Mong-Chuan Lee

Wide Host Range and Strong Lytic Activity of Staphylococcus aureus Lytic Phage Stau2

ABSTRACT In searching for an alternative antibacterial agent against multidrug-resistant Staphylococcus aureus, we have isolated and characterized a lytic staphylophage, Stau2. It possesses a double-stranded DNA genome estimated to be about 134.5 kb and a morphology resembling that of members of the family Myoviridae. With an estimated latency period of 25 min and a burst size of 100 PFU/infected cell, propagation of Stau2 in liquid culture gave a lysate of ca. 6 × 1010 PFU/ml. It was stable at pH 5 to 13 in normal saline at room temperature for at least 4 weeks and at −85°C for more than 2 years, while 1 × 109 out of 2 × 1012 PFU/ml retained infectivity after 36 months at 4°C. Stau2 could lyse 80% of the S. aureus isolates (164/205) obtained from hospitals in Taiwan, with complete lysis of most of the isolates tested within 3 h; however, it was an S. aureus-specific phage because no lytic infection could be found in the coagulase-negative staphylococci tested. Its host range among S. aureus isolates was wider than that of polyvalent phage K (47%), which can also lyse many other staphylococcal species. Experiments with mice demonstrated that Stau2 could provide 100% protection from lethal infection when a multiplicity of infection of 10 was administered immediately after a challenge with S. aureus S23. Considering these results, Stau2 could be considered at least as a candidate for topical phage therapy or an additive in the food industry.

Highly Absorbent Antibacterial Hemostatic Dressing for Healing Severe Hemorrhagic Wounds

To accelerate healing of severe hemorrhagic wounds, a novel highly absorbent hemostatic dressing composed of a Tencel®/absorbent-cotton/polylactic acid nonwoven base and chitosan/nanosilver antibacterial agent was fabricated by using a nonwoven processing technique and a freeze-drying technique. This study is the first to investigate the wicking and water-absorbing properties of a nonwoven base by measuring the vertical wicking height and water absorption ratio. Moreover, blood agglutination and hemostatic second tests were conducted to evaluate the hemostatic performance of the resultant wound dressing. The blending ratio of fibers, areal weight, punching density, and fiber orientation, all significantly influenced the vertical moisture wicking property. However, only the first two parameters markedly affected the water absorption ratio. After the nonwoven base absorbed blood, scanning electron microscope (SEM) observation showed that erythrocytes were trapped between the fibrin/clot network and nonwoven fibers when coagulation pathways were activated. Prothrombin time (PT) and activated partial thromboplastin time (APTT) blood agglutination of the resultant dressing decreased to 14.34 and 50.94 s, respectively. In the femoral artery of the rate bleeding model, hemostatic time was saved by 87.2% compared with that of cotton cloth. Therefore, the resultant antibacterial wound dressing demonstrated greater water and blood absorption, as well as hemostatic performance, than the commercially available cotton cloth, especially for healing severe hemorrhagic wounds.

Efficacy of Mastoparan-AF alone and in combination with clinically used antibiotics on nosocomial multidrug-resistant Acinetobacter baumannii

Emergence of multidrug-resistant Acinetobacter baumannii (MDRAB) has become a critical clinical problem worldwide and limited therapeutic options for infectious diseases caused by MDRAB. Therefore, there is an urgent need for the development of new antimicrobial agents or alternative therapy to combat MDRAB infection. The aim of this study was to investigate effects of Mastoparan-AF (MP-AF), an amphipathic peptide isolated from the hornet venom of Vespa affinis with broad-spectrum antimicrobial activity, on MDRAB. As compared with clinical used antibiotics, MP-AF exhibited potent antimicrobial activity at 2–16 μg/ml against the reference strain A. baumannii ATCC 15151 and seven MDRAB clinical isolates, especially the colistin-resistant MDRAB, E0158. The synergistic antimicrobial combination study revealed that MP-AF acted synergistically with specific antibiotics, e.g., ciprofloxacin, trimethoprim/sulfamethoxazole (SXT) or colistin against some isolates of the MDRAB. It was noteworthy when MP-AF combined with SXT exhibited synergistic activity against all SXT-resistant MDRAB isolates. The synergistic combination of MP-AF and antibiotics could reduce the dosage recommended of each antimicrobial agent and improve the safety of medications with ignorable adverse effects, such as colistin with nephrotoxicity in therapeutic dose. Furthermore, MP-AF combined with antibiotics with different antimicrobial mechanisms could reduce selective pressure of antibiotics on bacteria and prevent the emergence of antimicrobial-resistant strains. Importantly, we are the first finding that MP-AF could make MDRAB from the original non-susceptibility to SXT become sensitivity. In conclusion, MP-AF alone or in combination with other antibiotics, especially SXT, is a potential candidate against MDRAB infection in clinical medicine.

Recovery evaluation of rats' damaged tibias: Implantation of core-shell structured bone scaffolds made using hollow braids and a freeze-thawing process

This study prepares biodegradable bone scaffolds helping the recovery of damaged tibias of rats. Polyvinyl alcohol (PVA) plied yarns are fabricated into hollow braids. The braids are combined with hydroxyapatite (HA)/gelatin/PVA mixtures and processed using freeze-thawing and freeze-drying processes in order to form bone scaffolds. These bone scaffolds are observed by scanning electron scope (SEM) and tested for compression strength. Afterwards, recovery of damaged bone, the morphology of the bone, and the histological observation are evaluated. Results indicate a small amount of HA helps in enhancing the compressive strength of bone scaffolds. Results of in vivo assay indicate the damaged tibias of rats recover and function well eight weeks after the implantation, and exhibit a normal morphology. Histological observation confirms the bone scaffolds gradually decompose, allowing tissue infiltration and facilitating ossification. This study successfully produces bone scaffolds with satisfactory mechanical properties helping in the recovery of damaged tibias of rats.

Polylactic acid/carbon fiber composites: Effects of polylactic acid-g-maleic anhydride on mechanical properties, thermal behavior, surface compatibility, and electrical characteristics

This study uses a reactive extrusion for the grafting of maleic anhydride on polylactic acid in order to form polylactic acid grafted maleic anhydride that serves as a compatibilizer between polylactic acid and carbon fiber. The effects of different ratios of the free radical initiator to maleic anhydride as well as the amounts of polylactic acid grafted maleic anhydride on the mechanical properties, interfacial compatibility, thermal behaviors, and electrical properties of the polylactic acid/carbon fiber composites are discussed. The test results indicate that using polylactic acid grafted maleic anhydride as compatibilizer improves the interfacial compatibility of polylactic acid/carbon fiber composites, which in turn contributes to a high electrical conductivity and the electromagnetic interference shielding effectiveness, while decreasing the surface resistance and increases. In addition, the amount of polylactic acid grafted maleic anhydride has a positive influence on their tensile properties, flexural strength, and impact strength. The differential scanning calorimetry results indicate that a high polylactic acid grafted maleic anhydride content is also conducive to crystallinity, but is not in related to the melting temperature. According to the scanning electronic microscope observation, the fractured composites that are inflicted by an impact have considerably few traces of the fibers being pulled out, which is ascribed to polylactic acid that can completely enwrap carbon fiber. Therefore, the incorporation of polylactic acid grafted maleic anhydride is proven to strengthen polylactic acid/carbon fiber composites, exemplified by their improved interfacial compatibility and properties.

Three-dimensional Porous Polylactic Acid Bone Scaffolds: Web Lamination Techniques and Property Evaluations

This study aims at producing three-dimensional porous polylactic acid (PLA) bone scaffolds using a web manufacturing. Webs are laminated and are then processed with heat treatment in order to form low *melting point PLA porous bone scaffolds. A stereomicroscope, a scanning electron microscope, the pore size measurement, porosity, and compression test are used in order to evaluate the bone scaffolds. The test results indicate that regardless of the temperatures of heat treatment, all PLA porous bone scaffolds have interconnected pores. An increasing temperature of treatment causes the pore size to decrease from 160μm to 100μm and mechanically improves the bond scaffolds. Therefore, this study successfully creates porous bone scaffolds made of low melting point point PLA and web lamination techniques.

A Study on the Repellent Efficacy of Essential Oils Against Forcipomyia Taiwana

The majority of commercially available mosquito repellents contains N, N-diethyl-3-methylbenzamide compound (DETT). The long term uses of DETT have a negative influence on the nervous and *immune systems. Therefore, the development of mosquito repellents that are DETT-free is important. In this study, essential oils of lavandula angustifolia, Melaleuca Alternifolia, Mentha piperita, Eucalyptus globules, and Eucalyptus citriodora are evaluated in terms of the repellent efficacy against F. taiwana by using a Y-tube olfactometer test. Their repellent efficacy is then compared. The combination of 200 μl lavandula angustifolia and Eucalyptus citriodora attains a repellent efficacy of 70% and 65%, respectively. Conversely, using Melaleuca Alternifolia, Mentha piperita, and Eucalyptus globules does not result in any significant repellence against F. taiwana, which may be ascribed to the high concentration. When 1μl of these essential oils are added, they have a repellent efficacy of 61-65%. The repellent efficacy of different essential oils is ranked as Eucalyptus globules>Mentha piperita = Melaleuca Alternifolia> lavandula angustifolia> Eucalyptus citriodora.

Influential Factors on Formation of Nanofibers: Assessments of Electrostatic Spinning Parameters

Nanofibers have a high specific surface area and a high porosity, and thus have been applied to many fields. Electrostatic spinning is one efficient and convenient method for the preparation of nanofibers. Two influential factors of the formation of nanofibers include processing parameters, such as voltages and velocity, and environmental factors, such as temperatures and humidity. This study uses a home-made electrospinning machine for the production. The morphology of the resulted nanofibers is examined in terms of the processing parameters, in order to provide f more feasible applications. The test results indicate that the viscosity of PVA electrospinning solution becomes dense as a result of the increasing temperatures. An increasing voltage changes the morphology of nanofibers from being smooth to rugged. Moreover, the diameter of nanofibers becomes smaller when the electrospinning distance is increased. *

Porous Tubular PVA Hydrogels: Preparation and Assessment

Hydrogels have been used in related biomedical fields, and their pore size and structure are an important investigation emphasis in relative studies. Hydrogels with different pore sizes have different applications. This study aims to examine the pore size and porosity of the polyvinyl alcohol (PVA) tubular hydrogels. Sodium chloride (NaCl) with different concentrations serves as the porogen while polyvinylpyrrolidone (PVP) serves as the surfactant. PVA is made into tubular hydrogels via a freeze-thaw method and the cross-linking with glutaraldehyde. The hydrogels are then processed with an ultrasonic vibration in order to remove the residual solvents and the porogens, in order to obtain tubular PVA hydrogels with an interconnected porous structure. The test results indicate that the porosity and pore size of the PVA hydrogels significantly increase as a result of the uses of a porogen. Excessive NaCl as a porogen damages the porous structure of hydrogels, which in turn decreases the porosity and pore size of the hydrogels.