Spectroscopic characterization of the warfarin drug-binding site of folded and unfolded human serum albumin anchored on gold nanoparticles: effect of bioconjugation on the loading capacity

Protein-conjugated gold nanoparticles (AuNPs) have recently shown promising applications in medicine, owing to their inertness and biocompatibility. Herein, we studied the spectroscopy of 25 nm diameter AuNPs, coated with human serum albumin (HSA) as a model drug carrier. The morphology and coating of the AuNPs were examined using transmission electron microscopy and dynamic light scattering. Resonance energy transfer from the sole tryptophan of HSA (Trp214) to the AuNPs indicates a single layer of protein coverage. Using fluorescein (FL) to probe the warfarin drug-binding site in HSA revealed an increase in the HSA–FL binding by ∼4.5 times when HSA is anchored on the nanoparticle surface, indicating a rise in the loading capacity. Femtosecond transient absorption measurements of the surface plasmonic resonance band of the AuNPs show three ultrafast dynamics that are involved in the relaxation process. The three decay components were assigned to the electron–electron (∼400 fs), electron–phonon (∼2.0 ps) and phonon–phonon (200–250 ps) interactions. These dynamics were not changed upon coating the AuNPs with HSA which indicates the chemical and physical stability of the AuNPs upon bioconjugation. Chemical unfolding of the warfarin binding site with guanidine hydrochloride (GdnHCl) was studied by measuring the spectral shift in the Trp214 fluorescence and the appearance of the Tyr fluorescence. Unfolding was shown to start at [GdnHCl] ≥ 2.0 M and is complete at [GdnHCl] = 6.0 M. HSA anchored onto the nanoparticle surface shows more resistance to the unfolding effect which is attributed to the stability of the native form of HSA on the nanoparticle surface. On the other hand, upon complete unfolding, a larger red shift in the Trp214 fluorescence was observed for the HSA–AuNP complex. This observation indicates that, upon unfolding, the HSA molecule is still anchored on the AuNP surface in which subdomain IIA is facing the outer water molecules in the bulk solution as well as the hydration shell rather than the core of the nanoparticle. The current study is important for a better understanding of the physical and dynamical properties of protein-coated metal nanoparticles, which is expected to help in optimizing their properties for critical applications in nanomedicine.

This work investigates the steady-state and ultrafast spectroscopy of bioconjugated gold nanoparticles and the implications on the protein binding activity and drug-loading capacity.     

Capacitive performance of vertically aligned reduced titania nanotubes coated with Mn2O3 by reverse pulse electrodeposition

In this study, a composite material, manganese oxide/reduced titania nanotubes (Mn₂O₃/R-TNTs), was synthesized through incorporation of Mn₂O₃ onto R-TNTs via the reverse pulse electrodeposition technique. The influence of pulse reverse duty cycles on the morphological, structural and electrochemical performance of the surface was studied by varying the applied duty cycle from 10% to 90% for 5 min total on-time at an alternate potential of −0.90 V (E_on) and 0.00 V (E_off). FESEM analysis revealed the uniform deposition of Mn₂O₃ on the circumference of the nanotubes. The amount of Mn₂O₃ loaded onto the R-TNTs increased as a higher duty cycle was applied. Cyclic voltammetry and galvanostatic charge–discharge tests were employed to elucidate the electrochemical properties of all the synthesized samples in 1 M KCl. The specific capacitance per unit area was greatly enhanced upon the incorporation of Mn₂O₃ onto R-TNTs, but showed a decrease as a high duty cycle was applied. This proved that low amounts of Mn₂O₃ loading enhanced the facilitation of the active ions for charge storage purposes. The optimized sample, Mn₂O₃/R-TNTs synthesized at 10% duty cycle, exhibited high specific capacitance of 18.32 mF cm⁻² at a current density of 0.1 mA cm⁻² obtained from constant current charge–discharge measurements. This revealed that the specific capacitance possessed by Mn₂O₃/R-TNTs synthesized at 10% duty cycle was 6 times higher than bare R-TNTs.

Mn₂O₃ was coated onto reduced titania nanotubes by reverse pulse electrodeposition, showing smooth and homogenous deposits without covering the opening of the nanotubes.     

A review of Hib epidemiology in Asia.

Meningitis due to an invasive Haemophilus influenzae type b (Hib) infection, has been previously perceived to be relatively uncommon in Asia. However, the incidence of disease and its impact may have been underestimated. In addition to a lack of microbiological facilities in some hospitals, difficulties in culturing the organism and the widespread use of antibiotics may have hidden the true incidence of the disease in some countries. Furthermore, the reported disease burden probably underestimates the incidence of Hib pneumonia. The epidemiology of invasive Hib disease for various Asian nations is reviewed in this paper. Hospital-based studies show that Hib is a major cause of bacterial meningitis and/or pneumonia in the Philippines, India, Thailand, Malaysia, Indonesia and Vietnam. Singapore and Hong Kong have a low incidence of infection compared with Western and other Asian nations. This low incidence is not due to a higher level of natural protective antibodies, but may be related to an interaction between environmental and genetic factors. Therefore the widespread belief that Hib infection is unimportant in Asia does not refer to Asia as a whole and possibly to Chinese patients only, and failure to recognize this has serious implications. The inclusion of Hib vaccine in the routine infant immunization schedule in many industrialized nations has significantly reduced the incidence of invasive disease. Recent studies have shown Hib vaccination is also effective in preventing invasive disease in children in developing countries. While population-based data may be required to confirm the need for public-funded infant Hib immunization in Asia, its introduction in countries with a high incidence of Hib meningitis and/or pneumonia has the potential to significantly improve pediatric health and survival.     

基于转录组测序筛选和田羊毛囊周期性变化过程中差异表达miRNAs以及初步分析

为了探讨miRNAs在和田羊毛囊周期性变化中皮肤组织的表达差异,同时预测其在和田羊毛囊周期性变化过程中发挥的潜在功能.本研究选取和田羊毛囊周期性变化的生长期(P1、5月份、n=3)、退行期(P2、10月份、n=3)以及休止期(P3、次年1月份、n=3)的皮肤毛囊组织为材料进行转录组测序和分析.结果共鉴定了143个已知miRNAs并预测了759个新miRNAs,显示相较于P1组,P2组共鉴定了173个显著差异表达miRNAs,其中包含7个显著上调的miRNAs与166个显著下调的miRNAs;而在P3组中鉴定了243个差异表达miRNAs,其中包含28个显著上调的miRNAs与215个显著下调的miRNAs;相较于P2组,P3组共鉴定了71个显著差异表达miRNAs,其中包含23个显著上调的miRNAs与48个显著下调的miRNAs.针对差异表达miRNAs进行靶基因预测和功能分析,发现靶基因显著富集在与毛囊发育相关的激素水平调节、细胞分解代谢、周期蛋白结合、骨细胞发育等GO条目中以及与毛囊发育相关的AMPK、Hedgehog、TNF等信号通路中.在和田羊毛囊周期性变化过程中差异表达miRNAs可能通过以上通路调控靶基因的表达进而参与和田羊毛囊的周期性变化过程.     

Frequent detection and characterization of hepatitis E virus variants in wild rats (Rattus rattus) in Indonesia

One hundred sixteen rats (Rattus rattus) captured in Indonesia from 2011 to 2012 were investigated for the prevalence of hepatitis E virus (HEV)-specific antibodies and HEV RNA. Using an ELISA based on HEV genotype 4 with an ad hoc cutoff value of 0.500, 18.1 % of the rats tested positive for anti-HEV IgG. By nested RT-PCR, 14.7 % of the rats had rat HEV RNA, and none were positive for HEV genotype 1-4. A high HEV prevalence among rats was associated with lower sanitary conditions in areas with a high population density. Sixteen of the 17 HEV isolates obtained from infected rats showed >93.0 % nucleotide sequence identity within the 840-nucleotide ORF1-ORF2 sequence and were most closely related to a Vietnamese strain (85.9-87.9 % identity), while the remaining isolate differed from known rat HEV strains by 18.8-23.3 % and may belong to a novel lineage of rat HEV. These results suggest a wide distribution of rat HEV with divergent genomes.