Transcriptomic and proteomic analysis of Staphylococcus aureus response to cuminaldehyde stress.

The previous study indicated that cuminaldehyde (CUM) could be used as an antibacterial agent in sauced beef to reduce the propagation of Staphylococcus aureus (S. aureus). This research took sauced beef treated with 0.4 µL/mL CUM as the research object. Transcriptomic and proteomic methods were used to comprehensively analyze the changes in genes and proteins of S. aureus under CUM stress. A total of 258 differentially expressed genes (DEGs, 178 up-regulated and 80 down-regulated) and 384 differentially expressed proteins (DEPs, 61 up-regulated and 323 down-regulated) were found. It was observed that CUM destroyed the cell wall and cell membrane by inhibiting the synthesis of peptidoglycan and fatty acid. Low energy consumption strategies were formed by reducing glycolysis and ribosome de novo synthesis. The levels of genes and proteins associated with the glycine, serine, threonine, methionine, cysteine, and branched-chain amino acids were dramatically changed, which impaired protein synthesis and reduced bacterial viability. In addition, the up-regulated DEGs and DEFs involved in DNA replication, recombination and single-stranded DNA-binding contributed to DNA repair. Moreover, ATP-binding cassettes (ABC) transporters were also perturbed, such as the uptake of betaine and iron were inhibited. Thus, this study revealed the response mechanism of S. aureus under the stress of CUM, and provided a theoretical basis for the application of CUM in meat products.

Biocatalytical Acyl-Modification of Puerarin: Shape Gut Microbiota Profile and Improve Short Chain Fatty Acids Production in Rats.

Gut microbiota balance and metabolites have become a potentially mechanism in maintaining health. The specific aim of this study was to compare the modulation of puerarin and puerarin acid esters on gut microbial composition and metabolites. Male mice were fed a control diet or diets supplemented with puerarin, puerarin propanoate ester, puerarin hexanoate ester, puerarin myristate ester for 24 h, respectively. The result revealed that puerarin acid esters with different chain lengths showed different activities to create more own impacted bacterial. Puerarin propanoate and puerarin hexanoate ester significantly improved the diversity of microbiota and promoted the relative abundance of beneficial gut microbiota such as Lactobacillus, Barnesiella, Clostridium IV, Prevotella. Additionally, the puerarin propanoate ester group showed the capacity to deliver specific propionic acid to the colon. But esters with medium-long chain lengths had more opportunity to alter gut microbiota for enhancing the short chain fatty acids production. As a whole, puerarin acid esters with different chain lengths supplements shaped different gut microbial and short chain fatty acids metabolism, which could improve human health.

Evaluation of the digestion and transport profiles and potential immunocompetence of puerarin and its acylated derivatives.

Acylation has become one of the most widely used methods to improve the lipid solubility and bioavailability of flavonoids. In this study, puerarin acid esters (PAES) with different chain lengths were synthesized via biocatalytic acylation. This was the first study to evaluate the digestion and transport profiles and immunocompetence of PAES. The relationship between the digestion and transport profiles and potential immunocompetence of the acylated derivatives in Caco-2 cell monolayers was also explored. Puerarin and PAES remained stable in gastric phases, whereas different degrees of hydrolysis of PAES were found in the intestine. PAES with less than 12 carbon chains were positively correlated with the degree of hydrolysis, while those with more than 12 carbon chains showed higher resistance to hydrolysis by the artificial human digestive juice. The apparent permeability coefficients of puerarin, puerarin acetate, puerarin propanoate, puerarin butyrate, puerarin hexanoate, puerarin octanate and puerarin laurate were 1.62 ± 0.09, 1.70 ± 0.15, 1.89 ± 0.19, 1.86 ± 0.18, 2.29 ± 0.12, 4.06 ± 1.01 and 2.32 ± 0.88 × 10-6 cm s-1, respectively, in Caco-2 cell monolayers. The results of the immune factor assays indicated that puerarin propanoate, puerarin hexanoate and puerarin myristate could significantly promote the secretion of IL-6, TNF-α and IL-10. These findings suggested that a better absorption could be predicted after oral intake using PAES. Meanwhile, the concentration of esters and their metabolites (puerarin) found in the digestion and transport profiles directly affected their potential immunocompetence.

Bioavailability of quercetin in zein-based colloidal particles-stabilized Pickering emulsions investigated by the in vitro digestion coupled with Caco-2 cell monolayer model.

Protein-based Pickering emulsions have received considerable attention as nutraceutical vehicles. However, the oral bioavailability of nutraceuticals encapsulated in Pickering emulsions was not well established. In this work, a simulated gastrointestinal tract/Caco-2 cell culture model was applied to investigate the oral bioavailability of quercetin encapsulated in zein-based Pickering emulsions with quercetin in zein particles as the control. Pickering emulsions with shell (ZCP-QE) and core quercetin (ZCPE-Q) were constructed, and quercetin bioaccessibility, cell uptake and secretion, and the overall bioavailability were evaluated and compared. The overall oral bioavailability of quercetin was increased from 2.71% (bulk oil) to 38.18% (ZCPs-Q) and 18.97% (ZCPE-Q), particularly reached 41.22% for ZCP-QE. This work took new insights into the contributions of bioaccessibility and absorption (cell uptake plus secretion) to the overall oral bioavailability of quercetin. A schematic representation is proposed to relate the types of colloidal nanostructures in the digesta to the uptake, cell absorption, and overall oral bioavailability of quercetin. This study provided an attractive basis for identifying effective strategies to improve the oral bioavailability of hydrophobic nutraceuticals.

Hofmeister Effect-Assistant Fabrication of All-Natural Protein-based Porous Materials Templated from Pickering Emulsions.

Porous materials derived from natural and biodegradable polymers have received growing interest. We demonstrate here an attractive method for the preparation of protein-based porous materials using emulsions stabilized by gliadin-chitosan hybrid particles (GCHPs) as the template, with the addition of gelatin and kosmotropic ions to improve the mechanical strength. The microstructure, mechanical properties, cytotoxicity, and fluid absorption behavior of porous materials were systematically investigated. This strategy facilitated the formation of porous materials with highly open and interconnected pore structure, which can be manipulated by altering the mass ratio of hexane or gelatin in the matrix. The Hofmeister effect resulted from kosmotropic ions greatly enhanced the Young's modulus and the compressive stress at 40% strain of porous materials from 0.56 to 6.84 MPa and 0.26 to 1.11 MPa, respectively. The developed all-natural porous materials were nontoxic to HaCaT cells; they also had excellent liquid (i.e., simulated body fluid and rabbit blood) absorption performance and advantages in resisting stress and maintaining geometry shape. The effects of different concentration amounts and type of salts in the Hofmeister series on the formation and performance of porous materials were also explored. Mechanical strength of porous materials was gradually enhanced when the (NH4)2SO4 concentration increased from 0 to 35 wt %, and the other four kosmotropic salts, including Na2S2O3, Na2CO3, NaH2PO4, and Na2SO4, also showed positive effects. This work opens a simple and feasible way to produce nontoxic and biodegradable porous materials with favorable mechanical strength and controllable pore structure. These materials have broad potential application in many fields involving biomedical and material science, such as cell culture, (bio)catalysis, and wound or bone defect healing.

Cellular Uptake and Intracellular Antioxidant Activity of Zein/Chitosan Nanoparticles Incorporated with Quercetin.

In this work, zein/chitosan nanoparticles (ZCPs-Q) were developed for encapsulating quercetin to overcome its lower water solubility and instability, and to concomitantly enhance its cellular uptake and intracellular antioxidant activity. This strategy enhanced quercetin solubility 753.6 and 9.95 times in water and PBS (7.4), respectively, and quercetin encapsulated in ZCPs remained stable after UV irradiation and heat treatment. ZCPs-Q could significantly attenuate AAPH induced erythrocyte hemolysis through the inhibition of ROS generation. It restored intracellular antioxidant enzyme (SOD and GSH-Px) activities to normal levels and inhibited intracellular malondialdehyde (MDA) formation. Simultaneously, ZCPs-Q showed a strong antioxidant activity in HepG2 cells with an EC50 value of 31.18 µg/mL, which was lower than free quercetin's 41.02 µg/mL. ZCPs enhanced the uptake efficiency of quercetin in Caco-2 cells, which contributed to the improvement of cellular antioxidant activities (CAA) evaluated with the CAA assay and AAPH-induced erythrocyte hemolysis assay. The designed route is particularly suitable for the encapsulation of water-insoluble nutraceuticals and for enhancing cell uptake and CAA.

Molecular characterization of Lactobacillus plantarum DMDL 9010, a strain with efficient nitrite degradation capacity.

Nitrites commonly found in food, especially in fermented vegetables, are potential carcinogens. Therefore, limiting nitrites in food is critically important for food safety. A Lactobacillus strain (Lactobacillus sp. DMDL 9010) was previously isolated from fermented vegetables by our group, and is not yet fully characterized. A number of phenotypical and genotypical approaches were employed to characterize Lactobacillus sp. DMDL 9010. Its nitrite degradation capacity was compared with four other Lactobacillus strains, including Lactobacillus casei subsp. rhamnosus 719, Lactobacillus delbrueckii subsp. bulgaricu 1.83, Streptococcus thermophilus 1.204, and lactobacillus plantarum 8140, on MRS medium. Compared to these four Lactobacillus strains, Lactobacillus sp. DMDL 9010 had a significantly higher nitrite degradation capacity (P<0.001). Based on 16S rDNA sequencing and sequence comparison, Lactobacillus sp. DMDL 9010 was identified as either Lactobacillus plantarum or Lactobacillus pentosus. To further identify this strain, the flanking regions (922 bp and 806 bp upstream and downstream, respectively) of the L-lactate dehydrogenase 1 (L-ldh1) gene were amplified and sequenced. Lactobacillus sp. DMDL 9010 had 98.92 and 76.98% sequence identity in the upstream region with L. plantarum WCFS1 and L. pentosus IG1, respectively, suggesting that Lactobacillu sp. DMDL 9010 is an L. plantarum strain. It was therefore named L. plantarum DMDL 9010. Our study provides a platform for genetic engineering of L. plantarum DMDL 9010, in order to further improve its nitrite degradation capacity.

Safety and efficacy of frameless stereotactic brain biopsy techniques.

OBJECTIVE: To explore the safety and efficacy of frameless stereotactic brain biopsy. METHODS: Diagnostic accuracy was calculated by comparing biopsy diagnosis with definitive pathology in 62 patients who underwent frameless stereotactic brain biopsy between January 2008 and December 2010 in Xiamen University Southeast Hospital. Preoperative characteristics and histological diagnosis were reviewed and then information was analysed to identify factors associated with the biopsy not yielding a diagnosis and complications. RESULTS: Diagnostic yield was 93.5%. No differences were found between pathological diagnosis and frozen pathological diagnosis. The most common lesions were astrocytic lesions, included 16 cases of low-grade glioma and 12 cases of malignant glioma. Remote hemorrhage, metastasis, and lymphoma were following in incidence. Multiple brain lesions were found in 17 cases (27.4%). Eleven cases were frontal lesions (17.7%), 8 were frontotemporal (12.9%), 6 were frontoparietal (9.7%), and 5 each were temporal, parietal, and parietotemporal lesions (8.1%). Postoperative complications occurred in 21.0% of the patients after biopsies, including 10 haemorrhages (16.1%) and 3 temporary neurological deficits (1 epilepsy, 1 headache, and 1 partial hemiparesis). No patient required operation for hematoma evacuation. CONCLUSION: Frameless stereotactic biopsy is an effective and safe technique for histologic diagnosis of brain lesions, particularly for multifocal and frontal lesions.

Detection of viable but nonculturable Escherichia coli O157:H7 using propidium monoazide treatments and qPCR.

Escherichia coli O157:H7 can enter into a viable but nonculturable (VBNC) state under stress conditions. The aims of the present study were to examine the influences of environmental factors on the survivability and culturability of E. coli O157:H7 and to develop an approach for accurate detection of VBNC E. coli O157:H7. The E. coli O157:H7 strain ATCC 6589 was inoculated into 3 induction microcosm models: (i) Luria-Bertani broth, (ii) sterilized tap water, and (iii) sterilized physiological saline solution. Our results showed that low temperature and nutritional starvation significantly impacted on the survivability of E. coli O157:H7 cells and that the in-vitro-induced VBNC cells were capable of resuscitating under normal temperature and appropriate nutrients. We tested the effectiveness of an approach combining propidium monoazide (PMA) treatment with real-time polymerase chain reaction (PMA-qPCR) for accurate quantification of total, viable, dead, and VBNC cells under different induction microcosm models. Our results indicated different threshold cycle (Ct) values for PMA-treated cells and untreated cells (ΔCt = 4.97, 4.29, and 3.30 for Luria-Bertani broth, sterilized tap water, and sterilized physiological saline solution, respectively). We determined the quantification limit of this PMA-qPCR approach to be 1 × 10(2) cells·mL(-1), providing sufficient sensitivity for detection of VBNC E. coli O157:H7 cells to no less than 100 cells·mL(-1). This study clearly demonstrated the feasibility and effectiveness of using PMA-qPCR to accurately quantify E. coli O157:H7 in a VBNC state.

A facile whole-cell biocatalytic approach to regioselective synthesis of monoacylated 1-ß-D-arabinofuranosylcytosine: influence of organic solvents.

The lyophilized Pseudomonas fluorescens cell was an efficient alternative catalyst to enzymes for highly regioselective acylation of a polar nucleoside, 1-ß-D-arabinofuranosylcytosine (ara-C). The cells showed an evident solvent dependence in the reaction. Among the tested solvents except for acetonitrile-pyridine, catalytic activity of the cells clearly increased with increasing the polarity of the organic solvents used. Among all the tested solvents both pure and binary, the best results were observed in isopropyl ether-pyridine system, in which the catalyst also showed good thermal and operational stabilities. For the biocataylsis in isopropyl ether-pyridine, the optimal isopropyl ether concentration, water content, acyl donor/ara-C ratio, biocatalyst dosage and reaction temperature were 30% (v/v), 4%, 45, 50mg/mL and 30 °C, respectively, under which the initial rate, yield and 5'-regioselectivity were 2.93 mM/h, 77.1% and 97.3%, respectively. The bacterial cells exhibited comparable 5'-regioselectivity to the expensive immobilized enzyme, which could also have environmental and cost advantages.

A novel biocatalytic approach to acetylation of 1-ß-D-arabinofuranosylcytosine by Aspergillus oryzae whole cell in organic solvents.

Biocatalytic acylation of 1-ß-D-arabinofuranosylcytosine (ara-C) was developed using whole cell of Aspergillus oryzae as a novel catalyst. (13)C nuclear magnetic resonance (NMR) analysis indicated that the whole-cell biocatalyst had more specific activity toward the 3'-hydroxyl group than 5'-hydroxyl group among the available hydroxyl groups in sugar moiety of ara-C. Except for glucose and maltose, 11 carbon sources supplemented to basal media, including Spans, Tweens, olive oil and oleic acid, exhibited notable enhancement effects on both the cell growth and the acylation reactions. It was suggested that the carbon sources containing controlled-release oleic acid were the important substrates for the production of fungal cell-bound lipase with specific activity, partially due to a gradual induction effect of their released oleic acid on the cell-bound lipase production. Despite the low initial reaction rate and substrate conversion, the addition of 2.0 g/l Span 80 resulted in a higher 3'-regioselectivity of the cells than 81%. By using Tween 85 at its optimum concentration of 5.0 g/l, however, the highest initial rates (3.2 mmol/l h) and substrate conversion (76%) of the whole-cell catalyzed acylation of ara-C can be achieved. It was also found that the 3'-regioselectivity of the cells showed observable increase by extending the culture time. And the activity of cell-bound lipase drastically increased in the early stage of cell growth and then declined in the late culture stage, whatever the culture media used. Our results thus indicated that A. oryzae whole cell was a promising green tool for biosynthesis of nucleoside esters with potential bioactivities.

In vitro antioxidant activity of Bombax malabaricum flower extracts.

CONTEXT: Bombax malabaricum DC. (Bombacaceae) is a traditional Chinese herbal medicine used for the treatment of inflammatory conditions, diarrhea, fever, chronic inflammation, catarrhal affection, and as a diuretic. However, little information is available about its antioxidative activity. OBJECTIVE: Water, 50% ethanol, and 80% acetone extracts from flowers of B. malabaricum were investigated for their in vitro antioxidant activity in this article for the first time. Then the relationships between antioxidant activity measured by different methods and total phenolic content (TPC) and total flavonoid content (TFC) were established. MATERIALS AND METHODS: The antioxidant activities of extracts from B. malabaricum flower were investigated including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, oxygen radical absorbance capacity (ORAC), reducing power, and inhibition on phosphatidylcholine liposome peroxidation. RESULTS: Results showed that all the extracts possessed remarkable antioxidant capacity compared with ascorbic or gallic acids. Total antioxidant activities evaluated by ORAC assay of different extracts ranged from 700.03 to 1482.46 µmol Trolox equivalents/g. The highest TPC of 130.38 mg gallic acid equivalents (GAE)/g was observed in 80% acetone extract, whereas the lowest TPC of 57.09 mg GAE/g was obtained in the water extract. Furthermore, TFC exhibited significant (P < 0.05) positive correlations with DPPH radical-scavenging activity, ORAC, and reducing power. DISCUSSION AND CONCLUSION: These findings demonstrate that the flowers of B. malabaricum have excellent antioxidant activities and thus might be a potential source of natural antioxidants.

A multipathogen selective enrichment broth for simultaneous growth of Salmonella enterica serovar Enteritidis, Staphylococcus aureus, and Listeria monocytogenes.

A selective enrichment broth (SSL) was formulated to allow concurrent growth of 3 prominent food-borne pathogens: Salmonella enterica serovar Enteritidis, Staphylococcus aureus, and Listeria monocytogenes. Nalidixic acid, lithium chloride, and potassium tellurite were added as the selective agents, while sodium pyruvate and mannitol were employed as the supplemented elements. In the individual growth trial, the target pathogens were capable of growing in SSL to as high as 7-8 log(10) colony-forming units (CFU)/mL after 24 h incubation at 37 degrees C when being inoculated at 50-100 CFU/mL. In the simultaneous growth trial, the 3 combined target pathogens showed similar growth rates. The results show that SSL could support the successful simultaneous enrichment of 3 pathogens; however, SSL inhibited the growth of nontarget bacteria. In the artificial contaminated raw beef and ready-to-eat chicken, a high recovery of these 3 target pathogens was obtained in SSL. Finally, Salmonella Enteritidis, Staphylococcus aureus, and L. monocytogenes were detected from 710 suspicious food samples by SSL with real-time PCR, and no false-positive or -negative results were reported. In summary, SSL has been shown to be a suitable broth for the simultaneous detection of the 3 prominent food-borne pathogens by multipathogen detection on a single-assay platform.

A multipathogen selective enrichment broth for simultaneous growth of Salmonella spp., Vibrio parahaemolyticus, and Vibrio cholerae.

A selective enrichment broth (SVV) was formulated to allow concurrent growth of Salmonella spp., V. parahaemolyticus, and V. cholerae. Potassium tellurite and sodium citrate were added as the inhibitors, while glucose, mannitol, anhydrous sodium sulfite and sodium pyruvate were employed as the growth-promoters. When mixed in equal or varied proportions, the target pathogens in SVV had a great accumulation (10(5)-10(8) CFU/ml) and effectively inhibited the growth of competitive microflora. In the artificially contaminated samples, a high recovery of these 3 target pathogens was obtained in SVV. Finally, Salmonella spp., V. parahaemolyticus, and V. cholerae were detected from 608 suspicious food samples by SVV with real-time PCR, and no false-positive or -negative results were reported. In summary, SVV has been shown to be a suitable broth for the simultaneous detection of the 3 pathogens by multipathogen detection on a single-assay platform.

Simultaneous detection of enterovirus 70 and coxsackievirus A24 variant by multiplex real-time RT-PCR using an internal control.

Epidemics of acute hemorrhagic conjunctivitis are always explosive and extensive, and have been recognized as a serious international public health problem. Enterovirus 70 and coxsackievirus A24 variant have been identified as the major etiological agents in acute hemorrhagic conjunctivitis outbreaks worldwide. A novel multiplex real-time RT-PCR assay was developed for simultaneous detection, identification and quantitation of enterovirus 70 and coxsackievirus A24 variant. The specificity, sensitivity and reproducibility of the method were analyzed and 125 clinical samples were tested using this method. No cross-reactivity with other enteroviruses strains was detected. The detection limits achieved were 10 copies/tube of enterovirus 70 and 100 copies/tube of coxsackievirus A24 variant respectively, and the addition of the internal control does not compromise the sensitivity or specificity. One hundred and twenty five clinical samples were tested and the results were consistent with the results obtained by using virus isolation followed by neutralization and sequencing of VP1 region. Due to its high specificity, sensitivity and elimination of false negative results by the internal control, this assay is suitable for both research applications and rapid clinical diagnosis of enterovirus 70 and coxsackievirus A24 variant.

Simultaneous detection of human enterovirus 71 and coxsackievirus A16 in clinical specimens by multiplex real-time PCR with an internal amplification control.

The recent and continuing HFMD outbreak caused by EV71 in several provinces of China since March 2008 has affected thousands of children and resulted in nearly 50 deaths. In this study, a sensitive and specific multiplex real-time RT-PCR assay has been developed for the rapid detection of EV71 and CV-A16. By using an internal amplification control, the real-time assay achieves detection of samples containing inhibitors and avoids false negatives. It should prove useful for clinical diagnosis of EV71 or CV-A16 infections.

Rapid detection of a highly virulent Chinese-type isolate of Porcine Reproductive and Respiratory Syndrome Virus by real-time reverse transcriptase PCR.

An outbreak of highly virulent Chinese-type of Porcine Reproductive and Respiratory Syndrome Virus (H-PRRSV) in most areas of China recently has led to huge economic losses and drawn great attention to its diagnosis and disease control. To facilitate rapid identification of H-PRRSV, a fluorogenic-probe hydrolysis (TaqMan)-reverse transcriptase PCR for H-PRRSV has been developed. Primers and probe specificity were evaluated with RNA extracted from 5 strains of H-PRRSV and 24 strains of other viruses, the results showed 100% specificity for the selected panel. The assay met the sensitivity of 1 50% tissue culture infective dose (TCID50) per ml of samples from infected pigs. Analysis with 10(5)-1TCID50/ml H-PRRSV samples demonstrated high reproducibility with a coefficient of variation (CV) of 0.5-2.5%. More than two hundred samples from lung, spleen, blood serum specimens obtained from 22 outbreaks of suspected H-PRRS from March to June in 2007 were verified using this assay. The results showed that 68.5% (146 out of 213) of these samples were positive which is 100% consistent with that of the sequencing method. The assay can be performed in less than 3h and thus provide a rapid method for the diagnosis of H-PRRSV as well as for elucidation of the epidemiology of H-PRRSV infections.

The study of 3-dimensional structures of IgG with atomic force microscopy.

OBJECTIVE: To detect 3-dimensional images of anti-N-methyl-D-aspartate receptor Nr1 (NMDAr1) polycolonal IgG affixed on mica in physiological environment. METHODS: The images and data were obtained from a contact mode and commercial Si3N4 probed tip by using atomic force microscope (AFM). RESULTS: The anti-NMDAr1 polycolonal IgG has a characteristic structure described as an ellipse spherical shape of 136.4 A x 62.8 A x 26.1 A. On the section of the ellipse edge there were two peaks about 13 nm in width. CONCLUSIONS: Using AFM to investigate biomacromolecule can make us deeply understand the structure of IgG, which will instruct us to detect the membrane receptor protein as a labelling agent.

[Dynamic atomic force microscopic observation of the three-dimensional conformation of protein A-gold single molecule].

OBJECTIVE: To determine the three-dimensional (3D) conformation of staphylococcal protein A-gold (SPA-G) single molecule using atomic force microscope (AFM) so as to evaluate the feasibility of using this molecule for in situ labeling of the neuronal membrane protein. METHODS: AFM was used to acquire the images of SPA-G binding to the surface of mica under physiological condition for determining the 3D conformation of the molecule. RESULTS: SPA-G single molecule was shown to contain a characteristic structure with a chain in the shape of mirror image of the letter C, which had the dimension of 48.80 nm x 42.13 nm x 20.53 nm. CONCLUSION: AFM provide a new means for morphological investigation of the biomacromolecule at the nanometer scale in physiological conditions, and SPA-G can be utilized for in situ labeling of the neuronal membrane receptors.

[Application of atomic force microscope in life science research].

OBJECTIVE: Atomic force microscope (AFM) is one of the most recent imaging and manipulation techniques in biological science. Among its various merits, AFM typically enables simple sample preparation, acquisition of three-dimensional images to identify single atoms under different conditions, detection of the interactive forces between two single biomolecules and their manipulation. AFM is currently applied in the research of the structure and function, at the nanometric scale, of various tissues, cells, microbes and biomolecules, and studies of the interaction between two biomolecules as well as the manipulation of some biological processes. AFM possesses the potential to become an important instrument in life science research, in spite of its current limits that require improvements such as in carbon nanotube tip, rigidity of soft biological samples and result interpretation.