Brain Pathology in COVID-19: Clinical Manifestations and Potential Mechanisms.

Neurological manifestations of coronavirus disease 2019 (COVID-19) are less noticeable than the respiratory symptoms, but they may be associated with disability and mortality in COVID-19. Even though Omicron caused less severe disease than Delta, the incidence of neurological manifestations is similar. More than 30% of patients experienced "brain fog", delirium, stroke, and cognitive impairment, and over half of these patients presented abnormal neuroimaging outcomes. In this review, we summarize current advances in the clinical findings of neurological manifestations in COVID-19 patients and compare them with those in patients with influenza infection. We also illustrate the structure and cellular invasion mechanisms of SARS-CoV-2 and describe the pathway for central SARS-CoV-2 invasion. In addition, we discuss direct damage and other pathological conditions caused by SARS-CoV-2, such as an aberrant interferon response, cytokine storm, lymphopenia, and hypercoagulation, to provide treatment ideas. This review may offer new insights into preventing or treating brain damage in COVID-19.

Sub-Anesthesia Dose of S-Ketamine Reduces Postoperative Pain and Anxiety in Patients Receiving Breast and Thyroid Surgery: A Randomized, Controlled Trial.

BACKGROUND: Postoperative pain and anxiety affect patients' recovery and increase the family burden. S-ketamine presents analgesic effects and anti-depressive effects in clinics. The effect of a sub-anesthesia dose of S-ketamine on postoperative pain and anxiety remains to be clarified. OBJECTIVES: This study aimed to evaluate the analgesic and anxiolytic effects of a sub-anesthesia dose of S-ketamine on postoperative pain and anxiety and explored the risk factors for postoperative pain in patients receiving breast or thyroid surgery under general anesthesia. STUDY DESIGN: A randomized, double-blind, controlled trial. SETTING: A university hospital. METHODS: One hundred twenty patients receiving breast or thyroid surgery, stratified by surgery type, were randomized to S-ketamine and control groups in a 1:1 ratio. S-ketamine (0.3 mg/kg) or an equal volume of normal saline was administrated after anesthesia induction. Visual analog scale (VAS) of pain and self-rating anxiety scale (SAS) were tested before surgery and on postoperative day 1, 2, and 3. VAS and SAS score between the 2 groups were compared, and the risk factors for postoperative moderate to severe pain were explored with logistic regression analysis. RESULTS: Intraoperative S-ketamine decreased VAS and SAS scores on postoperative day 1, 2, and 3 (P < 0.05, 2-way ANOVA for repeated measurements followed by Bonferroni post-analysis). Subgroup analysis showed S-ketamine decreased VAS and SAS scores both in breast surgery and thyroid surgery patients on postoperative day 1, 2, and 3. Logistic regression identified S-ketamine and regular exercise are protective factors, and anxiety before surgery is a risk factor for postoperative moderate to severe pain (P < 0.05). LIMITATIONS: The anxiety score in our study is not so high, which may under-evaluate the anxiolytic effect of S-ketamine. However, S-ketamine decreased the SAS scores postoperatively in our study. CONCLUSIONS: Intraoperative sub-anesthesia dose of S-ketamine reduces postoperative pain and anxiety intensity. Anxiety before surgery is a risk factor, and S-ketamine and regular exercise are protective factors for postoperative pain. The study was registered at www.chictr.org.cn with the number: ChiCTR2200060928.

Ghost images with controllable visibility and spatial resolution.

We designed a kind of speckle field with controllable visibility and speckle grain size through a modified Gerchberg-Saxton algorithm based on Fresnel diffraction. Ghost images with independently controllable visibility and spatial resolution were demonstrated based on the designed speckle fields, which could be of much higher visibility and spatial resolution than those with pseudothermal light. In addition, speckle fields capable of reconstructing ghost images simultaneously on multiple different planes were customized. These results could be of potential applications on optical encryption and optical tomography.

Association of sleep duration with chronic constipation among adult men and women: Findings from the National Health and Nutrition Examination Survey (2005-2010).

Background: Previous studies suggested that unhealthy sleep patterns were closely associated with gastrointestinal diseases, but the impact of unhealthy sleep duration on chronic constipation has not been well studied until now. In this study, we aim to explore the association between sleep duration and constipation among males and females. Methods: We utilized the US National Health and Nutrition Examination Surveys data from 2005 to 2010, and adults (≥20 years old) who completed the sleep and bowel health questionnaires were enrolled in this observational study. Sleep duration was categorized into four groups: very short sleep (<5 h/night), short sleep (5-6 h/night), normal sleep (7-8 h/night), and long sleep (≥9 h/night). Chronic constipation was defined as Bristol Stool Scale Type 1(separate hard lumps, like nuts) or Type 2(sausage-like but lumpy). Controlling demographic, lifestyle, and dietary factors, the logistic regression model in Generalized Linear Model (GLM) function was used to estimate the correlation of sleep duration with constipation among men and women. Results: Of the 11,785 individuals (51.2% males and 48.8% females), 4.3% of men and 10.2% of women had constipation, respectively. More than half of patients with constipation did not adopt the recommended sleep duration. Compared with normal individuals, male participants with constipation had a higher proportion of shorter sleep duration (41.0 vs. 32.3% in the short sleep group and 6.3 vs. 4.7% in the very short sleep group), and female individuals with constipation had a higher proportion of long sleep duration (12.7 vs. 8.2%). After covariates adjustment, men with short sleep duration (5-6 h/night) correlated with increased odds for constipation (OR:1.54, 95%CI:1.05-2.25), and women with long sleep duration (≥9 h/night) linked to the higher constipation risk (OR:1.58, 95%CI:1.10-2.29). Excessive sleep duration in males or insufficient sleep duration in females was neither linked to increased nor decreased constipation risk. Conclusions: In this observational study of a nationally representative sample of adults, we demonstrate a differential impact of unhealthy sleep duration on constipation among men and women. Short sleep duration poses a higher risk of constipation in men, and excessive sleep duration correlates with higher constipation risk in women.

Tools Are Needed to Promote Sedation Practices for Mechanically Ventilated Patients.

Suboptimal sedation practices continue to be frequent, although the updated guidelines for management of pain, agitation, and delirium in mechanically ventilated (MV) patients have been published for several years. Causes of low adherence to the recommended minimal sedation protocol are multifactorial. However, the barriers to translation of these protocols into standard care for MV patients have yet to be analyzed. In our view, it is necessary to develop fresh insights into the interaction between the patients' responses to nociceptive stimuli and individualized regulation of patients' tolerance when using analgesics and sedatives. By better understanding this interaction, development of novel tools to assess patient pain tolerance and to define and predict oversedation or delirium may promote better sedation practices in the future.

Treating highly complex anal fistula with a new method of combined intraoperative endoanal ultrasonography (IOEAUS) and transanal opening of intersphincteric space (TROPIS).

INTRODUCTION: Treatment of highly complex anal fistula is still a profound test for a specialist colorectal surgeon. The reasons are directly related to recurrence and incontinence. AIM: To evaluate the clinical results of a combined method of intraoperative endoanal ultrasonography (IOEAUS) and transanal opening of the intersphincteric space (TROPIS). MATERIAL AND METHODS: This study retrospectively included 48 patients with complex anal fistula, all of whom underwent new surgical methods. This operation mainly consists of two steps. Firstly, the type of anal fistula was determined by endoanal ultrasonography (EAUS) or magnetic resonance imaging (MRI) before the operation. Then the TROPIS procedure was performed with the help of EAUS, and the decision on whether a drainage seton should be placed depended on the condition of the tract. If there were secondary tracts, they were found and the same was done. RESULTS: The median follow-up was 12 months. Two (4.1%) patients experienced recurrence. Four (8.3%) patients did not have primary healing. All 6 patients underwent the same procedure again, and three recovered completely. So total successful fistula healing was observed in 45 (93.7%). There were no major complications and no significant deterioration in anal function and incontinence postoperatively. CONCLUSIONS: Combined IOEAUS and TROPIS is an effective procedure in the treatment of highly complex anal fistula, and it may offer a new means for other operations.

Glucose and pH Dual-Responsive Polymersomes with Multilevel Self-Regulation of Blood Glucose for Insulin Delivery.

Smart insulin delivery systems now play essential roles in diabetes treatment, whereas most existing systems suffer from insufficient regulation against blood glucose. Here, a glucose and pH dual-responsive insulin delivery system with multilevel self-regulation of blood glucose was constructed. Photocross-linked dual-responsive polymersomes were prepared by the self-assembly of the diblock copolymer methoxyl poly(ethylene glycol)-b-poly[3-acrylamidophenylboronic acid-co-2-(diethylamino)ethyl methacrylate-co-2-hydroxy-4-(methacryloyloxy)benzophenone] (mPEG-b-P(AAPBA-co-DEAEMA-co-BMA)) synthesized by reversible addition-fragmentation chain transfer polymerization (RAFT), where insulin and glucose oxidase (GOx) were co-encapsulated inside. It is worth noting that the polymersomes with tunable membrane permeability are the first glucose-responsive platform consisting of both PBA and GOx. According to the pH change produced by gluconic acid, the pH-sensitive monomer DEAEMA endowed the polymersome membrane with multilevelly tunable and self-regulative permeability, further controlling the release behavior of insulin. This multilevel tunability was reflected directly in in vitro insulin release tests and was proven by the self-regulation of blood glucose in vivo. Promisingly, the polymersomes have great potential to be applied for the self-regulation of blood glucose in the treatment of diabetes.

Dual-responsive polymersomes as anticancer drug carriers for the co-delivery of doxorubicin and paclitaxel.

Multi stimuli-responsive polymersomes are in high demand as smart drug carriers, particularly for the treatment of complex cancers. However, most polymersomes have multi-responsiveness that does not affect each other and focus on single drug loading. Here, we have designed photo-crosslinked temperature and pH dual-responsive polymersomes by the self-assembly of a triblock polymer of methoxyl poly(ethylene glycol)-b-poly(N-isopropylacrylamide)-b-poly[2-(diethylamino)ethyl methacrylate-co-2-hydroxy-4-(methacryloyloxy)benzophenone] (mPEG-b-PNIPAM-b-P(DEAEMA-co-BMA)) synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT). The dual-responsive polymersomes had a layered membrane, resulting in tunable permeability. Importantly, the polymersomes were proved to have a pH-controlled temperature-responsiveness. A hydrophilic-hydrophobic drug pair (doxorubicin hydrochloride, DOX, and paclitaxel, PTX) could be co-encapsulated in the fabricated polymersomes. The membrane permeability based on its layered structure was triggered by the change in temperature and pH to permit the separate control on the release of DOX and PTX. In a simulated tumor microenvironment, DOX and PTX encapsulated in the polymersomes could take effect for a relatively longer period and could work synergistically. Thus, the photo-crosslinked and dual-responsive polymersomes can be considered as promising drug carriers in the field of tumor combination chemotherapy.

Photocatalytic degradation of dye by Ag/TiO2 nanoparticles prepared with different sol-gel crystallization in the presence of effluent organic matter.

TiO2 nanoparticle-doped Ag (Ag/TNPs) have good photocatalytic properties based on localized surface plasmon resonance (LSPR) effect. The effluent organic matter (EfOM) can be easily activated by photo-excitation to promote pollutant photodegradation, but excessive EfOM has an inactive effect. Herein, the purpose of this paper is to investigate the changes of photocatalytic performance by Ag/TNPs in the presence of EfOM. Three Ag/TNPs made by condensation crystallization or rotary evaporation crystallization using the sol-gel method were conducted in photocatalytic degradation of methyl orange (MO). The Ag/TNPs crystallized by condensation had greater separation rate of photogenerated electron-hole pairs and photocatalytic degradation of MO with high load rates of binding Ag and TiO2 than those formed by rotary evaporation crystallization. Indeed, EfOM could be excited to produce the active substances under illumination resulting in the promotion of MO degradation. However, contrary to previous speculation, no additive effect of MO photodegradation was observed with the addition both of EfOM and Ag/TNPs at different pH values (5~9) and ion strength (0~0.4 mol L-1). It can be explained that the EfOM changed the morphology and active sites in Ag/TNPs' surface. Meanwhile, EfOM could be consumed and degraded by Ag/TNP photocatalysis leading to the concentration of free radicals to decrease. This study revealed a nonsynergistic effect between nanomaterial and EfOM for photocatalysis. EfOM would have a negative effect on photocatalytic degradation of organic compounds by Ag/TNPs in the aquatic environment. Graphical abstract .

Correlation and expression analysis of hypoxia-inducible factor 1α, glucose transporter 1 and lactate dehydrogenase 5 in human gastric cancer.

The development and identification of novel potential targeting sites for intervention therapy are essential in the search for improved treatment methods for gastric cancer (GC). Previously, it has been reported that hypoxia inducible factor-1α (HIF-1α) is a potential target gene involved in the endogenous hypoxic response and bioenergetic metabolism of GC cells. In the present study, with the assumption of a close interplay among HIF-1α, glucose transporter 1 (GLUT1) and lactate dehydrogenase-5 (LDH-5), 85 patients with GC were recruited and the protein and gene expression levels of HIF-1α, GLUT1 and LDH-5 in tumor tissues were evaluated in order to assess clinical correlations and co-expression patterns, using Immunohistochemical staining and reverse transcription-quantitative polymerase chain reaction. The results demonstrated that the protein and gene expression levels of HIF-1α were significantly associated with the depth of invasion, nodal metastasis, clinical stage, differentiation and distant metastasis. Consistent with the protein expression results, the mRNA expression levels of the genes coding for GLUT1 and LDH-5 were clearly associated with tumor size, depth of invasion, distant metastasis, clinical stage and differentiation. Correlation analysis of HIF-1α with GLUT1 and LDH-5 at the protein and mRNA expression levels in gastric carcinoma indicated that HIF-1α expression was positively correlated with the expression of GLUT1 (P<0.01, r=0.765 for mRNA expression; P<0.01, r=0.697 for protein expression) and LDH-5 (P<0.01, r=0.892 for mRNA expression; P<0.01, r=0.783 for protein expression) at the mRNA and protein levels. Therefore, it may be concluded that HIF-1α, GLUT1 and LDH-5 are potential target genes involved in the endogenous tumor response to hypoxia and the inhibition of tumor energy metabolism, highlighting a novel therapeutic target for GC.

The Influence of Age on Sensitivity to Dexmedetomidine Sedation During Spinal Anesthesia in Lower Limb Orthopedic Surgery.

To investigate the influence of age on sensitivity to dexmedetomidine sedation in adult patients, we selected 79 patients scheduled for lower limb orthopedic surgery under spinal anesthesia to identify the dexmedetomidine ED50 for adequate sedation among different age groups. After a spinal anesthetic was placed, a dose of dexmedetomidine determined by the Dixon up-and-down method was administered over 15 minutes. The ED50 in the elderly group was lower than in the other 2 groups (elderly: 0.88 ± 0.07; middle aged: 1.16 ± 0.08; young: 1.21 ± 0.06 µg/kg; both P < .001). There was no difference between the young and middle-aged groups (P = .160).

Pharmacokinetic and pharmacodynamics of intravenous dexmedetomidine in morbidly obese patients undergoing laparoscopic surgery.

BACKGROUND: This study was designed to investigate the pharmacokinetics and pharmacodynamics of dexmedetomidine in morbidly obese patients undergoing laparoscopic surgery. METHODS: Morbidly obese (body mass index ≥40 kg/m2) and normal weight patients scheduled for elective laparoscopic surgery were included (n = 8, each group). After baseline hemodynamic measurement, dexmedetomidine 1 µg/kg was administered over 10 min. General anesthesia was induced with propofol 1.5 mg/kg and fentanyl 4 µg/kg 20 min after completion of dexmedetomidine infusion; the lungs were mechanically ventilated after tracheal intubation. The pharmacokinetics of dexmedetomidine was analyzed by a noncompartment model. Hemodynamic data and peripheral oxygen saturation (SpO2) were measured up to 30 min after starting dexmedetomidine infusion. Sedation level was measured with the Observer's Assessment of Alertness/Sedation (OAA/S) scale. RESULTS: Peak plasma concentration, area under the curve to infinity, elimination half-life, and apparent volume of distribution were significantly larger in morbidly obese than in normal weight patients (3.75 ± 0.56 vs. 2.54 ± 0.32 µg/l, P < 0.001; 2174 ± 335 vs. 1594 ± 251 ng h/l, P < 0.001; 225 ± 55 vs. 158 ± 53 min, P = 0.02; 310 ± 63 vs. 164 ± 41 l, P < 0.001, respectively). Although clearance was also higher in obese patients than in normal body weight patients (58.6 ± 10.7 vs. 44.9 ± 9.0 l/h, P = 0.02), it was lower in obese patients than in normal body weight patients after normalization to total body weight (0.47 ± 0.07 vs. 0.64 ± 0.09 l/h/kg, P < 0.001). There were no differences in systolic or diastolic blood pressure or heart rate between the two groups within the 30 min. Sedation level was deeper and SpO2 was lower in morbidly obese than in normal weight patients. More patients in the morbidly obese patient group experienced deeper sedation after the start of the dexmedetomidine infusion (P < 0.05). CONCLUSION: The pharmacokinetics and pharmacodynamics of dexmedetomidine are significantly different in morbidly obese patients compared with normal weight patients. Level of sedation was significantly deeper, and oxygen saturation was significantly lower, in morbidly obese than in normal weight patients, probably resulting from higher plasma concentration after infusion of 1.0 µg/kg. CLINICAL TRIAL NUMBER, REGISTRY URL: ClinicalTrials.gov (NCT01864187), https://register.clinicaltrials.gov/prs/app/action/LoginUser?ts=1&cx=-jg9qo4 .

Hexanediamine functionalized poly (glycidyl methacrylate-co-N-vinylpyrrolidone) particles for bilirubin removal.

In this study, we provided a facile method to prepare adsorbents with high content of amino groups for bilirubin removal. Poly (glycidyl methacrylate-co-N-vinylpyrrolidone) particle adsorbents were prepared through free radical solution copolymerization followed by a phase inversion technique. Amino groups were further introduced onto the particles by grafting 1,6-hexanediamine molecules. The porosity and specific surface area of the functional particles were 92.9% and 11.8m2/g, respectively. Flourier transform infrared spectroscopy and elemental analysis confirmed the successful functionalization of polymeric particles. The cross-linker content and N-vinylpyrrolidone ratios had significant influence on the pore structure of the polymeric particles, as observed by scanning electron microscopy. Batch adsorption experiments were performed to verify bilirubin adsorption behavior of the particles, and a particle column was fabricated to further study the bilirubin removal. The particles exhibited good adsorption capacity of bilirubin without procoagulant activity, and had great potential to be used in hemoperfusion. The study opens a new route to fabricate functional polymer adsorbents.

Continuous wound infusion of ropivacaine for the control of pain after thoracolumbar spinal surgery: a randomized clinical trial.

PURPOSE: A prospective randomized clinical trial was carried out to observe the analgesic efficacy of ropivacaine for postoperative pain following thoracolumbar spinal surgery. METHODS: Seventy-one patients with elective posterior thoracolumbar spinal surgery were randomly divided into two groups. Local group received 0.33 % ropivacaine by pump through the wound, and intravenous group received flurbiprofen axetil, pentazocine and palonosetron via intravenous pump. We evaluated the level of pain, the incidence of adverse reactions at 2, 4, 6, 12, 24, 36 and 48 h after operation, and the occurrence of chronic pain 3 months later. RESULTS: There were no significant differences in the pain level between the two groups. However, the incidence of nausea, vomiting and chronic pain was significantly lower in the local group. CONCLUSIONS: Our results showed that local infusion of ropivacaine achieved similar analgesic effects to intravenous delivery of analgesic drugs, but significantly reduced incidence of nausea, vomiting and chronic pain.

Heparin-Like Chitosan Hydrogels with Tunable Swelling Behavior, Prolonged Clotting Times, and Prevented Contact Activation and Complement Activation.

The aim of this study was to create heparin-like chitosan hydrogels (HLCHs) for blood purification. Herein, we prepared two heparin-like chitosans (HLCSs) with various carboxymethyl and sulfate groups, followed by a cross-linking reaction with glutaraldehyde. The synthetic chitosan derivatives were characterized by X-ray photoelectron spectroscopy, gel permeation chromatography, FTIR and NMR. The average sulfonation degrees of two HLCSs were 0.69 and 0.94 per sugar unit, respectively. The swelling ratio of the HLCH could reach up to 4800%, and the HLCHs remained a well-defined shape and stable below 170 °C. Moreover, the activated partial thromboplastin time and thrombin time results indicated that both of the HLCSs and their hydrogels exhibited excellent thrombus inhibition property. Furthermore, the contact activation and complement activation results also proved that the hydrogels possessed good blood compatibility and had the potential to be used as blood-contacting materials.

Influence of material properties on TiO2 nanoparticle agglomeration.

Emerging nanomaterials are being manufactured with varying particle sizes, morphologies, and crystal structures in the pursuit of achieving outstanding functional properties. These variations in these key material properties of nanoparticles may affect their environmental fate and transport. To date, few studies have investigated this important aspect of nanoparticles' environmental behavior. In this study, the aggregation kinetics of ten different TiO2 nanoparticles (5 anatase and 5 rutile each with varying size) was systematically evaluated. Our results show that, as particle size increases, the surface charge of both anatase and rutile TiO2 nanoparticles shifts toward a more negative value, and, accordingly, the point of zero charge shifts toward a lower value. The colloidal stability of anatase sphere samples agreed well with DLVO theoretical predictions, where an increase in particle size led to a higher energy barrier and therefore greater critical coagulation concentration. In contrast, the critical coagulation concentration of rutile rod samples correlated positively with the specific surface area, i.e., samples with higher specific surface area exhibited higher stability. Finally, due to the large innate negative surface charge of all the TiO2 samples at the pH value (pH = 8) tested, the addition of natural organic matter was observed to have minimal effect on TiO2 aggregation kinetics, except for the smallest rutile rods that showed decreased stability in the presence of natural organic matter.

Accumulation and toxicity of metal oxide nanoparticles in a soft-sediment estuarine amphipod.

Estuarine and marine sediments are a probable end point for many engineered nanoparticles (ENPs) due to enhanced aggregation and sedimentation in marine waters, as well as uptake and deposition by suspension-feeding organisms on the seafloor. Benthic infaunal organisms living in sediments encounter relatively high concentrations of pollutants and may also suffer toxic effects of ENPs. We tested whether three heavily used metal oxide ENPs, zinc oxide (ZnO), copper oxide (CuO), and nickel oxide (NiO) were toxic to an estuarine amphipod, Leptocheirus plumulosus. We used results from 10-day laboratory bioassays to estimate potential demographic impacts of ENP exposure. We also evaluated fate and transport pathways of the ENPs in the experiments to elucidate routes of uptake and exposure. Dissolved Zn was found in sediment pore water and overlying water samples at 10 fold the concentrations of Cu or Ni, a pattern indicative of the relatively high dissolution rate of ZnO ENPs compared with CuO and NiO ENPs. Accumulation of metals in amphipod tissues increased with exposure concentrations for all three ENPs, suggesting possible exposure pathways to higher taxa. Amphipods accumulated ≤600 µg Zn and Cu g(-1) and 1000 µg Ni g(-1). Amphipod mortality increased with ZnO and CuO concentrations, but showed no significant increase with NiO to concentrations as high as 2000 µg g(-1). The median lethal concentration in sediment (LC50) of ZnO was 763 µg g(-1) and 868 µg g(-1) for CuO ENPs. Our results indicate that ZnO and CuO ENPs, but not NiO ENPs, are toxic to L. plumulosus and that ZnO toxicity primarily results from Zn ion exposure while CuO toxicity is due to nanoparticle exposure.

Dispersion stability and electrokinetic properties of intrinsic plutonium colloids: implications for subsurface transport.

Subsurface transport of plutonium (Pu) may be facilitated by the formation of intrinsic Pu colloids. While this colloid-facilitated transport is largely governed by the electrokinetic properties and dispersion stability (resistance to aggregation) of the colloids, reported experimental data is scarce. Here, we quantify the dependence of ζ-potential of intrinsic Pu(IV) colloids on pH and their aggregation rate on ionic strength. Results indicate an isoelectric point of pH 8.6 and a critical coagulation concentration of 0.1 M of 1:1 electrolyte at pH 11.4. The ζ-potential/pH dependence of the Pu(IV) colloids is similar to that of goethite and hematite colloids. Colloid interaction energy calculations using these values reveal an effective Hamaker constant of the intrinsic Pu(IV) colloids in water of 1.85 × 10(-19) J, corresponding to a relative permittivity of 6.21 and refractive index of 2.33, in agreement with first principles calculations. This relatively high Hamaker constant combined with the positive charge of Pu(IV) colloids under typical groundwater aquifer conditions led to two contradicting hypotheses: (a) the Pu(IV) colloids will exhibit significant aggregation and deposition, leading to a negligible subsurface transport or (b) the Pu(IV) colloids will associate with the relatively stable native groundwater colloids, leading to a considerable subsurface transport. Packed column transport experiments supported the second hypothesis.

Photoinduced disaggregation of TiO2 nanoparticles enables transdermal penetration.

Under many aqueous conditions, metal oxide nanoparticles attract other nanoparticles and grow into fractal aggregates as the result of a balance between electrostatic and Van Der Waals interactions. Although particle coagulation has been studied for over a century, the effect of light on the state of aggregation is not well understood. Since nanoparticle mobility and toxicity have been shown to be a function of aggregate size, and generally increase as size decreases, photo-induced disaggregation may have significant effects. We show that ambient light and other light sources can partially disaggregate nanoparticles from the aggregates and increase the dermal transport of nanoparticles, such that small nanoparticle clusters can readily diffuse into and through the dermal profile, likely via the interstitial spaces. The discovery of photoinduced disaggregation presents a new phenomenon that has not been previously reported or considered in coagulation theory or transdermal toxicological paradigms. Our results show that after just a few minutes of light, the hydrodynamic diameter of TiO(2) aggregates is reduced from ∼280 nm to ∼230 nm. We exposed pigskin to the nanoparticle suspension and found 200 mg kg(-1) of TiO(2) for skin that was exposed to nanoparticles in the presence of natural sunlight and only 75 mg kg(-1) for skin exposed to dark conditions, indicating the influence of light on NP penetration. These results suggest that photoinduced disaggregation may have important health implications.