Concentration Gradient Research Articles

Repurposing discarded leukodepletion filters as a source of mononuclear cells for advanced in vitro research

In light of advancements in the field of immuno-oncology, the demand for obtaining mononuclear cells for in vitro assays has surged. However, obtaining these cells from healthy donors remains a challenging task due to difficulties in donor recruitment and the requirement for substantial blood volumes. Here, we present a protocol for isolating peripheral blood mononuclear cells (PBMCs) from leukodepletion filters used in whole blood and erythrocytes by apheresis donations at the Hemonucleus of the Barretos Cancer Hospital, Brazil. The method involves rinsing the leukodepletion filters and subsequent centrifugation using a Ficoll-Paque concentration gradient. The isolated PBMCs were analyzed by flow cytometry, which allowed the identification of various subpopulations, including CD4+ T lymphocytes (CD45+CD4+), CD8+ T lymphocytes (CD45+CD8+), B lymphocytes (CD45+CD20+CD19+), non-classical monocytes (CD45+CD64+CD14−), classical monocytes (CD45+CD64+CD14+), and granulocytes (CD45+CD15+CD14−). In our comparative analysis of filters, we observed a higher yield of PBMCs from whole blood filters than those obtained from erythrocytes through apheresis. Additionally, fresh samples exhibited superior viability when compared to cryopreserved ones. Given this, leukodepletion filters provide a practical and cost-effective means to isolate large quantities of pure PBMCs, making it a feasible source for obtaining mononuclear cells for in vitro experiments. SummaryHere, we provide a detailed protocol for the isolation of mononuclear cells from leukodepletion filters, which are routinely discarded at the Barretos Cancer Hospital's Hemonucleus.

What drives the heterogeneous interdiffusion in the Li-Si interfacial region of Si anodes: the Li flux or the Si flux?

The electrochemical reaction in silicon (Si) electrode, accompanying with tremendous volume expansion, causes rapid capacity fade of Li-ion batteries. The Li-ion concentration gradient and structural distribution uniformity influence the inhomogeneous expansion, and the kinetic mechanism of lithiation and interfacial morphology evolvement remains debated. The present study focuses on the dynamics of Li-Si interdiffusion at Si/Li interfaces with various Si-facet orientations and phases using a machine-learning potential. We find that the Si flux from bulk Si to Li-Si interface regions controls the length of Li-Si interdiffusion region. The lithiation length in different Si/Li interface systems exhibits the order of amorphous-Si > crystalline-Si(110) > crystalline-Si(100) > crystalline-Si(111), which agrees with the experimental trend. Our atomic simulations further reveal that the key factor determining the Li-Si interdiffusion is the difference of on-site Si atomic energies between the bulk Si and the Li-Si interface regions. We propose that the large interdiffusion extent is due to a low thermodynamics barrier. Our findings provide insights for the development of high-performance Si anode materials.

Uni-directional release of ibuprofen from an asymmetric fibrous membrane enables effective peritendinous anti-adhesion

Drug-loaded porous membranes have been deemed to be effective physicochemical barriers to separate postoperative adhesion-prone tissues in tendon healing. However, cell viability and subsequent tissue regeneration might be severely interfered with the unrestricted release and the locally excessive concentration of anti-inflammatory drugs. Herein, we report a double-layered membrane with sustained and uni-directional drug delivery features to prevent peritendinous adhesion without hampering the healing outcome. A vortex-assisted electrospinning system in combination with ibuprofen (IBU)-in-water emulsion was utilized to fabricate IBU-loaded poly-ʟ-lactic-acid (PLLA) fiber bundle membrane (PFB-IBU) as the anti-adhesion layer. The resultant highly porous structure, oleophilic and hydrophobic nature of PLLA fibers enabled in situ loading of IBU with a concentration gradient across the membrane thickness. Aligned collagen nanofibers were further deposited at the low IBU concentration side of the membrane for regulating cell growth and achieving uni-directional release of IBU. Drug release kinetics showed that the release amount of IBU from the high concentration side reached 79.32% at 14 d, while it was only 0.35% at the collagen side. Therefore, fibroblast proliferation at the high concentration side was successfully inhibited without affecting the oriented growth of tendon-derived stem cells at the other side. In vivo evaluation of the rat Achilles adhesion model confirmed the successful peritendinous anti-adhesion of our double-layered membrane, in that the macrophage recruitment, the inflammatory factor secretion and the deposition of pathological adhesion markers such as α-SMA and COL-III were all inhibited, which greatly improved the peritendinous fibrosis and restored the motor function of tendon.

An optofluidic system for the concentration gradient screening of oocyte protection drugs

Oocytes protective drug screening is essential for the treatment of reproductive diseases. However, few studies construct the oocyte in vitro drug screening microfluidic systems because of their enormous size, scarcity, and sensitivity to the culture environment. Here, we present an optofluidic system for oocyte drug screening and state analysis. The system consists of two parts: an open-top drug screening microfluidic chip and an optical Fourier filter analysis part. The open-top microfluidic chip anchors single oocyte with hydrogel and allows nutrient and gas environment updating which is essential for oocyte culturing. The optical filter analysis part is used to accurately analyse the status of oocytes. Based on this system, we found that fluorene-9-bisphenol (BHPF) damaged the oocyte spindle in a dose-dependent manner, a high dose of melatonin (10−3 M) effectively reduces the percentage of abnormally arranged chromosomes of oocytes exposed to 40 μM BHPF. This optofluidic system shows great promise for the culture of oocytes and demonstrates the robust ability for convenient multi-concentration oocytes drug screening. This technology may benefit further biomedicine and reproductive toxicology applications in the lab on a chip community.

Numerical simulations of energy storage performance in a close configuration: A Galerkin finite element-based computation

The energy storage features on natural convection in Casson fluids are investigated in this work using the finite element method. By measuring cylinders and wavy surfaces, we may examine flow patterns and the effectiveness of heat transmission systems. We study the variation of the mass and heat transfer rates as a function of the cylinder geometry. To approximately determine velocities and temperatures, the Ladyzhenskaya-Babuška—Brezzi (LBB)-stable element is employed. Following this discretization, the resulting discrete nonlinear system is linearized using Newton's method and subsequently solved using PARDISO. Fractional applications in Casson fluid analysis reveal insights into energy storage effects, employing finite element methods to explore flow patterns, heat transmission efficiency, and geometric variations while observing the impact of parameters such as Rayleigh, Hartmann, and Lewis numbers on fluid behavior and thermal properties. The preceding research has verified the accuracy of the numerical results. According to the results, concentration gradients and other modifications to liquids become more noticeable as the Rayleigh number grows. Convective heat transmission is reduced as the Ha is raised. When the Le grows, the deformation Nuavg and Shavgalso increase. Reducing the beta makes the isotherms more stable and less affected by the motion of the fluid.

Establishing mainstream partial nitrification in the membrane aerated biofilm reactor by limiting the oxygen concentration in the biofilm

The proliferation of nitrite oxidizing bacteria (NOB) still remains as a major challenge for nitrogen removal in mainstream wastewater treatment process based on partial nitrification (PN). This study investigated different operational conditions to establish mainstream PN for the fast start-up of membrane aerated biofilm reactor (MABR) systems. Different oxygen controlling strategies were adopted by employing different influent NH4+-N loads and oxygen supply strategies to inhibit NOB. We indicated the essential for NOB suppression was to reduce the oxygen concentration of the inner biofilm and the thickness of aerobic biofilm. A higher NH4+-N load (7.4 g-N/(m2·d)) induced higher oxygen utilization rate (14.4 g-O2/(m2·d)) and steeper gradient of oxygen concentration, which reduced the thickness of aerobic biofilm. Employing closed-end oxygen supply mode exhibited the minimum concentration of oxygen to realize PN, which was over 46% reduction of the normal open-end oxygen mode. Under the conditions of high NH4+-N load and closed-end oxygen supply mode, the microbial community exhibited a comparative advantage of ammonium oxidizing bacteria over NOB in the aerobic biofilm, with a relative abundance of Nitrosomonas of 30–40% and no detection of Nitrospira. The optimal fast start-up strategy was proposed with open-end aeration mode in the first 10 days and closed-end mode subsequently under high NH4+-N load. The results revealed the mechanism of NOB inhibition on the biofilm and provided strategies for a quick start-up and stable mainstream PN simultaneously, which poses great significance for the future application of MABR.

A sensitive system based on radon amplification at soil-air interface: Aiming to advance earthquake precursor research

Radon, a natural radioactive gas, serves as a valuable tracer in geophysical research and atmospheric science such as detecting stress induced signal in bedrock. However, the conventional radon monitoring methods often lack the sensitivity required to accurately capture such signals. This limitation, coupled with interference from meteorological effects, poses challenges in distinguishing genuine stress-induced signals. In this study, we propose a novel approach utilizing radon concentration gradients at the soil-air interface to enhance sensitivity and detect stress induced radon signals more effectively. Drawing from pressure diffusion models, we demonstrate how seismic stress accumulation in bedrock alters radon profiles in the sub-soil, providing insights into the mechanisms underlying stress-induced radon variations. Building upon this theoretical framework, we introduce the “Bhabha Radon Observatory for Seismic Application (BhaROSA)," a remote sensing, solar-powered radon observatory designed for widespread deployment and continuous unattended monitoring for big database generation. Field experiments comparing BhaROSA's performance to conventional soil probe techniques validate and confirm the superior sensitivity in line with theoretical predictions. This innovative approach holds promise for improving our understanding of stress dynamics in bedrock and has potential applications in various geophysical and atmospheric science such as earthquake precursory research, geo-genic radon potential and risk assessment. To progress, we propose international alliance and application of deep learning to a big database of precursor signals, which may lead to more informed conclusions on earthquake predictability-an enduring and unsolved challenge for humanity.

Methane plume detection after the 2022 Nord Stream pipeline explosion in the Baltic Sea

On September 26th, 2022, the detonations at the gas pipelines Nord Stream 1 and 2 resulted in some of the largest non-natural releases of methane known. The distribution of methane in the surrounding seawater and the possible effects were not apparent. To trace the pathways of methane we recorded CH4 concentrations and the isotopic signal (δ13C-CH4) in seawater, and air. A week post-explosion, we detected methane concentrations up to 4 orders of magnitude above the natural Baltic Sea background. The released fossil methane created a distinct plume with δ13C-CH4 ratios differing from natural background values. The strong water stratification preserved the distribution pattern initiated by the explosion, shown by the laterally strong concentration gradient within the plume. Our analysis encompasses three stages of the explosion's impact; the initial sea-air methane release, measurements taken during our research expedition one week later, and a third stage triggered by the shift from summer to winter conditions as an outlook on how winter mixing and microbial activity will influence the plume.

Optimizing Nanofluidic Energy Harvesting in Synthetic Clay-based Membranes by Annealing Treatment.

Nanofluidic energy harvesting from salinity gradients is studied in 2D nanomaterials-based membranes with promising performance as high ion selectivity and fast ion transport. In addition, moving forward to scalable, feasible systems requires environmentally friendly materials to make the application sustainable. Clay-based membranes are attractive for being environmentally friendly, non-hazardous, and easy to manipulate materials. However, achieving underwater stability for clay-based membranes remains challenging. In this work, the synthetic clay Laponite is used to prepare clay-based membranes with high stability and excellent performance for osmotic energy harvesting. The Laponite membranes (Lap-membranes) are stabilized by low-temperature annealing treatment to effectively reduce the interlayer space, achieving a continuous operation under salinity gradients. Furthermore, the Lap-membranes conserve integrity while soaking in water for more than one month. The output power density improves from ≈4.97W m-2 on the pristine membrane to ≈9.89W m-2 in the membrane treated 12 h at 300°C from a 30-fold concentration gradient. Especially, It is found that the presence of interlayer water to be favorable for ion transport. Different mechanisms are proposed in the Lap-membranes involved for efficient ion selectivity and the states found with varying annealing temperatures. This work demonstrates the potential application of Laponite based nanomaterials for nanofluidic energy harvesting.

Large-area, self-healing block copolymer membranes for energy conversion

Membranes are widely used for separation processes in applications such as water desalination, batteries and dialysis, and are crucial in key sectors of our economy and society1. The majority of technologically exploited membranes are based on solid polymers and function as passive barriers, whose transport characteristics are governed by their chemical composition and nanostructure. Although such membranes are ubiquitous, it has proved challenging to maximize selectivity and permeability independently, leading to trade-offs between these pertinent characteristics2. Self-assembled biological membranes, in which barrier and transport functions are decoupled3,4, provide the inspiration to address this problem5,6. Here we introduce a self-assembly strategy that uses the interface of an aqueous two-phase system to template and stabilize molecularly thin (approximately 35 nm) biomimetic block copolymer bilayers of scalable area that can exceed 10 cm2 without defects. These membranes are self-healing, and their barrier function against the passage of ions (specific resistance of approximately 1 MΩ cm2) approaches that of phospholipid membranes. The fluidity of these membranes enables straightforward functionalization with molecular carriers that shuttle potassium ions down a concentration gradient with exquisite selectivity over sodium ions. This ion selectivity enables the generation of electric power from equimolar solutions of NaCl and KCl in devices that mimic the electric organ of electric rays.

Influence of heat flow due to concentration gradient on unsteady MHD heat and mass transform dissipative flow with spanwise fluctuating temperature

This study investigates the influence of heat flow due to a concentration gradient on unsteady Newtonian free convective magnetohydrodynamic heat and mass transform dissipative fluid flow over a heated normal porous plate in the presence of radiation absorption and chemical reaction. The plate temperature is assumed to fluctuate in a spanwise cosinusoidal manner over a time and exhibit heat generation with suction velocity. The analysis employs the multiple regular perturbation method to evaluate the governing equations under stipulated boundary conditions. The outcomes are visually depicted to assess the impact of various parameters on the system dynamics. Graphical representations illustrate the physical significance of various parameters on velocity, temperature, and concentration. Additionally, skin friction, mass transfer rate, and heat transfer coefficients are presented in tabular form. The significant findings indicate that velocity, temperature, and skin friction are directly proportional to parameters such as radiation absorption, heat generation, and heat flux due to a chemical potential gradient, whereas Sherwood and concentration are inversely proportional to the Schmidt number and chemical reaction. The outcomes obtained in this study have been cross-referenced with existing scientific literature, demonstrating strong concordance. This alignment provides confidence in the numerical results.

Diffusiophoresis in Polymer and Nanoparticle Gradients.

Diffusiophoresis is the movement of the colloidal particles in response to a concentration gradient and can be observed for both electrolyte (e.g., salt) and nonelectrolyte (e.g., glucose) solutes. Here, we investigated the diffusiophoretic behavior of polystyrene (PS-carboxylate surface) microparticles in nonadsorbing charged and uncharged solute gradients [sodium polystyrenesulfonate (NaPSS), polyethylene glycol (PEG), and nanoscale colloidal silica (SiO2)] using a dead-end channel setup. We compared the diffusiophoretic motion in these gradient types with each other and to the case of using a monovalent salt gradient. In each of the nonadsorbing gradient systems (NaPSS, PEG, and SiO2 nanoparticles), the PS particles migrated toward the lower solute concentration. The exclusion distance values (from the initial position) of particles were recorded within the dead-end channel, and it was found that an increase in solute concentration increases exclusion from the main channel. In the polyelectrolyte case, the motion of PS microparticles was reduced by the addition of a background salt due to reduced electrostatic interaction, whereas it remained constant when using the neutral polymer. Particle diffusiophoresis in gradients of polyelectrolytes (charged macromolecules) is quite similar to the behavior when using a PEG gradient (uncharged macromolecule) in the presence of a background electrolyte. Moreover, we observed PS microparticles under different concentrations and molecular weights of PEG gradients. By combining the simulations, we estimated the exclusion length, which was previously proposed to be the order of the polymer radius. Furthermore, the movement of PS microparticles was analyzed in the gradient of silica nanoparticles. The exclusion distance was higher in silica nanoparticle gradients compared to similar-size PEG gradients because silica nanoparticles are charged. The diffusiophoretic transport of the PS microparticles could be simulated by considering the interaction between the PS microparticles and silica nanoparticles.

A Reverse Nonequilibrium Molecular Dynamics Algorithm for Coupled Mass and Heat Transport in Mixtures.

We present a new method for introducing stable nonequilibrium concentration gradients in molecular dynamics simulations of mixtures. This method extends earlier reverse nonequilibrium molecular dynamics (RNEMD) methods, which use kinetic energy scaling moves to create temperature or velocity gradients. In the new scaled particle flux (SPF-RNEMD) algorithm, energies and forces are computed simultaneously for a molecule existing in two nonadjacent regions of a simulation box, and the system evolves under a linear combination of these interactions. A continuously increasing particle scaling variable is responsible for the migration of the molecule between the regions as the simulation progresses, allowing for simulations under an applied particle flux. To test the method, we investigate diffusivity in mixtures of identical but distinguishable particles and in a simple mixture of multiple Lennard-Jones particles. The resulting concentration gradients provide Fick diffusion constants for mixtures. We also discuss using the new method to obtain coupled transport properties using simultaneous particle and thermal fluxes to compute the temperature dependence of the diffusion coefficient and activation energies for diffusion from a single simulation. Lastly, we demonstrate the use of this new method in interfacial systems by computing the diffusive permeability of a molecular fluid moving through a nanoporous graphene membrane.

Shear viscosity of a near-critical binary system analyzed with variable-temperature atomic force microscopy

Variation in shear viscous drag in a near-critical binary mixture was measured between a hydrophilic probe sphere and a hydrophilic substrate down to a distance range comparable to or smaller than the correlation length ξ using a magnetic excitation method of atomic force microscopy at temperatures T=Tc−∆T with ∆T varying from 0.1 to 0.7 K. As the temperature approached the Tc, the increase in the drag coefficient toward the zero distance was observed to be less pronounced in the distance range below ca. 100 nm. The data was discussed as arising from suppression in a concentration gradient in the intersurface region due to the overlap of the affected layers on similar surfaces.

Proton-driven sodium secretion in a saline water animal

Aquatic animals residing in saline habitats either allow extracellular sodium concentration to conform to environmental values or regulate sodium to lower levels. The latter strategy requires an energy-driven process to move sodium against a large concentration gradient to eliminate excess sodium that diffuses into the animal. Previous studies of invertebrate and vertebrate species indicate a sodium pump, Na+/K+ ATPase, powers sodium secretion. We provide the first functional evidence of a saline-water animal, Aedes taeniorhynchus mosquito larva, utilizing a proton pump to power this process. Vacuolar-type H+ ATPase (VHA) protein is highly expressed on the apical membrane of the posterior rectal cells, and in situ sodium flux across this epithelium increases significantly in larvae held in higher salinity and is sensitive to Bafilomycin A1, an inhibitor of VHA. We also report the first evidence of splice variants of the sodium/proton exchanger, NHE3, with both high and low molecular weight variants highly expressed on the apical membrane of the posterior rectal cells. Evidence of NHE3 function was indicated with in situ sodium transport significantly inhibited by a NHE3 antagonist, S3226. We propose that the outward proton pumping by VHA establishes a favourable electromotive gradient to drive sodium secretion via NHE3 thus producing a hyperosmotic, sodium-rich urine. This H+- driven Na+ secretion process is the primary mechanism of ion regulation in salt-tolerant culicine mosquito species and was first investigated over 80 years ago.

Reduced internal stress of quasi-single crystalline Na4Fe3(PO4)2P2O7 electrode enhancing sodium-ion kinetics

A NASICON-type quasi-single crystalline Na4Fe3(PO4)2P2O7 (SC) cathode material was successfully synthesized via a freeze-drying method. The as-optimized SC sample displays both outstanding rate performance (107.9 and 88.5 mAhg−1 at 0.1C and 5C, respectively) and excellent cycling stability (88.1 % of capacity retention after 1000 cycles at 1C). Reduced sodium ion migration path of as-prepared SC cathode material effectively enhanced the kinetics of Na+ upon cycling. More importantly, the SC structure could suppress nearly 50 % of internal strain, prodigiously reducing the local stress accumulation accompanied by the inhomogeneous sodium concentration gradient during the charging/discharging processes. The smaller the stress accumulation, the more stable the crystal structure would be obtained, which maintained a more superb mechanical stability of the SC cathode material. At the same time, a high-spin state of Fe in the SC sample was confirmed by both of electron paramagnetic resonance and temperature-dependent magnetization susceptibility, indicating that the eg orbital occupation of Fe2+ could be regulated to optimize the bond strength between the reduction and oxidation processes. As a consequence, the band gap of SC material has decreased from 1.66 to 1.45 eV, and the electronic conductivity has increased from 6.0 to 32.4 μS/cm. It is believed that the SC cathode material could be a competitive candidate material for sodium ion batteries.

Diffusiophoresis of a Charged Soft Sphere in a Charged Spherical Cavity

The quasi-steady diffusiophoresis of a soft particle composed of an uncharged hard sphere core and a uniformly charged porous surface layer in a concentric charged spherical cavity full of a symmetric electrolyte solution with a concentration gradient is analyzed. By using a regular perturbation method with small fixed charge densities of the soft particle and cavity wall, the linearized electrokinetic equations relevant to the fluid velocity field, electric potential profile, and ionic concentration distributions are solved. A closed-form formula for the diffusiophoretic (electrophoretic and chemiphoretic) velocity of the soft particle is obtained as a function of the ratios of the core-to-particle radii, particle-to-cavity radii, particle radius to the Debye screening length, and particle radius to the permeation length in the porous layer. In typical cases, the confining charged cavity wall significantly influences the diffusiophoresis of the soft particle. The fluid flow caused by the diffusioosmosis (electroosmosis and chemiosmosis) along the cavity wall can considerably change the diffusiophoretic velocity of the particle and even reverse its direction. In general, the diffusiophoretic velocity decreases with increasing core-to-particle radius ratios, particle-to-cavity radius ratios, and the ratio of the particle radius to the permeation length in the porous layer, but increases with increasing ratios of the particle radius to the Debye length.

Boosting interface compatibility of high-voltage LiNi0.5Mn1.5O4 cathode materials with an ionic-conductive Li0.33La0.56TiO3 coating

High voltage LiNi0.5Mn1.5O4 (LNMO) is a crucial cathode material for lithium-ion batteries (LIBs) aiming at high energy densities. However, its performance is hindered by the dissolution of transition metal ions and the instability of the cathode electrolyte interface (CEI) film at elevated voltages. To address these issues, we report a solvothermal method to prepare LNMO coated with Li+-conductor Li0.33La0.56TiO3 (LNMO@LLTO). Our study reveals that the LLTO coating not only enhances ion diffusion at the interface, minimizing the Li+ concentration gradient, and acts as a barrier against Mn-ion dissolution. This coating minimizes side reactions, mitigates structural degradation, and promotes the formation of a stable and balanced CEI film that incorporates LLTO, thus ensuring the long-term cycle stability. When compared to bulk LNMO, the LNMO@LLTO cathode demonstrates superior performance, maintaining reversible capacities of 111.4 and 102.2 mAh·g−1 after 500 cycles at 2 and 5C at 25 °C, respectively. Even at 60 °C, the LNMO@LLTO maintains a high capacity of 94.3 mAh·g−1 with minimal electrochemical polarization after 200 cycles at 2C. This simple preparation technique, together with its performance promotion, offers new insights into the development of high voltage cathode materials for high energy density LIBs.

Mapping the membrane orientation of auxin homeostasis regulators PIN5 and PIN8 in Arabidopsis thaliana root cells reveals their divergent topology.

PIN proteins establish the auxin concentration gradient, which coordinates plant growth. PIN1-4 and 7 localized at the plasma membrane (PM) and facilitate polar auxin transport while the endoplasmic reticulum (ER) localized PIN5 and PIN8 maintain the intracellular auxin homeostasis. Although an antagonistic activity of PIN5 and PIN8 proteins in regulating the intracellular auxin homeostasis and other developmental events have been reported, the membrane topology of these proteins, which might be a basis for their antagonistic function, is poorly understood. In this study we optimized digitonin based PM-permeabilizing protocols coupled with immunocytochemistry labeling to map the membrane topology of PIN5 and PIN8 in Arabidopsis thaliana root cells. Our results indicate that, except for the similarities in the orientation of the N-terminus, PIN5 and PIN8 have an opposite orientation of the central hydrophilic loop and the C-terminus, as well as an unequal number of transmembrane domains (TMDs). PIN8 has ten TMDs with groups of five alpha-helices separated by the central hydrophilic loop (HL) residing in the ER lumen, and its N- and C-terminals are positioned in the cytoplasm. However, the topology of PIN5 comprises nine TMDs. Its N-terminal end and the central HL face the cytoplasm while its C-terminus resides in the ER lumen. Overall, this study shows that PIN5 and PIN8 proteins have a divergent membrane topology while introducing a toolkit of methods for studying membrane topology of integral proteins including those localized at the ER membrane.

Migration behavior of iron and phosphorus during gas-based reduction for high-phosphorus iron ore

With the depletion of high-grade iron ore, it is necessary to develop low-quality high-phosphorus iron ore through economical and sustainable solutions. In this study, we presented simultaneous enrichment of iron (Fe) and phosphorus (P) to recover P from high-phosphorus iron ore and clarified the migration of P from the original apatite to reduced iron during the direct reduction process. To capture the migration route, gas-based reduction at a relatively slow rate was conducted on two typical iron ores samples (low-grade and high-grade) at different temperatures and times. Results indicate that there are concentration gradients for P and Fe of reaction products in the low-grade iron ore at 1400 °C. The P content continuously increased in the sequence from metallic iron (Fe), wustite (FeO), and fayalite (Fe2SiO4), to apatite (Ca3(PO4)3F). Conversely, the content of Fe gradually decreased. During this process, P dissolved from apatite entered and formed P-bearing fayalite. For the high-grade iron ore, P-bearing fayalite with a metastable structure disappeared as the reduction progressed, and P was released and then reduced to a gaseous state, finally absorbed by metallic iron. Furthermore, when metallic iron was not formed in the initial 60 min at 1300 °C, the P migrated from the apatite to the fayalite and gas phase. As the reduction time increased from 60 min to 240 min, the formed metallic iron provided a site for gasified P, which inhibited the volatilization of P and contributed to Fe and P enrichment.