Characterizations and Antibacterial Efficacy of Chitosan Oligomers Synthesized by Microwave-Assisted Hydrogen Peroxide Oxidative Depolymerization Method for Infectious Wound Applications.

The use of naturally occurring materials with antibacterial properties has gained a great interest in infected wound management. Despite being an abundant resource in Vietnam, chitosan and its derivatives have not yet been intensively explored for their potential in such application. Here, we utilized a local chitosan source to synthesize chitosan oligomers (OCS) using hydrogen peroxide (H2O2) oxidation under the microwave irradiation method. The effects of H2O2 concentration on the physicochemical properties of OCS were investigated through molecular weight, degree of deacetylation, and heavy metal contamination for optimization of OCS formulation. Then, the antibacterial inhibition was examined; the minimum inhibitory concentration and minimum bactericidal concentration (MIC and MBC) of OCS-based materials were determined against common skin-inhabitant pathogens. The results show that the local Vietnamese chitosan and its derivative OCS possessed high-yield purification while the molecular weight of OCS was inversely proportional and proportional to the concentration of H2O2, respectively. Further, the MIC and MBC of OCS ranged from 3.75 to less than 15 mg/mL and 7.5-15 mg/mL, respectively. Thus, OCS-based materials induce excellent antimicrobial properties and can be attractive for wound dressings and require further investigation.

Fabrication of chitosan oligomer-coated electrospun polycaprolactone membrane for wound dressing application.

Wound dressings are typically used to provide a favorable environment supporting the intricate process of wound healing. This research aims to fabricate and evaluate an electrospun polycaprolactone (EsPCL) membrane coated with various densities of chitosan oligomers (COS) - a biological agent - for application as bioactive wound dressing. Weight calculation was employed to investigate the density of COS coated onto the electrospun PCL membrane. Physicochemical characteristics of the prepared membranes, such as hydrophilicity and mechanical properties were demonstrated and evaluated through standard experimental methods. In vitro assays and mice model were used to investigate the antibacterial activities, cytocompatibility, hemostasis and the in vivo interaction of the membranes. The results showed that COS was coated successfully on the surface of the polymeric membrane, altering its morphology and associated characteristics. The greater concentration of COS led to an increase in the thickness of the membrane, which resulted in stronger antibacterial activities. Moreover, the increase of chitosan oligomers density in the membrane induced faster hemostasis and affected the re-epithelialization and wound healing in mice. Thus, the membrane as a whole and particularly chitosan oligomers were shown to be potential for further studies regarding wound dressing.

Development of a portable electrochemical loop mediated isothermal amplification (LAMP) device for detection of hepatitis B virus.

The objective of this study was to develop a simple, inexpensive prototype device for rapid detection of hepatitis B virus (HBV). The device was able to simultaneously amplify, detect and quantify the target HBV DNA. The system was fabricated from a custom-made electrochemical set-up of which the temperature was thermostatically controlled by a water bath. Real-time monitoring of HBV DNA was accomplished by measuring the response of redox indicator in the reaction mixture. Concentration of HBV DNA in the samples was determined from the peak high ratio (PHR) and threshold time relationship. The signal was processed by sigmoidal model fitting to enhance the accuracy of the results. Key parameters including concentrations of redox indicator and reaction temperatures were optimized. Sensitivity and specificity of the method toward HBV DNA were evaluated. The prototype was capable of real-time amplification and detection of HBV DNA with concentration as low as 6.18 fg µl-1. The test showed high specificity against HBV DNA. The system was also able to detect HBV positive serum directly with simple thermal pretreatment instead of tedious DNA extraction. The electrochemical set-up was compatible with microfluidic platforms and can be readily adapted for efficient and high throughput point-of-care (POC) diagnosis of HBV.

Label-free detection of aflatoxin M1 with electrochemical Fe3O4/polyaniline-based aptasensor.

The selective detection of ultratrace amounts of aflatoxin M1 (AFM1) is extremely important for food safety since it is the most toxic mycotoxin class that is allowed to be present on cow milk with strictly low regulatory levels. In this work, Fe3O4 incorporated polyaniline (Fe3O4/PANi) film has been polymerized on interdigitated electrode (IDE) as sensitive film for AFM1 electrochemical biosensor. The immobilized aptamers as an affinity capture reagent and magnetic nanoparticles for signal amplification element have been employed in the sensing platform. Label-free and direct detection of the aptamer-AFM1 on Fe3O4/PANi interface were performed via electrochemical signal change, acquired by cyclic and square wave voltammetries. With a simplified strategy, this electrochemical aptasensor shows a good sensitivity to AFM1 in the range of 6-60 ng·L(-1), with the detection limit of 1.98 ng·L(-1). The results open up the path for designing cost effective aptasensors for other biomedical applications.

Modified interdigitated arrays by novel poly(1,8-diaminonaphthalene)/carbon nanotubes composite for selective detection of mercury(II).

This study describes a novel type of interdigitated arrays (IDA), microfabricated by electropolymerizing structured Poly(1,8-diaminonaphthalene)/functionalized multi-walled carbon nanotubes (PDAN/CNT) thin film onto a silicon chip for square wave voltammetry (SWV) multi-element heavy metal ion detection. The structure of PDAN/CNT was characterized by Raman, FE-SEM and AFM techniques. Analysed experiments reveal that the uptake of Hg(2+) by PDAN/CNT is quite specific and it can be used advantageously for electrochemical sensing of Hg(2+) thanks to original feature of (Hg(2+)/Hg(2)(2+)) redox potential with the respect to that of PDAN/CNT. As-developed IDA type electrode can extend its utility in other sensing applications.

Development of interdigitated arrays coated with functional polyaniline/MWCNT for electrochemical biodetection: application for human papilloma virus.

In this study, polyaniline-multiwalled carbon nanotube film (PANi-MWCNT) has been polymerized on interdigitated platinum electrode arrays (IDA), fabricated by MEMS technology for the detection of human papillomavirus (HPV) infection, using immobilized peptide aptamers as affinity capture reagent. Label-free, electrochemical detection of the specific immune reaction between antigen peptide aptamer HPV-16-L1 (with a molecular weight of 1825 Da), the most common genotype in cytological normal women worldwide, and its specific antibody of HPV-16 (which is much bigger with molecular weight of ca. 150 kDa) on multifunctional PANi-MWCNT based arrays was reported. The most significant advantage of this technique consists of reagentless and multiple detection of antigen-antibody complex formation on well conducting IDA interface of PANi-MWCNT, without intermediate steps or any labeling reagents, as normally required in the previous works.

Preparation of chitosan/magnetite composite beads and their application for removal of Pb(II) and Ni(II) from aqueous solution.

A simple and effective process has been proposed to prepare chitosan/magnetite nanocomposite beads with saturation magnetization value as high as uncoated Fe3O4 nanoparticles (ca. 54emu/g). The reason was that the coating chitosan layer was so thin that it did not affect magnetic properties of these composite beads. Especially, chitosan on the surface of the magnetic Fe3O4 nanoparticles is available for coordinating with heavy metal ions, making those ions removed with the assistance of external magnets. Maximum adsorption capacities for Pb(II) and Ni(II), occurred at pH 6 and under room temperature were as high as 63.33 and 52.55mg/g respectively, according to Langmuir isotherm model. These results permitted to conclude that chitosan/magnetite nanocomposite beads could serve as a promising adsorbent not only for Pb(II) and Ni(II) (pH=4-6) but also for other heavy metal ions in wastewater treatment technology.