Somnath Singh

Effect of polyols on the conformational stability and biological activity of a model protein lysozyme.

The purpose of this study was to investigate the stabilizing action of polyols against various protein degradation mechanisms (eg, aggregation, deamidation, oxidation), using a model protein lysozyme. Differential scanning calorimeter (DSC) was used to measure the thermodynamic parameters, mid point transition temperature and calorimetric enthalpy, in order to evaluate conformational stability. Enzyme activity assay was used to corroborate the DSC results. Mannitol, sucrose, lactose, glycerol, and propylene glycol were used as polyols to stabilize lysozyme against aggregation, deamidation, and oxidation. Mannitol was found to stabilize lysozyme against aggregation, sucrose against deamidation both at neutral pH and at acidic pH, and lactose against oxidation. Stabilizers that provided greater conformational stability of lysozyme against various degradation mechanisms also protected specific enzyme activity to a greater extent. It was concluded that DSC and bioassay could be valuable tools for screening stabilizers in protein formulations.

Smart Polymers for Controlled Delivery of Proteins and Peptides: A Review of Patents

Protein and peptide-based therapeutic agents have unique physiochemical properties such as high molecular weight, short half life, requirement of a sustained plasma level for the desired therapeutic effect, liable to physical and chemical instability by gastric enzymes and harsh acidic environment as well as first pass metabolism, which makes their delivery a challenge. The delivery of proteins and peptides using various routes of administration like oral, nasal, rectal, pulmonary, buccal, vaginal and transdermal route is found to exhibit limitations, poor permeability and degradation being major limitations. Use of parenteral route is found to overcome these problems but patient compliance is poor due to the need for frequent administration. Use of control delivery for these drugs using smart polymers seems promising as they overcome the limitations posed by other routes of delivery. Smart polymers increase patient compliance, maintain stability of the drug, and maintain drug level in therapeutic window and are easy to manufacture. Different types of smart polymer-based delivery systems, such as sensitive to temperature, phase, pH, electric charge, light, and biochemicals, and their application in controlling the release of the incorporated drug to obtain a sustained plasma level has been discussed. Smart polymers, however, face challenges with regard to high burst release, unpredictable behavior in later part of biphasic release profile, overall drug release kinetics, conformational stability during processing, and preserving biological activity after getting released. Several patents overcoming these inherent problems associated with smart polymers have been reviewed. At the end, the future direction and potential of smart polymer-based delivery system for drug delivery has been presented in brief.

IN VITRO PERMEABILITY AND BINDING OF HYDROCARBONS IN PIG EAR AND HUMAN ABDOMINAL SKIN

Human skin has continual exposure to chemicals due to various occupational activities. Chemicals that get on skin have the potential to be absorbed. Hence, the potential human health hazards of a chemical must include an estimate for percutaneous absorption. An inexpensive, easy, and adequate model for the quantitative measurement of skin penetration of chemicals from JP-8 is absent. Cutaneous penetration studies in vitro through human skin are severely limited due to the lack of availability of the human skin. In this study, we have shown that pig ear skin can be used as a model for risk assessment from the percutaneous absorption of chemicals. We determined flux and permeability coefficient (Kp) of three chemicals – heptane, hexadecane, and xylene – from their permeation profile through porcine and human skin. Binding of these chemicals to porcine stratum corneum (SC) and human SC were also determined. Factors of difference (FOD) in the permeability of pig and human skin were 1.71, 1.28, and 1.16, respectively, for heptane, hexadecane, and xylene. FOD in binding of heptane, hexdecane, and xylene to pig and human SC were found to be 1.04, 0.76, and 1.31, respectively. Since, FOD for permeability and binding parameters were less than 2, hence, we conclude that pig ear skin can be used as model for humans for risk assessment from percutaneous absorption of chemicals.

Effect of menthone on the in vitro percutaneous absorption of tamoxifen and skin reversibility

The effect of penetration enhancer (i.e., 1, 2, 3 and 5% menthone in combination with 50% ethanol (EtOH)) was investigated on the in vitro percutaneous absorption of tamoxifen, and post-recovery epidermal permeability after removal of the above enhancer. The flux of tamoxifen with menthone in combination with 50% EtOH was significantly greater (P<0.05) than the control (50% EtOH). The flux of tamoxifen increased with increasing concentrations of menthone. The post-recovery flux through enhancer exposed epidermis was significantly decreased (P<0.05) as compared to pre-recovery. However, post-recovery flux of tamoxifen through the enhancer-exposed epidermis did not completely recover to the baseline (i.e., post-recovery flux through phosphate buffered saline, pH 7.4 treated epidermis).

In vivo percutaneous absorption, skin barrier perturbation, and irritation from JP-8 jet fuel components

Abstract JP-8 jet fuel has been reported to cause systemic and dermal toxicities in animal models and humans. There is a great potential for human exposure to JP-8. In this study, we determined percutaneous absorption and dermal toxicity of three components of JP-8 (i.e., xylene, heptane, and hexadecane) in vivo in weanling pigs. In vivo percutaneous absorption results suggest a greater absorption of hexadecane (0.43%) than xylene (0.17%) or heptane (0.14%) of the applied dose after 30 min exposure. Transepidermal water loss (TEWL) provides a robust method for assessing damage to the stratum corneum. Heptane showed greater increase in TEWL than the other two chemicals. No significant (p<0.05) increase in temperature was observed at the chemically treated site than the control site. Heptane showed greater TEWL values and erythema score than other two chemicals (xylene and hexadecane). We did not observe any skin reactions or edema from these chemicals. Erythema was completely resolved after 24 h of the patch removal in case of xylene and hexadecane.

Dermal toxicity: effect of jet propellant-8 fuel exposure on the biophysical, macroscopic and microscopic properties of porcine skin

The effect of jet propellant-8 (JP-8) fuel exposure on the biophysical, macroscopic and microscopic changes in vitro in porcine skin has been investigated. Fourier transform infrared (FTIR) spectroscopy was employed to investigate the biophysical changes in stratum corneum (SC) lipid and protein. FTIR results showed that the treatment of the SC with JP-8 to increasing exposure time caused correspondingly greater percent decrease in the peak heights and areas under the absorbance curve of methylene and amide absorbances, suggesting greater loss of lipid and protein from SC layers. In vitro transepidermal water loss (TEWL) studies allowed an investigation into the macroscopic barrier properties of the skin. TEWL results were in consonance with that of FTIR. There was a significant increase (P<0.05) in TEWL through 8 and 24 h JP-8 exposed skin in comparison to the control. Light microscopy provided direct, corroborative, visual evidences of epidermal and dermal alterations. Epidermal swelling, dermal matrix granulation, mast cell granules, shortened collagen fibers were observed in the skin exposed with JP-8. Thus, it is concluded that JP-8 exposure causes appreciable biophysical and histological changes along with increased TEWL values in vitro in pig skin which may lead to skin irritation and dermal toxicity in vivo.

Percutaneous absorption, biophysical, and macroscopic barrier properties of porcine skin exposed to major components of JP-8 jet fuel.

JP-8 has been associated with toxicity in animal models and humans. There is a great potential for human exposure to JP-8. Quantitation of percutaneous absorption of JP-8 is necessary for assessment of health hazards involved in its occupational exposure. In this study, we selected three aliphatic (dodecane, tridecane, and tetradecane) and two aromatic (naphthalene and 2-methylnaphthalene) chemicals, which are major components of JP-8. We investigated the changes in skin lipid and protein biophysics, and macroscopic barrier perturbation from dermal exposure of the above five chemicals. Fourier transform infrared (FTIR) spectroscopy was employed to investigate the biophysical changes in stratum corneum (SC) lipid and protein. FTIR results showed that all of the above five components of JP-8 significantly (P<0.05) extracted SC lipid and protein. Macroscopic barrier perturbation was determined by measuring the rate of transepidermal water loss (TEWL). All of the five JP-8 components studied, caused significant (P<0.05) increase in TEWL in comparison to control. We quantified the amount of chemicals absorbed assuming 0.25 m(2) body surface area exposed for 8 h. Our findings suggest that tridecane exhibits greater permeability through skin among aliphatic and naphthalene among aromatic JP-8 components. Amount of chemicals absorbed suggests that tridecane, naphthalene and its methyl derivatives should be monitored for their possible systemic toxicity.

EFFECT OF JP-8 JET FUEL EXPOSURE ON THE ULTRASTRUCTURE OF SKIN

Fuel system maintenance usually requires direct, prolonged exposure to fuel. Thus, both military and commercial aircraft workers are at risk of dermal exposure and toxicity from JP-8 jet fuel. At present, there are no standards for U.S. Air Force personnel regarding dermal exposure to jet fuel. Hence, there are needs for data and approaches to understand the human hazard from dermal exposure to JP-8. In this study, we investigated the alteration in porcine skin at ultrastructural level, after a 24-h exposure to JP-8, with the help of transmission electron microscopy (TEM). Many ultrastructural modifications were noticed in the photomicrographs. Large-scale expansion in intercellular lipid domains of stratum corneum and disruption in its structural integrity; alteration in configuration of basal cells; rupture of hemidesmosomes and desmosomes; and diminished dendritic processes in Langerhans cells were observed. It is concluded that JP-8 exposure can cause alteration in skin anatomy, which may lead to dermal toxicity. Further studies are required to determine comparative damages incurred by individual components of JP-8.

A review of patents on therapeutic potential and delivery of hydrogen sulfide

BACKGROUND Hydrogen sulfide (H2S) is a colorless gas with a characteristic smell of rotten eggs. Once only thought of as a toxic gas, evidence now shows that H2S plays major roles in pathological and physiological activities. These roles are being utilized to treat diseases and disorders ranging from hypertension, inflammation, edema, cardiovascular issues, chronic pain, cancer, and many more. Challenges facing the use of H2S currently involve achieving the optimum therapeutic concentrations, synthesizing chemically and physiologically stable donors, and developing clinically appropriate delivery systems. METHODS We did an extensive literature search on therapeutic potentials and related issues of H2S which were presented in a systematic flow pattern in introduction. Patents accepted/filed on various aspects of hydrogen sulfide were searched using the United States Patent and Trademark Office database at http://patft.uspto.gov/ and google patents at https://patents.google.com/. The important search terms combined with H2S were therapeutic effect, pharmacological action, biochemistry, measurement, and delivery. We also incorporated our own experiences and publications while discussing the delivery approaches and associated challenges. RESULTS In the process, researchers have discovered novel techniques in preparing the noxious gas by discovering and synthesizing H2S donors and developing controlled and predictable delivery systems. Donors utilized thus far include derivatives of anti-inflammatory drugs like H2S -aspirin, Allium sativum extracts, inorganic salts, phosphorodithioate derivatives, and thioaminoacid derivatives. Use of controlled delivery systems for H2S is critical to maintain its physiological stability, optimum therapeutic window, increase patient compliance, and make it easier to manufacture and administer. Numerous patents overcoming the challenges of using H2S therapeutically with various donors and delivery mechanisms have been reviewed. CONCLUSION The scientific knowledge gained from the last decade researches has moved H2S from a foul smelling pungent gas to the status of a gasotransmitter with many potential therapeutic applications. However, developing a suitable donor and a delivery system using that donor for providing precise and sustained release of H2S for an extended period, is critically needed for any further development towards its translation into clinical practices.