PHYSIOCHEMICAL STABILITY AND MASS SPECTROMETRIC ANALYSIS OF GEMINI SURFACTANT-BASED LIPOPLEXES

Cationic lipids have been comprehensively studied as non-viral vectors for gene therapy, focusing on improving the gene transfer efficiency and the safety profile. However, clinical applications of cationic lipid/DNA lipoplexes are restricted due to their low physical stability in aqueous formulations. One specific group of cationic lipids that showed efficient transfection activity is the gemini surfactants. Two main objectives were determined in this work. The first was to evaluate the feasibility of lyophilization as a formulation technique for preparing gemini surfactant-based lipoplexes with long-term stability. The second objective was to establish a universal tandem mass spectrometric “fingerprint” of novel amino acid modified gemini surfactants as a pre-requirement for the identification and quantification of gemini surfactants in different pharmaceutical matrices. In order to investigate the influence of lyophilization on the essential physiochemical properties and the in vitro transfection efficiency of gemini surfactant-lipoplexes, a diquaternary ammonium gemini surfactant (12-7NH-12) and plasmid DNA (pDNA) encoding for interferon-γ (IFNγ) were used to prepare pDNA/gemini surfactant [P/G] lipoplexes. Helper lipid DOPE [L] was incorporated in all formulations producing a [P/G/L] system. Several excipients were utilized as stabilizing agents. Lipoplexes formulated with the cryoprotectant were subjected to a lyophilization/rehydration cycle. Transfection activity was assessed by measuring the level of expressed IFNγ and cellular toxicity (MTT assay). The results showed that the physiochemical properties of gemini surfactant-based lipoplexes were dependent on the nature of the stabilizing agents used to prepare the lipoplexes. Disaccharide sugars, sucrose and trehalose, provided the most efficient cryoprotectant effect based on their ability to physically stabilize the lipoplexes during the lyophilization process. The transfection efficiency of the lyophilized lipoplexes increased 2-3 fold compared to fresh formulations upon lyophilization. This effect can be attributed to the improvement of DNA compaction and changes in the lipoplex morphology due to the lyophilization/rehydration cycles. Based on these results, we evaluated the ability of lyophilization to improve the stability of gemini surfactant-based lipoplexes. Four lyophilized formulations were stored at 25˚C for three months. The formulations were analyzed monthly for physical appearance, physiochemical properties (particle size and zeta potential, pDNA compaction, gemini surfactant:pDNA interaction) and in vitro transfection. The physiochemical properties of the lyophilized formulations were maintained throughout the three month study. All lyophilized formulations showed a loss of gene transfection activity after three months of storage. Nevertheless, no significant losses of transfection efficiency were observed for three formulations after two months storage at 25 ˚C. These findings suggest that lyophilization significantly improved the physiochemical stability of gemini surfactant-based lipoplexes compared to liquid formulations. As well, lyophilization improved the transfection efficiency of gemini surfactant-based lipoplexes. The loss of transfection activity upon storage is most probably due to the conformational changes in the supramolecular structure of the lipoplexes as a function of time and temperature, rather than to DNA degradation. To establish a foundation for employing the mass spectrometric methods in the evaluation of the chemical stability of the gemini surfactant, we evaluated the tandem mass spectrometric (MS/MS) behavior of six amino acid/di-peptide modified gemini surfactants that were synthesized based on the precursor compound 12-7NH-12. This was accomplished by using a hybrid quadrupole orthogonal time-of-flight mass spectrometer (QqToF-MS) and a triple quadrupole linear ion trap mass spectrometer (QqQ-LIT MS) equipped with electrospray ionization (ESI) source. The single stage QqToF-MS data obtained in the positive ion mode verified the molecular composition of all tested gemini surfactants. Tandem mass spectrometric (MS/MS) analysis showed common fragmentation behavior among all tested compounds, allowing for the establishment of a universal fragmentation pattern. The fragmentation pathway was confirmed by MS/MS/MS experiments utilizing a Q-TrapTM 4000 LC/MS/MS system and (MS/MS) analysis of the deuterated form of 12-7N(Glycine)-12 gemini surfactant. Unique product ions, originating from the loss of one or both head groups along with the attached tail region(s), confirmed the chemical structure of the tested compounds. In conclusion, different lyophilization strategies and analytical methods have been established to develop and examine the physiochemical stability of gemini surfactant-based lipoplex. A tandem mass spectrometric fragmentation pathway was established to enable the identification and quantification of these compounds in pharmaceutical formulations

Enhancement of light absorption using Nanoparticles Embedded Double layer Anti-Reflection Coating

The formation of nanoparticles embedded composite materials is a means for engineering the electrical and optical properties of thin films. This paper proposes the use of gold and silver nano-particles(NPs) to fine tune the effective index of two dielectric layers towards anti-reflection coating applications. Here, the upper layer is MgF2 (magnesium fluoride) and the lower layer is PMMA (Polymethylmethacrylate). The effect of embedding the nano-particles in the PMMA layer on the transmission spectrum is studied while tuning the concentration (volume fraction) and size of particles. With the increase in the size of the nano-particles there is a red shift in the transmission dip. On varying the nano-particle size the peak absorption can be shifted to the desired wavelength. Considering 50 nm silver nano-particle with the volume fraction ranging from 0.001 to 0.05, maximum transmission of light is observed under lower wavelength range of visible spectrum across the novel structur

Exploring EFL university learners’ acquisition of advanced reading skills in the Yemeni context

Reading is an essential language skill for enhancing learners’ performance at various levels of study. However, EFL learners at the tertiary level encounter reading difficulties, particularly in acquiring advanced reading skills, which have affected their reading comprehension and resulted in low academic performance achievement. This is probably attributed to various factors, including learners’ lack of effective reading strategies. A study that exclusively explores reading difficulties encountered by EFL university learners, reasons for the difficulties, and strategies adopted to overcome the difficulties and develop advanced reading skills seem to be scarce in the literature. Therefore, the main purpose of this study was to explore the acquisition process of advanced reading skills in EFL tertiary context at a private university in Yemen from learners’ perspective. The study adopted a qualitative approach to gather data from EFL tertiary learners through a focus group discussion. The data were analyzed manually using the indexing approach. Findings revealed that learners face reading difficulties such as inference making, getting the gist of the text, and managing the reading tasks. These difficulties were attributed to linguistic and non-linguistic reasons, and metacognitive, cognitive, and social-affective strategies were used in reading. The study recommends engaging EFL learners in intensive and extensive reading to help them apply the strategies they learn and develop advanced reading skills and better academic performance. Future research studies may focus on strategies for reading fluency

Exploring reflective practice among university English teachers in Yemen: A case study

Reflection is an important teaching tool for teachers in higher education. By reflecting on the teaching performance, teachers can make sense of reflection for professional development and meaningful teaching and learning. Given that beliefs and practices are important components of reflective practice, more in-depth understanding of how teachers engage in reflection needs to be explored. Previous studies mainly focused on teacher‟s beliefs about reflection. However, little is known about how reflection is currently practiced among the university English teachers in Yemen. This study explores how reflection is practiced at one private university in Yemen by employing a qualitative case study method to gain insights into the phenomenon. Data were collected through a multipronged research approach including semi-structured interviews, semistructured classroom observations, journal entry and focus group discussions. Five teachers with ten-years of teaching experience were purposively selected as the key informants. Six to ten students taught by every informant took part in the focus group discussions. Data were analyzed using a coding scheme. The findings indicate that the teachers engaged in various levels, types and patterns of reflection. The multifaceted elements of reflection revealed that teachers‟ reflection was caused by two types of factors namely enabling and constraining factors. The study demonstrates that teachers need to constantly engage in formal, regular and collaborative reflection with students, colleagues, and administrators for professional development. The study provides several implications. Theoretically, the study leads to a critical awareness of the different layers of reflection. Practically, it gives teachers, administrators and decision-makers in-depth information about effective reflective practice, in particular, its process and relevance to teacher education. Methodologically, other studies can employ a similar approach to understand any complex phenomena related to teaching and learning. Further research studies are required to explore the roles of university administrators and policy makers in promoting effective reflection

Updated Management of Atrophic Post Acne Scars: Review Article

Background: Hair follicle and sebaceous gland inflammation causes acne, which is a long-term, chronic skin condition. The androgen-induced sebum overproduction leads to first acne appearance. It is caused by altered and aberrant keratinization, inflammation and the colonization of facial hair follicles by the bacteria Propionibacterium acnes. Acne also has a delayed immune response, as well as influences from the environment and genetics. Treatments for post-acne scarring have included topical preparations such as chemical peels, dermabrasion, laser resurfacing and punch excision and punch elevation, as well as fat transfer, implantation of autologous collagen and cultured and expanded autologous fibroblasts. Other treatments have included trichloroacetic acid focal treatment and skin microneedling to improve the dermal extracellular matrix (ECM) proteins. Objective: To determine the updated treatment modalities in atrophic post-acne scars. Conclusion: In most types of atrophic acne scars combination therapies typically provide superior outcomes than solo treatments

The influence of environmental factors on the effect of market orientation towards business performance of SMEs in Yemen / Waleed Mohammed M. Al-Sabir

SMEs represent the vast majority of establishments in the Arab world and particularly in Yemen, where they represent 99% of the total number of establishments. These establishments lack a deep understanding of the importance of marketing to achieve their goals and continued growth. In addition, there are many SMEs that do not realize the concept of market orientation and how they apply it as one of the concepts of modern marketing that mainly focus on the customer. Furthermore, the supply and demand, forces of competition and the conditions of the market are the basic factors in the Yemeni environment that play a major role in determining to what extent large business companies, in general, are marketoriented companies, and SMEs, in particular, and their influence on the performance of these establishments. This study sought, firstly, to examine whether the relationship established between market orientation and performance in large business firm studies also holds in the context of SMEs in Yemen; and, secondly, to explore the potential effects of market turbulence, technological turbulence, competitive intensity, and market growth on the relationship between market orientation and the performance of SMEs

Development of breast cancer diagnosis system based on fuzzy logic and probabilistic neural network

Breast cancer is one of the most common kinds of cancers that infect females in the whole world. It has happened when the cells in breast tissues start to grow in an uncontrollable way. Because it leads to death, early detection and diagnosis is a very important task to save the patient's life. Due to the restriction of human observers, computer plays a significant role in detecting early cancer signs. The proposed system uses a multi-resolution analysis and a top-hat operation for detecting the suspicious regions in a mammogram image. The discrete wavelet transform feature analysis is utilized for extracting features from the region of interest. Fuzzy Logic (FL) and Probabilistic Neural Network (PNN) are utilized for classifying the tumor into normal or abnormal. The differences between the proposed system and other researches are the use of adaptive threshold value depending on each image, by using Discrete Wavelet Transform (DWT) in both segmentation and feature extraction phases, which decrease complexity and time. Additionally, the detection of more than one tumor in the breast mammogram image and the utilization of FL and PNN work on increasing the system efficiency that led to raising the accuracy rate of the system and reducing the time. The obtained results of accuracy, sensitivity, and specificity were equal to 99 %, 98 %, and 47 %, respectively, and these results showed that the proposed system is more accurate than the other previous related work