An investigation of quantum dot theranostic probes for prostate and leukemia cancer cells using a CdZnSeS QD-based nanoformulation.

Anticancer theranostic nanocarriers have the potential to enhance the efficacy of pharmaceutical evaluation of drugs. Semiconductor nanocrystals, also known as quantum dots (QDs), are particularly promising components of drug carrier systems due to their small sizes and robust photoluminescence properties. Herein, bright CdZnSeS quantum dots were synthesized in a single step via the hot injection method. The particles have a quasi-core/shell structure as evident from the high quantum yield (85 %), which decreased to 41 % after water solubilization. These water solubilized QDs were encapsulated into gallic acid / alginate (GA-Alg) matrices to fabricate imaging QDs@mod-PAA/GA-Alg particles with enhanced stability in aqueous media. Cell viability assessments demonstrated that these nanocarriers exhibited viability ranging from 63 % to 83 % across all tested cell lines. Furthermore, the QDs@mod-PAA/GA-Alg particles were loaded with betulinic acid (BA) and ceranib-2 (C2) for in vitro drug release studies against HL-60 leukemia and PC-3 prostate cancer cells. The BA loaded QDs@mod-PAA/GA-Alg had a half-maximal inhibitory concentration (IC50) of 8.76 µg/mL against HL-60 leukemia cells, which is 3-fold lower than that of free BA (IC50 = 26.55 µg/mL). Similar enhancements were observed with nanocarriers loaded with C2 and simultaneously with both BA and C2. Additionally, BA:C2 loaded QDs@mod-PAA/GA-Alg nanocarriers displayed a similar enhancement (IC50 = 3.37 µg/mL compared against IC50 = 11.68 µg/mL for free BA:C2). The C2 loaded QDs@mod-PAA/GA-Alg nanocarriers had an IC50 = 2.24 µg/mL against HL-60 cells. C2 and BA loaded QDs@mod-PAA/GA-Alg NCr had IC50 values of 7.37 µg/mL and 24.55 µg/mL against PC-3 cells, respectively.

Dielectronic satellite emission from a solid-density Mg plasma: Relationship to models of ionization potential depression.

We report on experiments where solid-density Mg plasmas are created by heating with the focused output of the Linac Coherent Light Source x-ray free-electron laser. We study the K-shell emission from the helium- and lithium-like ions using Bragg crystal spectroscopy. Observation of the dielectronic satellites in lithium-like ions confirms that the M-shell electrons appear bound for these high charge states. An analysis of the intensity of these satellites indicates that when modeled with an atomic-kinetics code, the ionization potential depression model employed needs to produce depressions for these ions which lie between those predicted by the well known Stewart-Pyatt and Ecker-Kroll models. These results are largely consistent with recent density functional theory calculations.

Synthesis of High Sn Content Ge1-x-ySixSny (0.1 < y < 0.22) Semiconductors on Si for MWIR Direct Band Gap Applications.

A systematic effort has been described to grow ternary Ge1-x-ySixSny semiconductors on silicon with high Sn concentrations spanning the 9.5-21.2% range. The ultimate goal is not only to produce direct band gap materials well into the infrared region of the spectrum but also to approach a critical concentration (yc) for which further additions of Si would decrease─rather than increase─the band gap. This counterintuitive behavior is expected as a result of the giant bowing parameter in the compositional dependence of the band gap associated with the presence of Si-Sn pairs. The growth approach in this study was based on a chemical vacuum deposition method that uses Si4H10, Ge3H8, and SnD4 or SnH4 as the sources of Si, Ge, and Sn, respectively. A fixed Si concentration near x = 0.05-0.07 was chosen to focus the exploration of the compositional space. A first family of samples was grown of Ge-buffered Si substrates. For Sn concentrations y < 0.12, it was found that the samples relaxed their mismatch strain in situ during growth, resulting in high Sn content films that had relatively low levels of strain and exhibited photoluminescence signals that demonstrated direct band gap behavior for the first time. The device potential of these materials was also demonstrated by fabricating a prototype photodiode with low dark currents. The optical studies suggest that the above-mentioned critical concentration is close to yc = 0.2. As the growth temperature was lowered in an effort to reach such values, Sn concentrations as high as y = 0.15 were obtained, but the films grew fully strained with compressive levels as high as 1.7%. To increase the Sn concentration beyond y = 0.15, a new strategy was adopted, in which the Ge buffer layer was eliminated, and the ternary alloy was grown directly on Si. The much higher lattice mismatch between the Ge1-x-ySixSny layer and the Si substrate caused strain relaxation right at the film/substrate interface, and the subsequent films grew with much lower levels of strain. This made it possible to lower the growth temperatures even further and achieve a comprehensive series of strained relaxed samples with tunable Sn concentrations as high as y = 0.21 (and beyond). The latter represent the highest Sn contents in crystalline Ge1-x-ySixSny attained to date and reach the desired yc = 0.2 range. The synthesized films exhibited significant thickness, allowing a thorough determination of composition, crystallinity, morphology, and bonding properties, indicating the formation of single-phase single-crystal alloys with random cubic structures. Further work will focus on optimizing the latter samples to explore the optical and electronic properties.

Heart transplantation and human immunodeficiency virus-navigating drug-drug interactions: a case report.

BACKGROUND: Antiretroviral therapy (ART) has led to a decline in human immunodeficiency virus (HIV)-related mortality, but comorbidities, including organ dysfunction, are increasingly the focus of care. Heart transplant (HT) is a very effective therapeutic strategy for end-stage heart failure (HF); however, clinicians may be hesitant due to concerns of complex drug-drug interactions (DDIs) between ART and HT immunosuppressive regimens and the potential impact of ART on long-term HT outcomes. In this report, we describe long-term (76-month) follow-up of a patient with HIV-positive status who underwent orthotopic HT with special emphasis on complex drug interactions. CASE PRESENTATION: A 58-year-old man with HIV-1 developed ischemic cardiomyopathy, progressed to end-stage HF and underwent orthotopic HT. To avoid DDIs with planned immunosuppressive therapies, the ART regimen was modified to consist of lamivudine, tenofovir disoproxil fumarate, rilpivirine, and raltegravir. Following HT, the patient's immunosuppression consisted of tacrolimus and mycophenolate mofetil. He has had normal cardiac function and no opportunistic infections and was subsequently switched to tenofovir alafenamide, emtricitabine, and bictegravir in combination for convenience. Serial HIV-1 RNA blood levels were constantly below the limit of quantification, and his CD4 count remained above 200 cells/mm3 (30-35%). Several DDIs were identified and addressed; however, his long-term post-HT complications included one episode of asymptomatic acute cellular rejection, adenocarcinoma of the prostate, basal cell carcinoma, cardiac allograft vasculopathy, and peripheral neuropathy. CONCLUSION: The clinical outcome of this case supports the conclusion of previously published reports, summarized here within, demonstrating that HIV-1 positive status should not preclude HT in carefully selected individuals. Both addressing potential DDIs prior to HT and long-term monitoring for routine post-transplant complications and secondary and incidental malignancies are imperative.

Experimental measurements and numerical simulations of the transport and retention of nanocrystal CdSe/ZnS quantum dots in saturated porous media: Effects of electrolytes, organic ligand, and natural organic matter.

This study explores the transport and retention of CdSe/ZnS quantum dot (QD) nanoparticles in water-saturated sand columns as a function of electrolytes (Na+ and Ca2+), ionic strength, organic ligand citrate, and Suwannee River natural organic matter (SRNOM). Numerical simulations were carried out to understand the mechanisms that govern the transport and interactions of QDs in porous media and to assess how environmental parameters impact these mechanisms. An increase in the ionic strength of NaCl and CaCl2 increased QDs retention in porous media. The reduction of the electrostatic interactions screened by dissolved electrolyte ions and the increase of divalent bridging effect are the causes for this enhanced retention behavior. Citrate or SRNOM enhanced QDs transport in NaCl and CaCl2 systems by either increasing the repulsion energy barrier or inducing the steric interactions between QDs and the quartz sand collectors. A non-exponential decay characterized the retention profiles of QDs along the distance to the inlet. The modeling results indicated the four models containing the attachment, detachment, and straining terms - Model 1: M1-attachment, Model 2: M2-attachment and detachment, Model 3: M3-straining, and Model 4: M4-attachment, detachment, and straining - closely simulated the observed breakthrough curves (BTCs) but inadequately described the retention profiles.

Exponentiated model of drug demand is preferred over exponential models in people with daily/near daily cannabis use.

Cannabis use is a growing health concern emphasizing the need to better understand the complexities of drug choice in people with daily/near daily cannabis use. Hypothetical purchasing tasks provide a means to collect data on drug consumption behavior without requiring drug administration and have been used to isolate behavioral economic factors of choice, including facets of drug demand in substance using populations. Various models are used for analyzing hypothetical purchasing task data, but challenges exist in modeling data sets with consumption values of zero. Additionally, a single model or approach may not be best for all commodities and drug classes. This study compared two common demand models (exponential vs. exponentiated) applied to identical hypothetical purchasing task data from 21 (n = 21) individuals with daily/near daily cannabis use. The exponential model was fit using three common levels of replacement values for zero consumption (.1, .01, .001) and compared to the exponentiated model without replacement values. We found that the exponentiated model produced significantly better model fits for individual data, compared to all exponential models. Additionally, significant differences for model derived values of demand elasticity and intensity were found between the exponentiated model and different levels of the exponential model. We conclude that the exponentiated model is preferred over the exponential model for performing demand analysis on hypothetical purchasing task data from individuals with daily/near daily cannabis use. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

A diminutive snake species can maintain regional heterothermy in both homogeneous and heterogeneous thermal environments.

Regional heterothermy is a pattern whereby different body regions are maintained at different temperatures, often to prioritize the function of certain body parts over others, or to maximize the function of organs and tissues that vary in thermal sensitivity. Regional heterothermy is relatively well understood in endotherms, where physiological mechanisms maintain heterogeneity. However, less is known about regional heterothermy in ectotherms, where behavioral mechanisms are more important for generating thermal variation. In particular, whether small and elongate ectotherms with high surface area to volume ratios such as diminutive snakes can maintain regional heterothermy, despite rapid thermal equilibration, is not yet known. We measured regional variation in body temperature and tested whether environmental heterogeneity is used to generate regional heterothermy in the ring-necked snake (Diadophis punctatus) using both field and laboratory studies. We found that ring-necked snakes have robust regional heterothermy in a variety of contexts, despite their small body size and elongate body shape. Temperature variation along the length of their bodies was not detectable when measured externally. However, snakes had higher mouth than cloacal temperatures both in the field and in laboratory thermal gradients. Further, this regional heterothermy was maintained even in ambient laboratory conditions, where the thermal environment was relatively homogeneous. Our results indicate that regional heterothermy in ring-necked snakes is not solely driven by environmental variation but is instead linked to physiological or morphological mechanisms that maintain regional variation in body temperature irrespective of environmental context.

Imaging x-ray spectrometer at the high energy density instrument of the European x-ray free electron laser.

A multipurpose imaging x-ray crystal spectrometer is developed for the high energy density instrument of the European X-ray Free Electron Laser. The spectrometer is designed to measure x rays in the energy range of 4-10 keV, providing high-resolution, spatially resolved spectral measurements. A toroidally bent germanium (Ge) crystal is used, allowing x-ray diffraction from the crystal to image along a one-dimensional spatial profile while spectrally resolving along the other. A detailed geometrical analysis is performed to determine the curvature of the crystal. The theoretical performance of the spectrometer in various configurations is calculated by ray-tracing simulations. The key properties of the spectrometer, including the spectral and spatial resolution, are demonstrated experimentally on different platforms. Experimental results prove that this Ge spectrometer is a powerful tool for spatially resolved measurements of x-ray emission, scattering, or absorption spectra in high energy density physics.

Fluorescence Intermittency of Quantum Dot-Organic Dye Conjugates: Implications for Alternative Energy and Biological Imaging.

Quantum dot (QD)-organic dye couple chromophores are topical due to their applications in biology, catalysis, and energy. The maximization of energy transfer efficiency can be guided by the underlying Förster or Dexter mechanisms; however, the impact of fluorescence intermittency must also be considered. Here we demonstrate that the average ⟨ton⟩ and ⟨toff⟩ times of dye acceptors in coupled QD-dye chromophores are substantially affected by the donors' blinking behavior. With regard to biological imaging, this effect beneficially minimizes the photobleaching of the acceptor dye. The implications for alternative energy are less encouraging as the acceptors' capacity to store energy, using ⟨ton⟩/⟨toff⟩ as a metric, was reduced by as much as ∼95%. These detrimental effects can be mitigated by suppressing QD blinking via surface treatment. This study also demonstrates several instances of the nonconformity of QD blinking dynamics to a power law distribution, as a robust examination of the off times reveals log-normal behavior that is consistent with the Albery model.

Impact of Inpatient Initiation of SGLT2 Inhibitors on Diuretic Requirements in Patients With Heart Failure.

Background: Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have been shown to improve outcomes in patients with heart failure (HF) and are now included in guideline-directed medical therapy. Trials reporting the change in loop diuretic dose following SGLT2i initiation have indicated conflicting results. There is no clear guidance on whether reducing loop diuretic doses following SGLT2i initiation is appropriate. Objective: The purpose of this study is to assess the impact of SGLT2i initiation on diuretic adjustment in hospitalized patients with known or new HF. Methods: This was a retrospective, single health-system study assessing the change in loop diuretic dose in the 60 days following discharge for patients with HF initiated on SGLT2i therapy during a hospital admission or upon discharge. Secondary outcomes assessed effect on renal function and discontinuation of SGLT2i within the 60 day follow up period. Results: Forty percent of patients required loop diuretic dose adjustment, with 29% requiring a dose reduction within the 60 days following discharge. There was minimal change in serum creatinine or blood urea nitrogen. The SGLT2i was discontinued in 6 patients. Conclusions: After inpatient initiation of SGLT2is, approximately one-third of patients required a reduction in loop diuretic dose within 60 days following hospital discharge. Further study is recommended to confirm if empiric diuretic dose adjustments are appropriate in this HF population.

Parabolic Potential Surfaces Localize Charge Carriers in Nonblinking Long-Lifetime "Giant" Colloidal Quantum Dots.

Materials for studying biological interactions and for alternative energy applications are continuously under development. Semiconductor quantum dots are a major part of this landscape due to their tunable optoelectronic properties. Size-dependent quantum confinement effects have been utilized to create materials with tunable bandgaps and Auger recombination rates. Other mechanisms of electronic structural control are under investigation as not all of a material's characteristics are affected by quantum confinement. Demonstrated here is a new structure-property concept that imparts the ability to spatially localize electrons or holes within a core/shell heterostructure by tuning the charge carrier's kinetic energy on a parabolic potential energy surface. This charge carrier separation results in extended radiative lifetimes and in continuous emission at the single-nanoparticle level. These properties enable new applications for optics, facilitate novel approaches such as time-gated single-particle imaging, and create inroads for the development of other new advanced materials.

Evaluating the evidence for sacubitril/valsartan across the continuum of heart failure.

Since initial publication of the PARADIGM-HF trial in 2014, sacubitril/valsartan has been investigated in various settings to establish optimal use, further expanding its indications in patients with heart failure (HF). Although numerous studies have been published, until recently these have primarily involved post hoc analyses from the PARADIGM-HF study itself with a consistent focus on use of sacubitril/valsartan in patients with HF with reduced ejection fraction (HFrEF). This has led to a gap in the literature regarding utility of sacubitril/valsartan in other HF subpopulations. The aim of this review is to provide a summary of recent clinical trials further expanding use and guideline recommendations for sacubitril/valsartan. The findings of 15 studies, including clinical trials and post hoc analyses, are summarized and describe the use of sacubitril/valsartan in additional HF subpopulations, such as HFrEF following hospitalization for acute decompensated HF and advanced HF, HF with preserved ejection fraction (HFpEF), and HF postmyocardial infarction. In addition, three studies investigating timing of initiation, dose titration regimens, and cost-effectiveness are examined. Select ongoing trials are also reviewed to demonstrate the continued commitment to further advance care of patients with HF. This comprehensive review serves as a resource for health care providers who pursue optimal utilization of sacubitril/valsartan in their respective clinical practices.

Fluorescent Artificial Antigens Revealed Extended Membrane Networks Utilized by Live Dendritic Cells for Antigen Uptake.

Dendritic cells (DCs) can infiltrate tight junctions of the epithelium to collect remote antigens during immune surveillance. While elongated membrane structures represent a plausible structure to perform this task, their functional mechanisms remain elusive owing to the lack of high-resolution characterizations in live DCs. Here, we developed fluorescent artificial antigens (FAAs) based on quantum dots coated with polyacrylic acid. Single-particle tracking of FAAs enables us to superresolve the membrane fiber network responsible for the antigen uptake. Using the DC2.4 cell line as a model system, we discovered the extensive membrane network approaching 200 µm in length with tunnel-like cavities about 150 nm in width. The membrane fiber network also contained heterogeneous circular migrasomes. Disconnecting the membrane network from the cell body decreased the intracellular FAA density. Our study enables mechanistic investigations of DC membrane networks and nanocarriers that target this mechanism.

Selective augmentation of corticospinal motor drive with trans-spinal direct current stimulation in the cat.

BACKGROUND: A key outcome for spinal cord stimulation for neurorehabilitation after injury is to strengthen corticospinal system control of the arm and hand. Non-invasive, compared with invasive, spinal stimulation minimizes risk but depends on muscle-specific actions for restorative functions. OBJECTIVE: We developed a large-animal (cat) model, combining computational and experimental techniques, to characterize neuromodulation with transcutaneous spinal direct current stimulation (tsDCS) for facilitation of corticospinal motor drive to specific forelimb muscles. METHODS: Acute modulation of corticospinal function by tsDCS was measured using motor cortex-evoked muscle potentials (MEPs). The effects of current intensity, polarity (cathodal, anodal), and electrode position on specific forelimb muscle (biceps vs extensor carpi radialis, ECR) MEP modulation were examined. Locations of a key target, the motoneuron pools, were determined using neuronal tracing. A high-resolution anatomical (MRI and CT) model was developed for computational simulation of spinal current flow during tsDCS. RESULTS: Effects of tsDCS on corticospinal excitability were robust and immediate, therefore supporting MEPs as a sensitive marker of tsDCS targeting. Varying cathodal/anodal current intensity modulated MEP enhancement/suppression, with higher cathodal sensitivity. Muscle-specificity depended on cathode position; the rostral position preferentially augmented biceps responses and the caudal position, ECR responses. Precise anatomical current-flow modeling, supplemented with target motor pool distributions, can explain tsDCS focality on muscle groups. CONCLUSION: Anatomical current-flow modeling with physiological validation based on MEPs provides a framework to optimize muscle-specific tsDCS interventions. tsDCS targeting of representative motor pools enables muscle- and response-specific neuromodulation of corticospinal motor drive.

Leveraging lifetime information to perform real-time 3D single-particle tracking in noisy environments.

A microscopy platform that leverages the arrival time of individual photons to enable 3D single-particle tracking of fast-moving (translational diffusion coefficient of ≃3.3 µm2/s) particles in high-background environments is reported here. It combines a hardware-based time-gating module, which enables the rate of photon processing to be as high as 100 MHz, with a two-photon-excited 3D single-particle tracking confocal microscope to enable high sample penetration depth. Proof-of-principle experiments where single quantum dots are tracked in solutions containing dye-stained cellulose, are shown with tracking performance markedly improved using the hardware-based time-gating module. Such a microscope design is anticipated to be of use to a variety of communities who wish to track single particles in cellular environments, which commonly have high fluorescence and scattering background.

Cytosolic delivery of membrane-penetrating QDs into T cell lymphocytes: implications in immunotherapy and drug delivery.

We report single-particle characterization of membrane-penetrating semiconductor quantum dots (QDs) in T cell lymphocytes. We functionalized water-soluble CdSe/CdZnS QDs with a cell-penetrating peptide composed of an Asp-Ser-Ser (DSS) repeat sequence. DSS and peptide-free control QDs displayed concentration-dependent internalization. Intensity profiles from single-particle imaging revealed a propensity of DSS-QDs to maintain a monomeric state in the T cell cytosol, whereas control QDs formed pronounced clusters. Single-particle tracking showed a direct correlation between individual QD clusters' mobility and aggregation state. A significant portion of control QDs colocalized with an endosome marker inside the T cells, while the percentage of DSS-QDs colocalized dropped to 9%. Endocytosis inhibition abrogated the internalization of control QDs, while DSS-QD internalization only mildly decreased, suggesting an alternative cell-entry mechanism. Using 3D single-particle tracking, we captured the rapid membrane-penetrating activity of a DSS-QD. The ability to characterize membrane penetrating activities in live T cells creates inroads for the optimization of gene therapy and drug delivery through the use of novel nanomaterials.

High-resolution inelastic x-ray scattering at the high energy density scientific instrument at the European X-Ray Free-Electron Laser.

We introduce a setup to measure high-resolution inelastic x-ray scattering at the High Energy Density scientific instrument at the European X-Ray Free-Electron Laser (XFEL). The setup uses the Si (533) reflection in a channel-cut monochromator and three spherical diced analyzer crystals in near-backscattering geometry to reach a high spectral resolution. An energy resolution of 44 meV is demonstrated for the experimental setup, close to the theoretically achievable minimum resolution. The analyzer crystals and detector are mounted on a curved-rail system, allowing quick and reliable changes in scattering angle without breaking vacuum. The entire setup is designed for operation at 10 Hz, the same repetition rate as the high-power lasers available at the instrument and the fundamental repetition rate of the European XFEL. Among other measurements, it is envisioned that this setup will allow studies of the dynamics of highly transient laser generated states of matter.

A Real-Time Blood Flow Measurement Device for Patients with Peripheral Artery Disease.

PURPOSE: To evaluate the feasibility of a new optical device that measures peripheral blood flow as a diagnostic and monitoring tool for patients with peripheral artery disease (PAD). MATERIALS AND METHODS: In this prospective study, 167 limbs of 90 patients (mean age, 76 y; 53% men) with suspected PAD were evaluated with the FlowMet device, which uses a new type of dynamic light-scattering technology to assess blood flow in real time. Measurements of magnitude and phasicity of blood flow were combined into a single-value flow-waveform score and compared vs ankle-brachial index (ABI), toe-brachial index (TBI), and clinical presentation of patients per Rutherford category (RC). Receiver operating characteristic curves were constructed to predict RC. Area under the curve (AUC), sensitivity, and specificity were compared among flow-waveform score, ABI, and TBI. RESULTS: Qualitatively, the FlowMet waveforms were analogous to Doppler velocity measurements, and degradation of waveform phasicity and amplitude were observed with increasing PAD severity. Quantitatively, the flow, waveform, and composite flow-waveform scores decreased significantly with decreasing TBI. In predicting RC ≥ 4, the flow-waveform score (AUC = 0.83) showed a linear decrease with worsening patient symptoms and power comparable to that of TBI (AUC = 0.82) and better than that of ABI (AUC = 0.71). Optimal sensitivity and specificity pairs were found to be 56%/83%, 72%/81%, and 89%/74% for ABI, TBI, and flow-waveform score, respectively. CONCLUSIONS: The technology tested in this pilot study showed a high predictive value for diagnosis of critical limb ischemia. The device showed promise as a diagnostic tool capable of providing clinical feedback in real time.

Experimental measurements and numerical simulations of the transport and retention of nanocrystal CdSe/ZnS quantum dots in saturated porous media: effects of pH, organic ligand, and natural organic matter.

The risks of environmental exposures of quantum dot (QD) nanoparticles are increasing, but these risks are difficult to assess because fundamental questions remain about factors affecting the mobility of QDs. The objective of this study is to help address this shortcoming by evaluating the physico-chemical mechanisms controlling the transport and retention of CdSe/ZnS QDs under various environmental conditions. The approach was to run a series of laboratory-scale column experiments where QDs were transported through saturated porous media with different pH values and concentrations of citrate and Suwannee River natural organic matter (SRNOM). Numerical simulations were then conducted and compared with the laboratory data in order to evaluate parameters controlling transport. QD suspensions were injected into the column in an upward direction and ICP-MS used to analyze Cd2+ concentrations (C) in column effluent and sand porous media samples. The increase in the background solution pH values enhanced the QD transport and decreased the QD retention. QD transport recovery percentages obtained from the column effluent samples were 2.6%, 83.2%, 101.7%, 96.5%, and 98.9%, at pH levels of 1.5, 3.5, 5, 7, and 9, respectively. The effects of citrate and SRNOM on the transport and retention of QDs were pH dependent as reflected in the influence of the electrostatic and steric interactions between QDs and sand surfaces. QDs were mobile under unfavorable deposition conditions at environmentally relevant pHs (i.e., 5, 7, and 9). Under favorable pH conditions for deposition (i.e., 1.5), QDs were completely retained within the porous media. The retention profiles of QDs showed a non-exponential decay with distance to the inlet, attributed to multiple deposition rates caused by the QD particles and surface heterogeneities of the quartz silica sand. Results of the diameter ratios of QDs to the median sand grains, in suspensions of DI water at pH 1.5, of citrate at pH 1.5, and of citrate at pH 3.5 indicate straining as the dominating mechanism for QD retention in porous media. The blocking effect and straining were significant under favorable deposition conditions and the detachment effect was non-negligible under unfavorable deposition conditions. Physico-chemical attachment and straining are the governing mechanisms that control the retention of QDs. Overall, experimental results indicate that aggregation, deposition, straining, blocking, and DLVO-type interactions affect the advective transport and retention of QDs in saturated porous media. The simulations were conducted using models that include terms describing attachment, detachment, and straining terms-model 1: M1-attachment, model 2: M2-attachment and detachment, model 3: M3-straining, and model 4: M4-attachment, detachment, and straining. The results from simulations with M2-attachment and detachment and M4-attachment, detachment, and straining matched best the observed breakthrough curves, but all four models inadequately described the retention profiles. Our findings demonstrate that QDs are mobile in porous media under a wide range of physico-chemical conditions representative of the natural environment. The mobility behavior of QDs in porous media indicated the potential risk of soil and groundwater contamination.