) for clinical applications. To this end, we develop a novel method for the glycerol-free cryopreservation of human RBCs with a high final hematocrit by using trehalose as the sole cryoprotectant to dehydrate RBCs and using core-shell alginate hydrogel microfibers to enhance heat transfer during cryopreservation. Different from previous studies, we achieve the cryopreservation of human RBCs at high hematocrit (> 40%) with high recovery (up to 95%). Additionally, the washed RBCs post-cryopreserved are proved to maintain their morphology, mechanics, and functional properties. This may provide a nontoxic, high-efficiency, and glycerol-free approach for RBC cryopreservation, along with potential clinical transfusion benefits.

Lung function and risk of incident dementia: A prospective cohort study of 431,834 individuals.

BACKGROUND: Whether lung function prospectively affects cognitive brain health independent of their overlapping factors remains largely unknown. This study aimed to investigate the longitudinal association between decreased lung function and cognitive brain health and to explore underlying biological and brain structural mechanisms. METHODS: This population-based cohort included 43,1834 non-demented participants with spirometry from the UK Biobank. Cox proportional hazard models were fitted to estimate the risk of incident dementia for individuals with low lung function. Mediation models were regressed to explore the underlying mechanisms driven by inflammatory markers, oxygen-carrying indices, metabolites, and brain structures. FINDINGS: During a follow-up of 3,736,181 person-years (mean follow-up 8.65 years), 5,622 participants (1.30 %) developed all-cause dementia, which consisted of 2,511 Alzheimer's dementia (AD) and 1,308 Vascular Dementia (VD) cases. Per unit decrease in lung function measure was each associated with increased risk for all-cause dementia (forced expiratory volume in 1 s [liter]: hazard ratio [HR, 95 %CI], 1.24 [1.14-1.34], P = 1.10 × 10-07; forced vital capacity [liter]: 1.16 [1.08-1.24], P = 2.04 × 10-05; peak expiratory flow [liter/min]: 1.0013 [1.0010-1.0017], P = 2.73 × 10-13). Low lung function generated similar hazard estimates for AD and VD risks. As underlying biological mechanisms, systematic inflammatory markers, oxygen-carrying indices, and specific metabolites mediated the effects of lung function on dementia risks. Besides, brain grey and white matter patterns mostly affected in dementia were substantially changed with lung function. INTERPRETATION: Life-course risk for incident dementia was modulated by individual lung function. Maintaining optimal lung function is useful for healthy aging and dementia prevention.

Microencapsulation and nanowarming enables vitrification cryopreservation of mouse preantral follicles.

Preantral follicles are often used as models for cryopreservation and in vitro culture due to their easy availability. As a promising approach for mammalian fertility preservation, vitrification of preantral follicles requires high concentrations of highly toxic penetrating cryoprotective agents (up to 6 M). Here, we accomplish low-concentration-penetrating cryoprotective agent (1.5 M) vitrification of mouse preantral follicles encapsulated in hydrogel by nanowarming. We find that compared with conventional water bath warming, the viability of preantral follicles is increased by 33%. Moreover, the cavity formation rate of preantral follicles after in vitro culture is comparable to the control group without vitrification. Furthermore, the percentage of MII oocytes developed from the vitrified follicles, and the birth rate of offspring following in vitro fertilization and embryo transfer are also similar to the control group. Our results provide a step towards nontoxic vitrification by utilizing the synergistic cryoprotection effect of microencapsulation and nanowarming.

Transmembrane Water Transport and Intracellular Ice Formation of Human Umbilical Vein Endothelial Cells During Freezing.

Long-term cryopreservation of human umbilical vein endothelial cells (HUVECs) is important and beneficial for a variety of biomedical research and applications. In this study, we investigated HUVEC's cryobiological characteristics and parameters that are indispensable for predicting and determining an optimal cooling rate to prevent lethal intracellular ice formation (IIF) and severe cell dehydration during the cryopreservation processes. The parameters include cell membrane hydraulic conductivity (i.e., cell membrane water permeability), Lp, cell membrane water permeability activation energy, Elp, and osmotically inactive volume of a cell Vb. Cryomicroscopy was used to study the IIF phenomena and cell volume excursion at various cooling rates, 1, 10, and 20°C/min, respectively, based on which the cryobiological parameters were determined using biophysical and mathematical models. Results from this research work laid an important cryobiological foundation for the optimization of HUVEC's cryopreservation conditions.

Label-Free and Noninvasive Single-Cell Characterization for the Viscoelastic Properties of Cryopreserved Human Red Blood Cells Using a Dielectrophoresis-On-a-Chip Approach.

Successful human red blood cell cryopreservation techniques have been gradually developed in recent decades, with great potential for use in clinical medicine and basic research. The mechanical properties of a single cell are important clues to reveal the physiological and pathological state of the red blood cell, but they have not been used to assess the physiological state of the cell after cryopreservation. Herein, we investigated the effects of cryopreservation processes on human red blood cell biomechanics by means of a microfluidic, label-free, synchronous, and nondestructive electrodeformation assay. We found that the effects of viscoelasticity of the red blood cell membrane between permeable and impermeable cryoprotectants were different. Our findings showed that high freeze-thaw recovery did not mean that the recovered cells had excellent viscoelasticity. The results demonstrate that single-cell viscoelasticity is an irreplaceable indicator for assessing the quality of the recovered cells and help us to deepen understanding of the cryoinjury mechanism. Assessment of the single cell viscoelasticity offers significant potential for application in optimizing the cryopreservation process and screening optimal cryoprotectants.

Hydrogel Microencapsulation Enhances Cryopreservation of Red Blood Cells with Trehalose.

Cryopreservation of red blood cells (RBCs) plays a vital role in preserving rare blood and serologic testing, which is essential for clinical transfusion medicine. The main difficulties of the current cryopreservation technique are the high glycerol concentration and the tedious deglycerolization procedure after thawing. In this study, we explored a microencapsulation method for cryopreservation. RBC-hydrogel microcapsules with a diameter of approximately 2.184 ± 0.061 mm were generated by an electrostatic spraying device. Then, 0.7 M trehalose was used as a cryoprotective agent (CPA), and microcapsules were adhered to a stainless steel grid for liquid nitrogen freezing. The results show that compared with the RBCs frozen by cryovials, the recovery of RBCs after microencapsulation is significantly improved, up to a maximum of more than 85%. Additionally, the washing process can be completed using only 0.9% NaCl. After washing, the RBCs maintained their morphology and adenosine 5'-triphosphate (ATP) levels and met clinical transfusion standards. The microencapsulation method provides a promising, referenceable, and more practical strategy for future clinical transfusion medicine.

Risk of seizures and subclinical epileptiform activity in patients with dementia: A systematic review and meta-analysis.

BACKGROUND: Seizures and subclinical epileptiform activity are common yet easily overlooked among demented patients. We aimed to investigate their epidemiological characteristics in patients with dementia from various aspects. METHODS: We retrieved relevant observational studies from PubMed and Embase Library until March 2021. Pooled estimate effects were calculated using random-effects models. This study is registered with PROSPERO, number CRD42020200949. RESULTS: Of the 19144 identified studies, 27 were eligible for inclusion. The pooled period prevalence rates of seizures were 4.86% (95%CI: 3.43-6.51%), 2.68% (95%CI: 2.13-3.28%), 2.81% (95%CI: 2.02-3.71%）and 7.13% (95%CI: 2.67-13.14%) among patients with Alzheimer's disease (AD), Dementia of Lewy Body (DLB), Frontotemporal dementia (FTD) and Vascular dementia (VaD), respectively. The pooled incidence rate of seizures was [8.4 (95%CI: 4.2-12.7) per 1000 person-years] in AD patients. And the pooled relative risk of seizures in patients with AD was 3.35 (95%CI: 2.69-4.19). Besides, the pooled cumulative incidence rate and prevalence rate of subclinical epileptiform activity among AD patients were [21.41% (95%CI: 0.001-63.60%)] and 9.73% (95%CI: 0.26-28.38%), respectively. CONCLUSIONS: The accurate rates of seizures and subclinical epileptiform activities in the four major dementia types are high. Besides, patients with AD are likely at a higher risk of seizures.

Social Isolation, Social Interaction, and Alzheimer's Disease: A Mendelian Randomization Study.

BACKGROUND: Social isolation and social interaction have been suggested to be associated with Alzheimer's disease. However, the causality cannot be unambiguously assessed as traditional epidemiological methods are easily subject to unmeasured confounders and potential bias. OBJECTIVE: To examine bidirectional relationships between social isolation, social interaction, and Alzheimer's disease using Mendelian randomization method for assessing potential causal inference. METHODS: This bidirectional two-sample Mendelian randomization study used independent genetic variants associated with social isolation and social interaction (n = 302,567-487,647), and Alzheimer's disease (n = 455,258). MR analyses were performed using the inverse-variance-weighted (IVW) as the main MR analytical method to estimate the causal effect. For sensitivity analyses, we applied weighted median, MR Egger to further assess the credibility of the causal effect. RESULTS: Of the five types of social engagement examined in our study, only one showed evidence of an association with the risk of Alzheimer's disease. Attendance at a gym or sports club (IVW OR per SD change: 0.670; 95% CI: 0.463-0.970; p = 0.034) was inversely associated with the risk of Alzheimer's disease. We also found that AD may reduce the attendance at religious group (IVW OR per SD change: 1.017; 95% CI: 1.005-1.030; p = 0.004). CONCLUSION: This study suggests that regular attendance at a gym or sports club is causally associated with reduced risk of Alzheimer's disease. Further studies are warranted to elucidate potential mechanisms.

Fine-tuned dehydration by trehalose enables the cryopreservation of RBCs with unusually low concentrations of glycerol.

The clinical transfusion of red blood cells (RBCs) has provided the greatest number of cryobiology applications in the case of rare blood groups and antibody problems, as well as civil and military disasters. The main technical difficulty with the current clinical technique is the removal of high concentration glycerol (20% or 40%) after thawing. Reducing the probability of intracellular ice formation (IIF) as well as preventing the solution effect are crucial to ensure RBCs avoid cryoinjury. Here, the non-permeating cryoprotectant trehalose was used to dehydrate RBCs before freezing. Furthermore, with the substitution of the low concentration glycerol (5% or 7.5%) for the intracellular remaining water, the bulk of RBCs were successfully cryopreserved to obtain a nearly 95% high survival rate with rapid cooling via EP tubes. Additionally, the washed RBCs after cryopreservation maintained their morphology, deformability, ATP, and 2-3 DPG levels, and all of them met the clinical standards for transfusion safety. Moreover, the whole addition and washing process was simple and easy to operate and could be completed within 30 min, which is crucial for emergency uses. This method will provide more potential for current clinical RBCs cryopreservation practices.

Water-transport and intracellular ice formation of human adipose-derived stem cells during freezing.

The key to optimizing the cryopreservation strategy of human adipose-derived stem cells (hADSCs) is to identify the biophysical characteristics during freezing. Systematic freezing experiments were conducted under a cryo-microscope system to investigate the cryoinjury mechanism for hADSCs at different cooling rates. By simultaneously fitting morphological change data to the water-transport equation at 5, 10 and 20 °C/min, the plasma membrane hydraulic conductivity, Lpg, and activation energy, ELp, were determined. Moreover, the optimal cooling rate was also predicted by using mathematical model methods. Additionally, the surface-catalyzed nucleation (SCN) parameters were calculated by fitting in numerical models, Ω0SCN and k0SCN were determined at cooling rates of 30, 45 and 60 °C/min. These results may provide potential application value for cryopreservation of hADSCs.

Hydrogel Microfiber Encapsulation Enhances Cryopreservation of Human Red Blood Cells with Low Concentrations of Glycerol.

Cryopreservation of red blood cells (RBCs) has been studied as a typical example of cryobiology methodology. To date, a mature and long-term cryopreservation process for RBCs has been developed, which has the weakness of complicated procedures due to high concentrations of glycerol (Gly). Therefore, it is still a research focus to find a new method for cryopreservation of RBCs to reduce the concentrations of cryoprotectants (CPAs). In this study, alginate hydrogels, which have been widely used in preservation research, were selected because of their advantages such as lower cost, cytocompatibility, and crosslinking occurring under mild conditions. With a variety of CPA solutions, the RBC recovery with the cryopreservation of RBCs and RBC-laden hydrogel microfibers was compared in different situations. It was found that hydrogel microfiber encapsulation enhances cryopreservation of human RBCs with low concentrations of CPAs. And Gly can be removed by washing directly with a 0.9% sodium chloride solution. This study validated the feasibility of cryopreservation of RBC-laden hydrogel microfibers. It may provide a new and evolving direction for reducing the concentrations of CPAs used in the preservation of RBCs.

Improvement of a Simple and Cost-Effective Passive Cooling Rate-Controlled Device for Cell/Tissue Cryopreservation.

The currently used commercial cooling-rate control device is the liquid nitrogen controlled rate freezer (LNF), which has some shortcomings such as high cost, high liquid nitrogen consumption, and potential operational risks in quality control. Based on thermophysical properties of new materials, we improved, manufactured, and optimized a reliable yet simple device named the "passive cooling rate-controlled device (PCD)" with real-time temperature tracing. In this study, using the improved PCD we cryopreserved human umbilical vein endothelial cells (HUVECs) and compared the results with a standard commercial CryoMed LNF. The temperature profiles and cooling rates of the HUVEC samples in a cryopreservation solution (with dimethyl sulfoxide [DMSO] in 10% v/v concentration) were measured and automatically recorded by the PCD during the controlled cooling process. This study and experimental results showed that the HUVEC survival rates after cryopreservation using the PCD have no significant difference from those using the CryoMed LNF and that the improved PCD is a user-friendly, reliable, and low-cost device to ensure an optimal slow cooling rate ranging from -0.5 to -1°C/min for the cryopreservation. Considering the advantages of low cost, durability, reliability, and no liquid nitrogen consumption for the cooling process, it is concluded that the PCD is an excellent controlled cooling device to achieve a desired optimal cooling rate for cell/tissue cryopreservation.

Redox homeostasis protects mitochondria through accelerating ROS conversion to enhance hypoxia resistance in cancer cells.

Mitochondria are the powerhouses of eukaryotic cells and the main source of reactive oxygen species (ROS) in hypoxic cells, participating in regulating redox homeostasis. The mechanism of tumor hypoxia tolerance, especially the role of mitochondria in tumor hypoxia resistance remains largely unknown. This study aimed to explore the role of mitochondria in tumor hypoxia resistance. We observed that glycolysis in hypoxic cancer cells was up-regulated more rapidly, with far lesser attenuation in aerobic oxidation, thus contributing to a more stable ATP/ADP ratio. In hypoxia, cancer cells rapidly convert hypoxia-induced O(2˙)(-) into H2O2. H2O2 is further decomposed by a relatively stronger antioxidant system, causing ROS levels to increase lesser compared to normal cells. The moderate ROS leads to an appropriate degree of autophagy, eliminating the damaged mitochondria and offering nutrients to promote mitochondria fusion, thus protects mitochondria and improves hypoxia tolerance in cancer. The functional mitochondria could enable tumor cells to flexibly switch between glycolysis and oxidative phosphorylation to meet the different physiological requirements during the hypoxia/re-oxygenation cycling of tumor growth.

A Novel Technique of Long-Segment Tracheal Repair With Extended Bronchial Flap of Right Upper and Main Bronchus Plus Tracheoplasty.

Long-segment tracheal resection and repair pose a great challenge. We present a successful case of long-segment tracheal defect repair with extended bronchial flap of the right upper and main bronchus, together with a tracheoplastic method. This is a novel technique for repairing a large tracheal defect with an extended pedicled bronchial flap in specific situations.

Effect of hydroxyapatite nanoparticles on osmotic responses of pig iliac endothelial cells.

In order to fully explore the potential applications of nanoparticles in biopreservation, it is necessary to study the effect of nanoparticles on cell membrane permeabilities. The aim of this study is therefore to comparatively evaluate the osmotic responses of pig iliac endothelial cells in the absence and presence of commercially available hydroxyapatite nanoparticles. The results indicate that, after the introduction of 0.0 1 wt% hydroxyapatite nanoparticles, the dependence of cell membrane hydraulic conductivity (Lp) on temperature still obeys the Arrhenius relationship, while the reference value of the hydraulic conductivity of the cell membrane at 273.15K (Lpg) and the activation energy for water transport across cell membrane (ELp) change from 0.77 × 10(-14)m/Pa/s and 15.65 kJ/mol to 0.65 × 10(-14)m/Pa/s and 26.14 kJ/mol. That is to say, the reference value of the hydraulic conductivity of the cell membrane has been slightly decreased while the activation energy for water transport across cell membrane has been greatly enhanced, and thus it implies that the hydraulic conductivity of cell membrane are more sensitive to temperature in the presence of nanoparticles. These findings are of potential significance to the optimization of nanoparticles-aided cryopreservation.

Identifying the proton transfer reaction mechanism via a proton-bound dimeric intermediate for esomeprazoles by a kinetic method combined with density functional theory calculations.

RATIONALE: Esomeprazole analogs are a class of important proton pump inhibitors for the treatment of gastro-esophageal reflux diseases. Understanding the fragmentation reaction mechanism of the protonated esomeprazole analogs will facilitate the characterization of their complex metabolic fate in humans. In this paper, the kinetic method and theoretical calculations were applied to evaluate the fragmentation of protonated esomeprazole analogs. METHODS: All collision-induced dissociation (CID) mass spectrometry experiments were carried out using electrospray ionization (ESI) ion trap mass spectrometry in positive ion mode. Also the accurate masses of fragments were measured on by ESI quadrupole time-of-flight (QTOF) MS in positive ion mode. Theoretical calculations were carried out by the density functional theory (DFT) method with the 6-31G(d) basis set in the Gaussian 03 program. RESULTS: In the fragmentation of the protonated esomeprazole analogs, C-S bond breakage is observed, which gives rise to protonated 2-(sulfinylmethylene)pyridines and protonated benzimidazoles. DFT calculations demonstrate that the nitrogen atom of the pyridine part is the thermodynamically most favorable protonation site, and the C-S bond cleavage is triggered by the transfer of this ionizing proton from the nitrogen atom of the pyridine part to the carbon atom of the benzimidazole part to which the sulfinyl is attached. Moreover, with the kinetic plot, the intensity ratios of two protonated product ions yield a linear relationship with the differences in proton affinities of the corresponding neutral molecules, which provides strong experimental evidence that the reaction proceeds via proton-bound 2-(sulfinylmethylene)pyridine/benzimidazole complex intermediates. CONCLUSIONS: The kinetic method combined with theoretical calculations was successfully applied to probe the proton transfer reaction by proton-bound 2-(sulfinylmethylene)pyridine/benzimidazole complexes in the fragmentation of protonated esomeprazole analogs by ESI CID MS, which is a strong evidence that the kinetic method can be applied in identifying a proton-bound dimeric intermediate in the fragmentation of protonated ions.

Ultrasound-assisted magnetic solid-phase extraction based ionic liquid-coated Fe3O4@graphene for the determination of nitrobenzene compounds in environmental water samples.

An ultrasound-assisted magnetic solid-phase extraction procedure with the [C7MIM][PF6] ionic liquid-coated Fe3O4-grafted graphene nanocomposite as the magnetic adsorbent has been developed for the determination of five nitrobenzene compounds (NBs) in environmental water samples, in combination with high performance liquid chromatography-photodiode array detector (HPLC-PDA). Several significant factors that affect the extraction efficiency, such as the types of magnetic nanoparticle and ionic liquid, the volume of ionic liquid and the amount of magnetic nanoparticles, extraction time, ionic strength, and solution pH, were investigated. With the assistance of ultrasound, adsorbing nitrobenzene compounds by ionic liquid and self-aggregating ionic liquid onto the surface of the Fe3O4-grafted graphene proceeded synchronously, which made the extraction achieved the maximum within 20 min using only 144 µL [C7MIM][PF6] and 3 mg Fe3O4-grafted graphene. Under the optimized conditions, satisfactory linearities were obtained for all NBs with correlation coefficients larger than 0.9990. The mean recoveries at two spiked levels ranged from 80.35 to 102.77%. Attributed to the convenient magnetic separation, the Fe3O4-grafted graphene could be recycled many times. The proposed method was demonstrated to be feasible, simple, solvent-saving and easy to operate for the trace analysis of NBs in environmental water samples.

Ultrasound-assisted magnetic SPE based on Fe3O4-grafted graphene for the determination of polychlorinated biphenyls in water samples.

An ultrasound-assisted magnetic SPE procedure with an Fe3 O4 -grafted graphene nanocomposite as the magnetic adsorbent has been developed to determine seven polychlorinated biphenyls (PCBs; PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, and PCB180) simultaneously in 200 mL environmental water samples, in combination with GC-MS/MS. Several factors related to magnetic SPE efficiencies, such as the superparamagnetic intensity and amount of adsorbent, extraction time, sample pH, and desorption conditions were investigated. With the assistance of ultrasound, the extraction achieved the maximum within only 20 s, attributed to the powerful adsorptive ability of the magnetic adsorbent toward the PCBs. Under the optimized conditions, an excellent linearity was observed in the range of 0.1-100 ng/L for PCB28, 0.2-100 ng/L for PCB52, and 0.5-100 ng/L for the other five PCBs with the correlation coefficients ranging from 0.9988 to 0.9996. The mean recoveries at spiked levels of 5.0 and 10.0 ng/L were 84.9-108.5%, the coefficients of variations were <6.5%. With convenient magnetic separation, the synthesized magnetic adsorbent could be recycled more than ten times. The proposed method was demonstrated to be feasible, simple, rapid, and easy to operate for the trace analysis of the PCBs in environmental water samples.

Single electron redox via an ion-neutral complex in the fragmentation of protonated benzoylferrocenes.

RATIONALE: Ferrocene derivatives have become very popular molecules for biological applications. Although considerable experimental and theoretical calculation studies have demonstrated that ferrocene derivatives are easily oxidized during electrospray ionization (ESI), the details of the single electron redox reaction for protonated benzoylferrocenes in collision-induced dissociation (CID) mass spectrometry (MS) has not been obtained. Characterizing this mechanism is useful for further understanding the properties of ferrocene-containing biomaterials. METHODS: All CID MS experiments were carried out using ESI ion trap mass spectrometry in positive ion mode. In addition, the accurate mass of fragments was measured on a ESI quadrupole time-of-flight (QTOF) mass spectrometer in positive ion mode. Theoretical calculations were carried out by the density functional theory (DFT) method with a hybrid basis set consisting of 6-31G (d) and ECP LanL2DZ in the Gaussian 03 program. RESULTS: In the fragmentation of protonated benzoylferrocenes, the characterized ferrocinium cation was observed, which was proposed from the cleavage of the bond between the ipso-carbon atom and the carbonyl carbon followed by a single electron redox in [substituted benzoyl/ferrocene] complexes. Moreover, when the complex contained an oxidant (substituted benzoyl cation) with higher electron affinity, the single electron redox reaction was more efficient. A correlation was established between the intensities of the two competitive product ions and the electron affinities of substituted benzoyl cations. CONCLUSIONS: The single electron redox reaction by the [substituted benzoyl/ferrocene] complexes was proposed by CID MS and theoretical calculations, which provided potential evidence to further understand the reversible reduction characteristics of ferrocene-containing biomaterials.