Use of TOF-SIMS to study adsorption and loading behavior of methylene blue and papain in a nano-porous silicon layer

Agricultural waste materials for adsorptive removal of phenols, chromium (VI) and cadmium (II) from wastewater: A review

Management of basic natural resources and the spent industrial and domestic streams to provide a sustainable safe environment for healthy living is a magnum challenge to scientists and environmentalists. The present remedial approach to the wastewater focuses on recovering pure water for reuse and converting the contaminants into a solid matrix for permanent land disposal. However, the ground water aquifers, over a long period slowly leach the contaminants consequently polluting the ground water. Synthetic adsorbents, mainly consisting of polymeric resins, chelating agents, etc. are efficient and have high specificity, but ultimate disposal is a challenge as most of these materials are non-biodegradable. In this context, it is felt appropriate to review the utility of adsorbents based on natural green materials such as agricultural waste and restricted to few model contaminants: phenols, and heavy metals chromium(VI), and cadmium(II) in view of the vast amount of literature available. The article discusses the features of the agricultural waste material-based adsorbents including the mechanism. It is inferred that agricultural waste materials are some of the common renewable sources available across the globe and can be used as sustainable adsorbents. A discussion on challenges for industrial scale implementation and integration with advanced technologies like magnetic-based approaches and nanotechnology to improve the removal efficiency is included for future prospects.

Mesoporous Silica Particles as Drug Delivery Systems-The State of the Art in Loading Methods and the Recent Progress in Analytical Techniques for Monitoring These Processes

Conventional administration of drugs is limited by poor water solubility, low permeability, and mediocre targeting. Safe and effective delivery of drugs and therapeutic agents remains a challenge, especially for complex therapies, such as cancer treatment, pain management, heart failure medication, among several others. Thus, delivery systems designed to improve the pharmacokinetics of loaded molecules, and allowing controlled release and target specific delivery, have received considerable attention in recent years. The last two decades have seen a growing interest among scientists and the pharmaceutical industry in mesoporous silica nanoparticles (MSNs) as drug delivery systems (DDS). This interest is due to the unique physicochemical properties, including high loading capacity, excellent biocompatibility, and easy functionalization. In this review, we discuss the current state of the art related to the preparation of drug-loaded MSNs and their analysis, focusing on the newest advancements, and highlighting the advantages and disadvantages of different methods. Finally, we provide a concise outlook for the remaining challenges in the field.

Visible Light Assisted Organosilane Assembly on Mesoporous Silicon Films and Particles

Porous silicon (PSi) is a versatile matrix with tailorable surface reactivity, which allows the processing of a range of multifunctional films and particles. The biomedical applications of PSi often require a surface capping with organic functionalities. This work shows that visible light can be used to catalyze the assembly of organosilanes on the PSi, as demonstrated with two organosilanes: aminopropyl-triethoxy-silane and perfluorodecyl-triethoxy-silane. We studied the process related to PSi films (PSiFs), which were characterized by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (ToF-SIMS) and field emission scanning electron microscopy (FESEM) before and after a plasma patterning process. The analyses confirmed the surface oxidation and the anchorage of the organosilane backbone. We further highlighted the surface analytical potential of ¹³C, ¹⁹F and ²⁹Si solid-state NMR (SS-NMR) as compared to Fourier transformed infrared spectroscopy (FTIR) in the characterization of functionalized PSi particles (PSiPs). The reduced invasiveness of the organosilanization regarding the PSiPs morphology was confirmed using transmission electron microscopy (TEM) and FESEM. Relevantly, the results obtained on PSiPs complemented those obtained on PSiFs. SS-NMR suggests a number of siloxane bonds between the organosilane and the PSiPs, which does not reach levels of maximum heterogeneous condensation, while ToF-SIMS suggested a certain degree of organosilane polymerization. Additionally, differences among the carbons in the organic (non-hydrolyzable) functionalizing groups are identified, especially in the case of the perfluorodecyl group. The spectroscopic characterization was used to propose a mechanism for the visible light activation of the organosilane assembly, which is based on the initial photoactivated oxidation of the PSi matrix.

QCM-D and ToF-SIMS Investigation to Deconvolute the Relationship between Lipid Adsorption and Orientation on Lipase Activity

Quartz crystal microbalance with dissipation (QCM-D) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to provide insights into the relationship between lipid adsorption kinetics and molecular behavior in porous silica particles of varying hydrophobicities on lipase activity. Lipase (an interfacial enzyme that cleaves ester bonds to break down lipids to fatty acids and monoglycerides) activity was controlled by loading triglycerides at different surface coverages in hydrophilic and hydrophobic porous silica particles. The rate of lipid adsorption increased 2-fold for the hydrophobic surface compared to the hydrophilic surface. However, for submonolayer lipid coverage, the hydrophilic surface enhanced lipase activity 4-fold, whereas the hydrophobic surface inhibited lipase activity 16-fold, compared to lipid droplets in water. A difference in lipid orientation for low surface coverage, evidenced by ToF-SIMS, indicated that lipid adsorbs to hydrophilic silica in a conformation promoting hydrolysis. Multilayer coverage on hydrophobic and hydrophilic surfaces was indistinguishable with ToF-SIMS analysis. Increased lipid adsorption for both substrates facilitated digestion kinetics comparable to a conventional emulsion. Improved understanding of the interfacial adsorption and orientation of lipid and its digestibility in porous silica has implications in improving the uptake of pharmaceuticals and nutrients from lipid-based delivery systems.

Polyethyleneimine for copper absorption II: kinetics, selectivity and efficiency from seawater

Nano-thin coatings of glutaraldehyde cross-linked polyethyleneimine effectively and selectively accumulated copper from natural seawater.

Low temperature thermal dependent Filgrastim adsorption behavior detected with ToF-SIMS

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) detected changes in Filgrastim (granulocyte colony stimulating growth factor, G-CSF) adsorption behavior at a solid interface when exposed to temperatures as low as 35 °C, i.e., before thermal denaturation, was detected by circular dichroism (CD) or dynamic light scattering (DLS). Biopharmaceuticals rely on maintaining sufficient conformation to impart correct biological function in vivo. Stability of such molecules is critical during synthesis, storage, transport, and administration. CD analysis indicated loss of structure at temperatures greater than ~60 °C, while DLS detected aggregation at ~42 °C. Furthermore, we demonstrate the nature of G-CSF interaction with a surface was altered rapidly and at relatively low temperatures. Specifically, after 10 min thermal treatment, changes in adsorption behavior occurred at 35 °C indicated by principal component analysis of spectra as primarily due to increasing yields of methionine fragments. This was likely to be due to either altering the preferential protein orientation upon adsorption or greater denaturation exposing the hydrophobic core. This investigation demonstrates the sensitivity of ToF-SIMS in studying biopharmaceutical adsorption and conformational change and can assist with studies into promoting their stability.

Reference values of elements in human hair: a systematic review

BACKGROUND

The lack of systematic review on reference values of elements in human hair with the consideration of methodological approach. The absence of worldwide accepted and implemented universal reference ranges causes that hair mineral analysis has not become yet a reliable and useful method of assessment of nutritional status and exposure of individuals.

OBJECTIVES

Systematic review of reference values of elements in human hair.

DATA SOURCES

PubMed, ISI Web of Knowledge, Scopus.

STUDY ELIGIBILITY CRITERIA

Humans, hair mineral analysis, elements or minerals, reference values, original studies.

RESULTS

The number of studies screened and assessed for eligibility was 52. Eventually, included in the review were 5 papers. The studies report reference ranges for the content of elements in hair: macroelements, microelements, toxic elements and other elements. Reference ranges were elaborated for different populations in the years 2000-2012. The analytical methodology differed, in particular sample preparation, digestion and analysis (ICP-AES, ICP-MS). Consequently, the levels of hair minerals reported as reference values varied.

CONCLUSIONS

It is necessary to elaborate the standard procedures and furtherly validate hair mineral analysis and deliver detailed methodology. Only then it would be possible to provide meaningful reference ranges and take advantage of the potential that lies in Hair Mineral Analysis as a medical diagnostic technique.

Surface chemistry of porous silicon and implications for drug encapsulation and delivery applications

Porous silicon (pSi) has a number of unique properties that appoint it as a potential drug delivery vehicle; high loading capacity, controllable surface chemistry and structure, and controlled release properties. The native Si(y)SiH(x) terminated pSi surface is highly reactive and prone to spontaneous oxidation. Surface modification is used to stabilize the pSi surface but also to produce surfaces with desired drug delivery behavior, typically via oxidation, hydrosilylation or thermal carbonization. A number of advanced characterization techniques have been used to analyze pSi surface chemistry, including X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry. Surface modification not only stabilizes the pSi surface but determines its charge, wettability and dissolution properties. Manipulation of these parameters can impact drug encapsulation by altering drug-pSi interactions. pSi has shown to be a successful vehicle for the delivery of poorly soluble drugs and protein therapeutics. Surface modification influences drug pore penetration, crystallinity, loading level and dissolution rate. Surface modification of pSi shows great potential for drug delivery applications by controlling pSi-drug interactions. Controlling these interactions allows specific drug release behaviors to be engineered to aid in the delivery of previously challenging therapeutics. Within this review, different pSi modification techniques will be outlined followed by a summary of how pSi surface modification has been used to improve drug encapsulation and delivery.

Hair analysis as a biomonitor for toxicology, disease and health status

Hair analysis receives a large amount of academic and commercial interest for wide-ranging applications. However, in many instances, especially for elemental or 'mineral' analysis, the degree of success of analytical interpretation has been quite minimal with respect to the extent of such endeavors. In this critical review we address the questions surrounding hair analysis with specific intent of discovering what hair concentrations can actually relate to in a biogenic sense. This is done from a chemistry perspective to explain why and how elements are incorporated into hair and their meaning. This includes an overview of variables attributed to altering hair concentrations, such as age, gender, melanin content, and other less reported factors. Hair elemental concentrations are reviewed with regard to morbidity, with specific examples of disease related effects summarized. The application of hair analysis for epidemiology and etiology studies is enforced. A section is dedicated specifically to the area of population studies with regards to mercury, which highlights how endogenous and exogenous incorporation relies on species dependant metabolism and metabolic products. Many of the considerations are relevant to other areas of interest in hair analysis, such as for drug and isotopic analysis. Inclusion of a table of elemental concentrations in hair should act as a valuable reference (298 references).

Detecting the presence of denatured human serum albumin in an adsorbed protein monolayer using TOF-SIMS

We demonstrate the application of time-of-flight secondary ion mass spectrometry (TOF-SIMS) in conjunction with multivariate statistics to differentiate trace levels of denatured proteins in adsorbed monolayers; specifically, human serum albumin (HSA) on oxidized silicon substrates. Subtle differences in protein conformation due to thermal denaturation of HSA, unable to be determined by dynamic light scattering nor circular dichroism, were differentiated by TOF-SIMS. The fragmentation pattern is highly sensitive to protein conformation, allowing assessment of relative amounts of proteins in mixtures and quantifying amounts of denatured protein in a sample. Discussion is presented on ascribing orientation and conformational differences between samples based upon TOF-SIMS spectra. This has implications for detecting denatured protein in biotechnology and medical applications.