Santina Carnazza | University of Messina (original) (raw)

Papers by Santina Carnazza

The early diagnosis of malignancy is the most critical factor for patient survival and the treatm... more The early diagnosis of malignancy is the most critical factor for patient survival and the treatment of cancer. In particular, leukemic cells are highly heterogeneous, and there is a need to develop new rapid and accurate detection systems for early diagnosis and monitoring of minimal residual disease. This study reports the utilization of molecular networks consisting of entire bacteriophage structure, displaying specific peptides, directly assembled with silver nanoparticles as a new Surface Enhanced Raman Spectroscopy (SERS) probe for U937 cells identification in vitro. A 9-mer pVIII M13 phage display library is screened against U937 to identify peptides that selectively recognize these cells. Then, phage clone is assembled with silver nanoparticles and the resulting network is used to obtain a SERS signal on cell-type specific molecular targets. The proposed strategy could be a very sensitive tool for the design of biosensors for highly specific and selective identification of hematological cancer cells and for detection of minimal residual disease in a significant proportion of human blood malignancy.

Several foodborne human pathogens, when exposed to harsh conditions, enter viable but nonculturab... more Several foodborne human pathogens, when exposed to harsh conditions, enter viable but nonculturable (VBNC) state; however, still open is the question whether VBNC pathogens could be a risk for public health, because, potentially, they can resuscitate. Moreover, cultural methods for food safety control were not able to detect VBNC forms of foodborne bacteria. Particularly, it has not been established whether food chemophysical characteristics can induce VBNC state in contaminating pathogen bacterial populations, especially in food, such as salads and fresh fruit juices, not subjected to any decontamination treatment. In this preliminary study, we intentionally contaminated grapefruit juice to determine whether pathogen bacteria could enter VNBC state. In fact, grapefruit juice contains natural antimicrobial compounds, has an average pH of about 3 and low content in carbohydrates. Such characteristics make grapefruit juice a harsh environment for microbial survival. For this purpose, Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium ATCC 14028, Listeria monocytogenes ATCC 7644, and Shigella flexneri ATCC 12022, at two different inoculum sizes, have been used. Viability by the LIVE=DEAD BacLight Bacterial Viability kit and culturability by plate counts assay were monitored, whereas ''resuscitation'' of nonculturable populations was attempted by inoculation in nutrient-rich media. The data showed that L. monocytogenes lost both culturability and viability and did not resuscitate within 24 h independently on inoculum size, whereas E. coli O157:H7 was able to resuscitate after 24 h but did not after 48 h. Salmonella Typhimurium and S. flexneri, depending on inoculum size, lost culturability but maintained viability and were able to resuscitate; moreover, S. flexneri was still able to form colonies after 48 h at high inoculum size. In conclusion, entry into VBNC state differs on the species, depending, in turn, on inoculum size and time of incubation.

Pseudomonas aeruginosa is an ubiquitous bacterium that, due to its high metabolic versatility, is... more Pseudomonas aeruginosa is an ubiquitous bacterium that, due to its high metabolic versatility, is able to persist for prolonged periods of time. It is the ethiological agent of cystic fibrosis and is involved in urinary infections, conjunctivitis, otitis and pneumonia. We present the results of a batch culture of P. aeruginosa inoculated in LB medium and monitored weekly for a period of 24 months during which no more nutrients are added. A mathematical model suitable to describe the experimental viability data is given.

Biosensors and Bioelectronics, 2015

The early diagnosis of malignancy is the most critical factor for patient survival and the treatm... more The early diagnosis of malignancy is the most critical factor for patient survival and the treatment of cancer. In particular, leukemic cells are highly heterogeneous, and there is a need to develop new rapid and accurate detection systems for early diagnosis and monitoring of minimal residual disease. This study reports the utilization of molecular networks consisting of entire bacteriophage structure, displaying specific peptides, directly assembled with silver nanoparticles as a new Surface Enhanced Raman Spectroscopy (SERS) probe for U937 cells identification in vitro. A 9-mer pVIII M13 phage display library is screened against U937 to identify peptides that selectively recognize these cells. Then, phage clone is assembled with silver nanoparticles and the resulting network is used to obtain a SERS signal on celltype specific molecular targets. The proposed strategy could be a very sensitive tool for the design of biosensors for highly specific and selective identification of hematological cancer cells and for detection of minimal residual disease in a significant proportion of human blood malignancy.

Waves and Stability in Continuous Media - Proceedings of the 14th Conference on WASCOM 2007, 2008

Pseudomonas aeruginosa is an ubiquitous bacterium that, due to its high metabolic versatility, is... more Pseudomonas aeruginosa is an ubiquitous bacterium that, due to its high metabolic versatility, is able to persist for prolonged periods of time. It is the ethiological agent of cystic fibrosis and is involved in urinary infections, conjunctivitis, otitis and pneumonia. We present the results of a batch culture of P. aeruginosa inoculated in LB medium and monitored weekly for a

Nanoparticles and Nanodevices in Biological Applications, 2009

... Biomedical micro-and nanodevices have potential uses that range from the analysis of ... Poly... more ... Biomedical micro-and nanodevices have potential uses that range from the analysis of ... Polymer and hydrogel-based microdevices have many attractive fea-tures for use in ... diagnostic devices for intelligent and integrated sensing with therapeutic mi-cro/nanoscale technologies ...

Journal of Physics: Condensed Matter, 2006

Journal of Physics: Condensed Matter, 2007

Monitoring of food and environmental samples for biological threats, such as Listeria monocytogen... more Monitoring of food and environmental samples for biological threats, such as Listeria monocytogenes, requires probes that specifically bind biological agents and ensure their immediate and efficient detection. There is a need for robust and inexpensive affinity probes as an alternative to antibodies. These probes may be recruited from random peptide libraries displayed on filamentous phage. In this study, we selected from two phage peptide libraries phage clones displaying peptides capable of specific and strong binding to the L. monocytogenes cell surface. The ability of isolated phage clones to interact specifically with L. monocytogenes was demonstrated using enzymelinked immunosorbent assay (ELISA) and confirmed by co-precipitation assay. We also assessed the sensitivity of phage-bacteria binding by PCR on phage-captured Listeria cells, which could be detected at a concentration of 10 4 cells ml −1 . In addition, as proof-of-concept, we tested the possibility of immobilizing the affinity-selected phages to a putative biosensor surface. The quality of phage deposition was monitored by ELISA and fluorescent microscopy. Phage-bacterial binding was confirmed by high power optical phase contrast microscopy. Overall, the results of this work validate the concept of affinity-selected recombinant filamentous phages as probes for detecting and monitoring bacterial agents under any conditions that warrant their recognition, including in food products.

International Journal of Biological Macromolecules, 2001

In this study, we investigated the ability of Pseudomonas aeruginosa ATCC 27853 to grow and synth... more In this study, we investigated the ability of Pseudomonas aeruginosa ATCC 27853 to grow and synthesize poly(3-hydroxyalkanoates) (PHAs) from saturated fatty acids with an even number of carbon atoms, from eight to 22, and from oleic acid. In a non-limiting medium, all carbon sources but docosanoic acid supported cell growth and PHA production, with eicosanoic acid giving the highest yield. In magnesium-limiting conditions, higher yields were obtained from sources with up to 16 carbon atoms. Composition was estimated by gas chromatography of methanolyzed samples and 13 C nuclear magnetic resonance. The 3-hydroxyalkanoate units extended from hexanoate to tetradecanoate or tetradecenoate, with octanoate and decanoate as the predominant components. Weight average molecular weights ranged from 78 000 to 316 000. Fast atom bombardment mass spectrometry of partially pyrolyzed samples, coupled to statistical analysis, showed that these PHAs are random copolymers.

The ability of Pseudomonas aeruginosa ATCC 27853 to grow and synthesize polyhydroxyalkanoates (PH... more The ability of Pseudomonas aeruginosa ATCC 27853 to grow and synthesize polyhydroxyalkanoates (PHAs) using Tween 20 as the sole carbon source was investigated. Tween 20 could support cell growth and PHA production. The polymer produced from Tween 20 was compared with those produced from its major free fatty acids components: lauric (C12), myristic (C14), and palmitic (C16) acids. Gas-chromatographic analysis

Foodborne Pathogens and Disease, 2011

Several foodborne human pathogens, when exposed to harsh conditions, enter viable but nonculturab... more Several foodborne human pathogens, when exposed to harsh conditions, enter viable but nonculturable (VBNC) state; however, still open is the question whether VBNC pathogens could be a risk for public health, because, potentially, they can resuscitate. Moreover, cultural methods for food safety control were not able to detect VBNC forms of foodborne bacteria. Particularly, it has not been established whether food chemophysical characteristics can induce VBNC state in contaminating pathogen bacterial populations, especially in food, such as salads and fresh fruit juices, not subjected to any decontamination treatment. In this preliminary study, we intentionally contaminated grapefruit juice to determine whether pathogen bacteria could enter VNBC state. In fact, grapefruit juice contains natural antimicrobial compounds, has an average pH of about 3 and low content in carbohydrates. Such characteristics make grapefruit juice a harsh environment for microbial survival. For this purpose, Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium ATCC 14028, Listeria monocytogenes ATCC 7644, and Shigella flexneri ATCC 12022, at two different inoculum sizes, have been used. Viability by the LIVE=DEAD BacLight Bacterial Viability kit and culturability by plate counts assay were monitored, whereas ''resuscitation'' of nonculturable populations was attempted by inoculation in nutrient-rich media. The data showed that L. monocytogenes lost both culturability and viability and did not resuscitate within 24 h independently on inoculum size, whereas E. coli O157:H7 was able to resuscitate after 24 h but did not after 48 h. Salmonella Typhimurium and S. flexneri, depending on inoculum size, lost culturability but maintained viability and were able to resuscitate; moreover, S. flexneri was still able to form colonies after 48 h at high inoculum size. In conclusion, entry into VBNC state differs on the species, depending, in turn, on inoculum size and time of incubation.

Biosensors and Bioelectronics, 2008

The design of novel biosensors for the detection of biological threats, such as Pseudomonas aerug... more The design of novel biosensors for the detection of biological threats, such as Pseudomonas aeruginosa, requires probes that specifically bind biological agents and insure their immediate and efficient recognition. Advanced bio-selective sensors may meet the requests for isolation, concentration of the agents and their real-time detection. There is a need for robust and inexpensive affinity probes alternative to antibodies. These probes may be recruited from random peptide libraries displayed on filamentous phage. In this study, we identified from two phage-displayed random peptide libraries phage clones displaying peptides capable of specific and strong binding to P. aeruginosa cell surface. The ability of the phage clones to interact specifically with P. aeruginosa was demonstrated by using enzyme-linked immunosorbent assay (ELISA). We assessed selectivity of phage-bacteria-binding by comparing the binding ability of the selected clones to the selector bacterium and a panel of other bacterial species; we also demonstrated by dot spot and immunoblotting that the most reactive and selective phage peptide bound with high avidity the bacterial cell surface. In addition, as proof-of-concept, we tested the possibility to immobilize the affinity-selected phage to a putative biosensor surface. The quality of phage deposition was monitored by ELISA, and phage-bacterial-binding was confirmed by high-power optical phase contrast microscopy. Overall, the results of this work validate the concept of affinity-selected recombinant filamentous phages as probes for detecting and monitoring bacterial agents under any conditions that warrant their recognition, including clinical-based diagnostics and possibly biological warfare applications.

Biomacromolecules, 2004

Pseudomonas aeruginosa ATCC 27853 accumulated poly(3-hydroxyalkanoates) (PHAs) after growth on sa... more Pseudomonas aeruginosa ATCC 27853 accumulated poly(3-hydroxyalkanoates) (PHAs) after growth on saturated fatty acids with an odd number of carbon atoms. No nutrient limitation was required to induce PHA synthesis, although better yields were obtained when the medium was magnesium deprived. A comparative study was carried out between PHAs obtained from C-odd and those from C-even carbon sources. Repeating units identification was performed by gas chromatography (GC) and capillary liquid chromatography-electrospray mass spectrometry (LC-ESI MS) of methanolyzed samples. When C-odd n-alkanoic acids from nonanoic to pentadecanoic were used the lowest hydroxyalkanoate unit found was 3-hydroxyvalerate and the highest 3-hydroxypentadecanoate, whereas when C-even acids from octanoic to eicosanoic were used these were 3-hydroxycaproate and 3-hydroxyeicosanoate, respectively. Weight average molecular weights were in the range 187 000-596 000. DSC traces showed Tm and DeltaHm which varied from 43 to 58 degrees C and from 5.9 to 24.8 J/g, with the PHAs generated from C-odd carbon sources having lower values. ESI MS of partially pyrolyzed samples allowed the identification of oligomers up to heptamers, and statistical analysis of the ions intensity in the mass spectra showed that these PHAs are random copolyesters.

2004 IEEE International Symposium on Circuits and Systems (IEEE Cat. No.04CH37512), 2004

Bacterial adhesion on surfaces is a very important complex phenomenon, since it is a determinant ... more Bacterial adhesion on surfaces is a very important complex phenomenon, since it is a determinant for the overall biofilm formation; the presence of biofilm can be both beneficial (i.e. to degrade hazardous substances in the soil or in a bioreactor) or detrimental (as on food, ship hulls and biomaterials implants or in the oral cavity). This work starts from a

Bacterial adhesion on surfaces is a very important complex phenomenon, since it is a determinant ... more Bacterial adhesion on surfaces is a very important complex phenomenon, since it is a determinant for the overall biofilm formation; the presence of biofilm can be both beneficial (i.e. to degrade hazardous substances in the soil or in a bioreactor) or detrimental (as on food, ship hulls and biomaterials implants or in the oral cavity). This work starts from a

Mathematical Biosciences and Engineering, 2008

In this work, aggregation states of bacteria on engineered surfaces are investigated both from th... more In this work, aggregation states of bacteria on engineered surfaces are investigated both from the experimental point of view and from the theoretical one. The starting point of this work is a series of experiments carried out on abiotic surfaces in which bacteria adhere forming self-organized patterns. To reproduce the main characteristics of the phenomenon a model based on self-organization of a group of agents has been used. The agents represent bacteria and are free to move on a given surface. On the basis of local rules they may adhere and then eventually form self-organized aggregates. Our numerical results demonstrate that few simple rules are able to explain the emergence of self-organized patterns. Depending on the parameters used, the model is able to reproduce the aggregation patterns observed under different experimental conditions and to predict the behavior of a culture of two bacterial species.

Langmuir, 2002

... Sperone, 31, Vill. S.Agata, 98166 Messina, Italy. Langmuir , 2002, 18 (24), pp 9469–9475. DOI... more ... Sperone, 31, Vill. S.Agata, 98166 Messina, Italy. Langmuir , 2002, 18 (24), pp 9469–9475. DOI: 10.1021/la025800x. Publication Date (Web): October 24, 2002. Copyright © 2002 American Chemical Society. Abstract. This paper reports ...

Surface and Interface Analysis, 2010

ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging has been shown to be a... more ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging has been shown to be a useful tool to study cell adhesion onto a surface. The purpose of this work was that of investigating by means of ToF-SIMS imaging the influence of different salt environments on the adhesion and self organization of Staphylococcus epidermidis ATCC 12228 onto a nonleaching surface (native silicon oxide). Chemical maps show that the different media influence the distribution of bacteria and that their different surface organization in different media is accompanied by characteristic distributions of alkali ions and organic fragments related to the bacteria. This could help in understanding the mechanisms involved in self organization of bacteria, that are thought to be related with the ability of bacteria to modify, by means of ionic fluxes through the cell membrane, the electrostatic interactions that, in turn, appear to rule their self organization in fractal patterns. Copyright © 2010 John Wiley & Sons, Ltd.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003

The paper reports evidence of the different cytocompatibility towards ion irradiated polymer surf... more The paper reports evidence of the different cytocompatibility towards ion irradiated polymer surfaces. In particular, we studied the cell attachment, adhesion and spreading of normal human dermal fibroblast cells onto poly(hydroxymethylsiloxane) and poly(ethyleneterephthalate) surfaces modified by 50 keV Ar þ beams. The cell response is discussed in connection with the radiation-induced changes of the polymers surface chemical structure and related surface free energy, investigated by means of X-ray photoelectron spectroscopy and static contact angle measurements.

Journal of Adhesion Science and Technology, 2011

Microbial adhesion and retention on surfaces are complex phenomena, critical to the formation and... more Microbial adhesion and retention on surfaces are complex phenomena, critical to the formation and development of biofilms. Recently, the focus of research has been more and more on the importance of retention of bacteria under fluctuating high shear forces in biofilm formation. The aim of the present work was to carry out a comparative study of the retention process of

The early diagnosis of malignancy is the most critical factor for patient survival and the treatm... more The early diagnosis of malignancy is the most critical factor for patient survival and the treatment of cancer. In particular, leukemic cells are highly heterogeneous, and there is a need to develop new rapid and accurate detection systems for early diagnosis and monitoring of minimal residual disease. This study reports the utilization of molecular networks consisting of entire bacteriophage structure, displaying specific peptides, directly assembled with silver nanoparticles as a new Surface Enhanced Raman Spectroscopy (SERS) probe for U937 cells identification in vitro. A 9-mer pVIII M13 phage display library is screened against U937 to identify peptides that selectively recognize these cells. Then, phage clone is assembled with silver nanoparticles and the resulting network is used to obtain a SERS signal on cell-type specific molecular targets. The proposed strategy could be a very sensitive tool for the design of biosensors for highly specific and selective identification of hematological cancer cells and for detection of minimal residual disease in a significant proportion of human blood malignancy.

Several foodborne human pathogens, when exposed to harsh conditions, enter viable but nonculturab... more Several foodborne human pathogens, when exposed to harsh conditions, enter viable but nonculturable (VBNC) state; however, still open is the question whether VBNC pathogens could be a risk for public health, because, potentially, they can resuscitate. Moreover, cultural methods for food safety control were not able to detect VBNC forms of foodborne bacteria. Particularly, it has not been established whether food chemophysical characteristics can induce VBNC state in contaminating pathogen bacterial populations, especially in food, such as salads and fresh fruit juices, not subjected to any decontamination treatment. In this preliminary study, we intentionally contaminated grapefruit juice to determine whether pathogen bacteria could enter VNBC state. In fact, grapefruit juice contains natural antimicrobial compounds, has an average pH of about 3 and low content in carbohydrates. Such characteristics make grapefruit juice a harsh environment for microbial survival. For this purpose, Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium ATCC 14028, Listeria monocytogenes ATCC 7644, and Shigella flexneri ATCC 12022, at two different inoculum sizes, have been used. Viability by the LIVE=DEAD BacLight Bacterial Viability kit and culturability by plate counts assay were monitored, whereas ''resuscitation'' of nonculturable populations was attempted by inoculation in nutrient-rich media. The data showed that L. monocytogenes lost both culturability and viability and did not resuscitate within 24 h independently on inoculum size, whereas E. coli O157:H7 was able to resuscitate after 24 h but did not after 48 h. Salmonella Typhimurium and S. flexneri, depending on inoculum size, lost culturability but maintained viability and were able to resuscitate; moreover, S. flexneri was still able to form colonies after 48 h at high inoculum size. In conclusion, entry into VBNC state differs on the species, depending, in turn, on inoculum size and time of incubation.

Pseudomonas aeruginosa is an ubiquitous bacterium that, due to its high metabolic versatility, is... more Pseudomonas aeruginosa is an ubiquitous bacterium that, due to its high metabolic versatility, is able to persist for prolonged periods of time. It is the ethiological agent of cystic fibrosis and is involved in urinary infections, conjunctivitis, otitis and pneumonia. We present the results of a batch culture of P. aeruginosa inoculated in LB medium and monitored weekly for a period of 24 months during which no more nutrients are added. A mathematical model suitable to describe the experimental viability data is given.

Biosensors and Bioelectronics, 2015

The early diagnosis of malignancy is the most critical factor for patient survival and the treatm... more The early diagnosis of malignancy is the most critical factor for patient survival and the treatment of cancer. In particular, leukemic cells are highly heterogeneous, and there is a need to develop new rapid and accurate detection systems for early diagnosis and monitoring of minimal residual disease. This study reports the utilization of molecular networks consisting of entire bacteriophage structure, displaying specific peptides, directly assembled with silver nanoparticles as a new Surface Enhanced Raman Spectroscopy (SERS) probe for U937 cells identification in vitro. A 9-mer pVIII M13 phage display library is screened against U937 to identify peptides that selectively recognize these cells. Then, phage clone is assembled with silver nanoparticles and the resulting network is used to obtain a SERS signal on celltype specific molecular targets. The proposed strategy could be a very sensitive tool for the design of biosensors for highly specific and selective identification of hematological cancer cells and for detection of minimal residual disease in a significant proportion of human blood malignancy.

Waves and Stability in Continuous Media - Proceedings of the 14th Conference on WASCOM 2007, 2008

Pseudomonas aeruginosa is an ubiquitous bacterium that, due to its high metabolic versatility, is... more Pseudomonas aeruginosa is an ubiquitous bacterium that, due to its high metabolic versatility, is able to persist for prolonged periods of time. It is the ethiological agent of cystic fibrosis and is involved in urinary infections, conjunctivitis, otitis and pneumonia. We present the results of a batch culture of P. aeruginosa inoculated in LB medium and monitored weekly for a

Nanoparticles and Nanodevices in Biological Applications, 2009

... Biomedical micro-and nanodevices have potential uses that range from the analysis of ... Poly... more ... Biomedical micro-and nanodevices have potential uses that range from the analysis of ... Polymer and hydrogel-based microdevices have many attractive fea-tures for use in ... diagnostic devices for intelligent and integrated sensing with therapeutic mi-cro/nanoscale technologies ...

Journal of Physics: Condensed Matter, 2006

Journal of Physics: Condensed Matter, 2007

Monitoring of food and environmental samples for biological threats, such as Listeria monocytogen... more Monitoring of food and environmental samples for biological threats, such as Listeria monocytogenes, requires probes that specifically bind biological agents and ensure their immediate and efficient detection. There is a need for robust and inexpensive affinity probes as an alternative to antibodies. These probes may be recruited from random peptide libraries displayed on filamentous phage. In this study, we selected from two phage peptide libraries phage clones displaying peptides capable of specific and strong binding to the L. monocytogenes cell surface. The ability of isolated phage clones to interact specifically with L. monocytogenes was demonstrated using enzymelinked immunosorbent assay (ELISA) and confirmed by co-precipitation assay. We also assessed the sensitivity of phage-bacteria binding by PCR on phage-captured Listeria cells, which could be detected at a concentration of 10 4 cells ml −1 . In addition, as proof-of-concept, we tested the possibility of immobilizing the affinity-selected phages to a putative biosensor surface. The quality of phage deposition was monitored by ELISA and fluorescent microscopy. Phage-bacterial binding was confirmed by high power optical phase contrast microscopy. Overall, the results of this work validate the concept of affinity-selected recombinant filamentous phages as probes for detecting and monitoring bacterial agents under any conditions that warrant their recognition, including in food products.

International Journal of Biological Macromolecules, 2001

In this study, we investigated the ability of Pseudomonas aeruginosa ATCC 27853 to grow and synth... more In this study, we investigated the ability of Pseudomonas aeruginosa ATCC 27853 to grow and synthesize poly(3-hydroxyalkanoates) (PHAs) from saturated fatty acids with an even number of carbon atoms, from eight to 22, and from oleic acid. In a non-limiting medium, all carbon sources but docosanoic acid supported cell growth and PHA production, with eicosanoic acid giving the highest yield. In magnesium-limiting conditions, higher yields were obtained from sources with up to 16 carbon atoms. Composition was estimated by gas chromatography of methanolyzed samples and 13 C nuclear magnetic resonance. The 3-hydroxyalkanoate units extended from hexanoate to tetradecanoate or tetradecenoate, with octanoate and decanoate as the predominant components. Weight average molecular weights ranged from 78 000 to 316 000. Fast atom bombardment mass spectrometry of partially pyrolyzed samples, coupled to statistical analysis, showed that these PHAs are random copolymers.

The ability of Pseudomonas aeruginosa ATCC 27853 to grow and synthesize polyhydroxyalkanoates (PH... more The ability of Pseudomonas aeruginosa ATCC 27853 to grow and synthesize polyhydroxyalkanoates (PHAs) using Tween 20 as the sole carbon source was investigated. Tween 20 could support cell growth and PHA production. The polymer produced from Tween 20 was compared with those produced from its major free fatty acids components: lauric (C12), myristic (C14), and palmitic (C16) acids. Gas-chromatographic analysis

Foodborne Pathogens and Disease, 2011

Several foodborne human pathogens, when exposed to harsh conditions, enter viable but nonculturab... more Several foodborne human pathogens, when exposed to harsh conditions, enter viable but nonculturable (VBNC) state; however, still open is the question whether VBNC pathogens could be a risk for public health, because, potentially, they can resuscitate. Moreover, cultural methods for food safety control were not able to detect VBNC forms of foodborne bacteria. Particularly, it has not been established whether food chemophysical characteristics can induce VBNC state in contaminating pathogen bacterial populations, especially in food, such as salads and fresh fruit juices, not subjected to any decontamination treatment. In this preliminary study, we intentionally contaminated grapefruit juice to determine whether pathogen bacteria could enter VNBC state. In fact, grapefruit juice contains natural antimicrobial compounds, has an average pH of about 3 and low content in carbohydrates. Such characteristics make grapefruit juice a harsh environment for microbial survival. For this purpose, Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium ATCC 14028, Listeria monocytogenes ATCC 7644, and Shigella flexneri ATCC 12022, at two different inoculum sizes, have been used. Viability by the LIVE=DEAD BacLight Bacterial Viability kit and culturability by plate counts assay were monitored, whereas ''resuscitation'' of nonculturable populations was attempted by inoculation in nutrient-rich media. The data showed that L. monocytogenes lost both culturability and viability and did not resuscitate within 24 h independently on inoculum size, whereas E. coli O157:H7 was able to resuscitate after 24 h but did not after 48 h. Salmonella Typhimurium and S. flexneri, depending on inoculum size, lost culturability but maintained viability and were able to resuscitate; moreover, S. flexneri was still able to form colonies after 48 h at high inoculum size. In conclusion, entry into VBNC state differs on the species, depending, in turn, on inoculum size and time of incubation.

Biosensors and Bioelectronics, 2008

The design of novel biosensors for the detection of biological threats, such as Pseudomonas aerug... more The design of novel biosensors for the detection of biological threats, such as Pseudomonas aeruginosa, requires probes that specifically bind biological agents and insure their immediate and efficient recognition. Advanced bio-selective sensors may meet the requests for isolation, concentration of the agents and their real-time detection. There is a need for robust and inexpensive affinity probes alternative to antibodies. These probes may be recruited from random peptide libraries displayed on filamentous phage. In this study, we identified from two phage-displayed random peptide libraries phage clones displaying peptides capable of specific and strong binding to P. aeruginosa cell surface. The ability of the phage clones to interact specifically with P. aeruginosa was demonstrated by using enzyme-linked immunosorbent assay (ELISA). We assessed selectivity of phage-bacteria-binding by comparing the binding ability of the selected clones to the selector bacterium and a panel of other bacterial species; we also demonstrated by dot spot and immunoblotting that the most reactive and selective phage peptide bound with high avidity the bacterial cell surface. In addition, as proof-of-concept, we tested the possibility to immobilize the affinity-selected phage to a putative biosensor surface. The quality of phage deposition was monitored by ELISA, and phage-bacterial-binding was confirmed by high-power optical phase contrast microscopy. Overall, the results of this work validate the concept of affinity-selected recombinant filamentous phages as probes for detecting and monitoring bacterial agents under any conditions that warrant their recognition, including clinical-based diagnostics and possibly biological warfare applications.

Biomacromolecules, 2004

Pseudomonas aeruginosa ATCC 27853 accumulated poly(3-hydroxyalkanoates) (PHAs) after growth on sa... more Pseudomonas aeruginosa ATCC 27853 accumulated poly(3-hydroxyalkanoates) (PHAs) after growth on saturated fatty acids with an odd number of carbon atoms. No nutrient limitation was required to induce PHA synthesis, although better yields were obtained when the medium was magnesium deprived. A comparative study was carried out between PHAs obtained from C-odd and those from C-even carbon sources. Repeating units identification was performed by gas chromatography (GC) and capillary liquid chromatography-electrospray mass spectrometry (LC-ESI MS) of methanolyzed samples. When C-odd n-alkanoic acids from nonanoic to pentadecanoic were used the lowest hydroxyalkanoate unit found was 3-hydroxyvalerate and the highest 3-hydroxypentadecanoate, whereas when C-even acids from octanoic to eicosanoic were used these were 3-hydroxycaproate and 3-hydroxyeicosanoate, respectively. Weight average molecular weights were in the range 187 000-596 000. DSC traces showed Tm and DeltaHm which varied from 43 to 58 degrees C and from 5.9 to 24.8 J/g, with the PHAs generated from C-odd carbon sources having lower values. ESI MS of partially pyrolyzed samples allowed the identification of oligomers up to heptamers, and statistical analysis of the ions intensity in the mass spectra showed that these PHAs are random copolyesters.

2004 IEEE International Symposium on Circuits and Systems (IEEE Cat. No.04CH37512), 2004

Bacterial adhesion on surfaces is a very important complex phenomenon, since it is a determinant ... more Bacterial adhesion on surfaces is a very important complex phenomenon, since it is a determinant for the overall biofilm formation; the presence of biofilm can be both beneficial (i.e. to degrade hazardous substances in the soil or in a bioreactor) or detrimental (as on food, ship hulls and biomaterials implants or in the oral cavity). This work starts from a

Bacterial adhesion on surfaces is a very important complex phenomenon, since it is a determinant ... more Bacterial adhesion on surfaces is a very important complex phenomenon, since it is a determinant for the overall biofilm formation; the presence of biofilm can be both beneficial (i.e. to degrade hazardous substances in the soil or in a bioreactor) or detrimental (as on food, ship hulls and biomaterials implants or in the oral cavity). This work starts from a

Mathematical Biosciences and Engineering, 2008

In this work, aggregation states of bacteria on engineered surfaces are investigated both from th... more In this work, aggregation states of bacteria on engineered surfaces are investigated both from the experimental point of view and from the theoretical one. The starting point of this work is a series of experiments carried out on abiotic surfaces in which bacteria adhere forming self-organized patterns. To reproduce the main characteristics of the phenomenon a model based on self-organization of a group of agents has been used. The agents represent bacteria and are free to move on a given surface. On the basis of local rules they may adhere and then eventually form self-organized aggregates. Our numerical results demonstrate that few simple rules are able to explain the emergence of self-organized patterns. Depending on the parameters used, the model is able to reproduce the aggregation patterns observed under different experimental conditions and to predict the behavior of a culture of two bacterial species.

Langmuir, 2002

... Sperone, 31, Vill. S.Agata, 98166 Messina, Italy. Langmuir , 2002, 18 (24), pp 9469–9475. DOI... more ... Sperone, 31, Vill. S.Agata, 98166 Messina, Italy. Langmuir , 2002, 18 (24), pp 9469–9475. DOI: 10.1021/la025800x. Publication Date (Web): October 24, 2002. Copyright © 2002 American Chemical Society. Abstract. This paper reports ...

Surface and Interface Analysis, 2010

ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging has been shown to be a... more ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging has been shown to be a useful tool to study cell adhesion onto a surface. The purpose of this work was that of investigating by means of ToF-SIMS imaging the influence of different salt environments on the adhesion and self organization of Staphylococcus epidermidis ATCC 12228 onto a nonleaching surface (native silicon oxide). Chemical maps show that the different media influence the distribution of bacteria and that their different surface organization in different media is accompanied by characteristic distributions of alkali ions and organic fragments related to the bacteria. This could help in understanding the mechanisms involved in self organization of bacteria, that are thought to be related with the ability of bacteria to modify, by means of ionic fluxes through the cell membrane, the electrostatic interactions that, in turn, appear to rule their self organization in fractal patterns. Copyright © 2010 John Wiley & Sons, Ltd.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003

The paper reports evidence of the different cytocompatibility towards ion irradiated polymer surf... more The paper reports evidence of the different cytocompatibility towards ion irradiated polymer surfaces. In particular, we studied the cell attachment, adhesion and spreading of normal human dermal fibroblast cells onto poly(hydroxymethylsiloxane) and poly(ethyleneterephthalate) surfaces modified by 50 keV Ar þ beams. The cell response is discussed in connection with the radiation-induced changes of the polymers surface chemical structure and related surface free energy, investigated by means of X-ray photoelectron spectroscopy and static contact angle measurements.

Journal of Adhesion Science and Technology, 2011

Microbial adhesion and retention on surfaces are complex phenomena, critical to the formation and... more Microbial adhesion and retention on surfaces are complex phenomena, critical to the formation and development of biofilms. Recently, the focus of research has been more and more on the importance of retention of bacteria under fluctuating high shear forces in biofilm formation. The aim of the present work was to carry out a comparative study of the retention process of