PacSurf2016 Session BI-TuP: Biomaterial Surfaces & Interfaces Poster Session

Investigation of crystalline structure and chemistry of biomaterials including biopolymers, bacteria cultures and proteins has always been a great interest for both materials and biomedical communities. The difficulties associated with the imaging of biological structures can be listed as follows: 1) If the imaging is conventional in Scanning / Transmission Electron Microscope (S/TEM), all liquid phase will be evaporated in the vacuum environment when inserted into the microscope, otherwise room temperature fixation, dehydration, infiltration, fixation, embedding and staining should be applied, but in this case, the sample will go through several chemical and thermal processes which involves loss of liquid phase and artificial contrast improvement through preferential staining so that the sample will not be in its native state. 2) If cryogenic imaging is utilized, the sample will be frozen, so all these steps mentioned in 1 will be eliminated. By lowering diffusion rates at liquid nitrogen temperatures, the electron beam induced sample damage will be less, which is good for imaging, but the other energy activated processes, which again depend on the electron beam-sample interaction, are not possible for these frozen samples to occur. 3) In order to see the dynamic processes, in situ fluid cell holders can be used. Even though electron beam related dynamic processes can be visualized with these holders, the sample thickness will be too much including the two silicon nitride windows and the liquid sandwiched in between the windows. 4) To characterize the chemistry and crystal structure knowledge at the native state with the highest resolution, the material needs to be thin and should be sealed/sandwiched in between two single layers of graphene sheets forming graphene liquid cell (GLC), so that the Selected Area Electron Diffraction (SAED) and Electron Energy Loss Spectroscopy (EELS) studies can be carried out in the Cs corrected S/TEMs with the highest resolution available in terms of the crystal structure and chemistry, respectively. We have shown even individual iron ions can be detected in the liquid state when released from the ferritin structures encapsulated in GLC and which proves the necessity of using GLC for the achievement of this sort of resolution [1-2].

[1] T Shokuhfar et al.: High resolution electron microscopy and spectroscopy of ferritin in biocompatible liquid cells and graphene sandwiches, Advanced Materials, 26, 3410, pp. 3410-3414.

[2] The authors acknowledge funding from the National Science Foundation- CAREER award- Grant No- DMR- 1350734.

The objective of this study was to evaluate the effect of an antimicrobial bioactive edible coating on the microbiological quality of ready-to-eat cauliflowers. Combined treatments using antimicrobial coating in combination with a low γ-radiation dose or negative air ionization (NAI) with ozone on the microbiological quality of ready-to-eat cauliflowers was also evaluated. The antimicrobial coating was based on a microemulsion of citrus and lemongrass extract in mixture. The microemulsion was also mixed with a polymeric formulation based on maltodextrin and methylcellulose.

Results showed that each treatment alone was effective on Listeria innocua, Escherichia coli and mesophilic bacteria.

The antimicrobial coating was able to reduce by 2 Log CFU/gr, the level of E. coli and L. innocua and by 1.5 log CFU/gr, the level of total mesophilic bacteria. The bioactive coating acts also in synergy with γ-radiation, inducing no bacterial growth of L. innocua and E. coli, as well as a control of the growth of mesophilic bacteria during 7 days of storage. However, the use of NAI + ozone did not act in synergy with the antimicrobial coating to reduce the level of the pathogens under study. However, storage of coated vegetables under NAI + ozone atmosphere would be a good technique to reduce and control bacterial growth during storage to prevent cross-contamination.

This presentation is about hybrid structures comprising carbon nanomembrane (CNM) as a functional substrate and oriented assembled purple membranes (PMs). CNMs are monomolecular cross-linked layers of aromatic amphiphilic molecules with lateral dimensions of several square centimeters and a thickness of about 1 nm. PM from Halobacterium salinarum is a membrane consisting of bacteriorhodopsin (BR), which is a light-driven proton pump, and lipids.

CNM has already been successfully tested as a substrate for electron cryo-microscopy of PM. To realize the oriented assembly of PM patches on CNM, we used a PM mutant, which has histidine (HIS) tags selectively on one side of the membrane and a nitroliotriacetic acid (NTA) terminated NBPT-CNM. The functionalized CNM has also been tested with different HIS-tagged proteins.

Due to a dramatic change in both the lifestyle and eating habits, a steady increase in risk of gastrointestinal diseases every year. Early detections and treatments can reduce the mortality caused by gastrointestinal diseases. Fecal occult blood (FOB) is a small amount of blood in the stool which is invisible to human eye. If blood is detected in FOB, the cause may be gastrointestinal disorders, such as colorectal polyps, colorectal cancer and, etc. Fecal occult blood test (FOBT) is a rapid and non-invasiveness method for early diagnostics about gastrointestinal diseases. In this study, we present an alternative method for FOBT other than the traditional methods by using the time-of-flight secondary ion mass spectrometry (TOF-SIMS). TOF-SIMS can analyzes the molecular composition of the sample surface with a simple pre-treatment or even without any pre-treatment. Furthermore this method can avoid the potential pitfalls found in the traditional FOBT, such as the false positive results due to the interfere of food and drugs in the chemical method and the false negative responses due to the hemoglobin degradation during the storage in the immunization method. Preliminary results shown that there are significant differences at m / z = 86 and m / z = 184 for the stool samples with FOB. Currently we test different pre-treatments to achieve consistency and accuracy of the experimental results.

Waterborne biodegradable cationic polyurethane (WCPU) nanoparticle dispersion was synthesized by reaction of polycaprolactone, isophorone diisocyanate, and N-methyldiethanolamine under 75 °C and vigorous stirring under acidic condition. The nanoparticles dispersed in the aqueous medium were uniform with an average size of ~80 nm and a zeta potential of ~60 mV. The WCPU nanoparticle dispersion may be cast into films. The contact angle of the films was ~67°and the zeta potential was ~16 mV. The WCPU nanoparticles demonstrated excellent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (100% inhibition with a contact time of 3 h). Meanwhile, the antibacterial ratio of WCPU films to E. coli and S. aureus reached 100% after 24 h of contact. Moreover, The WCPU nanoparticles could be used as a transfection reagent without significant toxicity for concentrations less than 1000 mg/mL and showed the ability to condensate plasmid DNA. The transfection efficiency for HEK293T cells was ~60% after 48 h of transfection. Moreover, the WCPU dispersion can be made into microspheres conveniently. The WCPU dispersion prepared in the study has potential antibacterial and biomedical applications.