Measurement of the flexibility of wet cellulose fibres using atomic force microscopy

Flexibility and modulus of elasticity data for two types of wet cellulose fibres using a direct force–displacement method by means of AFM are reported for never dried wet fibres immersed in water. The flexibilities for the bleached softwood kraft pulp (BSW) fibres are in the range of 4–38 × 10¹² N^?1 m^?2 while the flexibilities for the thermomechanical pulp (TMP) fibres are about one order of magnitude lower. For BSW the modulus of elasticity ranges from 1 to 12 MPa and for TMP between 15–190 MPa. These data are lower than most other available pulp fibre data and comparable to a soft rubber band. Reasons for the difference can be that our measurements with a direct method were performed using never dried fibres immersed in water while other groups have employed indirect methods using pulp with different treatments.     

Qualitative evaluation of microfibrillated cellulose using the crill method and some aspects of microscopy

It has been a challenge to develop rapid online characterisation techniques for nanocellulose given the fibrillar structure of the nanoparticles. The crill optical analyser uses optical response signals in the infrared (IR) and ultraviolet (UV) wavelength ranges to evaluate the particle size properties of micro/nanofibrillar cellulosic materials. In this work, the crill analyser was used to measure the projected areas of UV and IR light sources by measuring the light blocked by nanocellulosic particles. This work uses the crill methodology as a new, simplified technique to characterise the particle size distribution of nanocellulosic material based on chemi-thermomechanical pulp (CTMP), thermomechanical pulp (TMP), and sulphite pulp (SP). In the first part, hydrogen peroxide pretreatment of CTMP and TMP in a wing mill refiner followed by high-pressure homogenisation to produce microfibrillated cellulose (MFC) was evaluated using the crill method. In the second part, TEMPO oxidation of CTMP and SP combined with high-shear homogenisation to produce MFC was studied using the crill method. With 4 % hydrogen peroxide pretreatment, the crill values of the unhomogenised samples were 218 and 214 for the TMP and CTMP, respectively, improving to 234 and 229 after 18 homogenisation passes. The results of the TEMPO method indicated that, for the 5 mmol NaClO SP-MFC, the crill value was 108 units at 0 min and 355 units after 90 min of treatment, a 228 % improvement. The CTMP and TMP fibres and the MFC were freeze dried and fibrillar structure of the fibres and microfibrils was visualised using scanning electron and transmission electron microscopy.     

Novel multifunctional water- and oil-repellent,antibacterial, and flame-retardant cellulose fibres created by the sol–gel process

This research aimed to prepare cotton fibres with novel multifunctional water- and oil-repellent, antibacterial, and flame-retardant properties. A three-component equimolar sol mixture, which included 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride, and P,P-diphenyl-N-(3-(trimethoxysilyl)propyl) phosphinic amide, was applied to the cotton fabric using the sol–gel process. The presence of the coating on the cotton fibres was confirmed by Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy. The functional properties of the coated cotton fabric were determined from liquid contact angle measurements and antibacterial activity, burning behaviour, and thermo-oxidative stability studies. The results demonstrate that a unique, compatible, and uniform organic-inorganic hybrid polymer network was formed on the fabric surface, which preserved its simultaneous hydrophobic (water contact angle of 135 ± 2°), oleophobic (n-hexadecane contact angle of 117 ± 1°), and bactericidal (bacterial reduction of 100 %) properties and incorporated the enhanced thermo-oxidative stability of the modified cellulose fibres.     

Superhydrophobic foam-like cellulose made of hydrophobized cellulose fibres

Wood (kraft) pulp was first dried into a low-density foam-like material by solvent-exchange with anhydrous ethanol. X-Ray tomography showed that, while pulp fibres are flat and resemble ribbons when dried from water, those dried from ethanol are quasi-tubular, inferring that capillary forces derived from a low surface tension solvent are not strong enough to promote fibre lumen collapse, contrary to what happens in water. When the resulting foam-like pulp was then subjected to a vapour phase reaction with trichloromethylsilane (TCMS) a silicon based polymeric coating was created on the surface of the fibres, and the totality of the hydroxyl groups (–OH) on the external surface of cellulose fibres and the internal surface of micropores in the fibre wall became silylated, whereas the surface of the nanopores was inaccessible to TCMS. The novelty lies in the ability to modify both the external surface and the internal micropore structure of cellulose fibres from 50 to 100 % silane coverage, which results in a novel superhydrophobic material, with a contact angle of approximately 150°. This is the first time cellulose is hydrophobized both internally and externally. We refer to the resulting foam as Cellufoam.     

Isolation and characterization of cellulose nanoplatelets from the parenchyma cells of <Emphasis Type="Italic">Agave salmiana</Emphasis>

We present a novel nanostructure in the form of cellulose nanoplatelets (CNPs) with an inner array of entangled nanofibrils. The planar structure was isolated from the parenchyma cells of Agave salmiana first using basic pretreatment, then by dissolving lignin and hemicellulose using acid hydrolysis, and finally by modifying the cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). The crystallinity index was calculated following the purification process, and it was found that nanocellulose was 30% more crystalline than the raw material. Using transmission electron microscopy, it was found that the nanoplatelets comprise ~2–3 nm long cellulose entangled nanofibrils. In addition, via atomic force microscopy, the morphology of the nanoplatelets was confirmed; they were 90 nm thick for the acid hydrolyzed sample and 70 nm thick for the TEMPO-modified sample; their lateral size varied from a few to hundreds of micrometers, presenting large aspect ratios. Finally, CNPs were isolated and processed into thin paper with a thickness of 100 µm and transmittance of 86%, demonstrating great potential as a transparent film.     

SEC-MALLS analysis of TEMPO-oxidized celluloses using methylation of carboxyl groups

Two cellouronic acids [sodium (1 → 4)-β-polyglucuronates, CUAs] and one 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized wood cellulose (TOC) became soluble in 8 % lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) after the methylation of C6 carboxyl groups in these samples using trimethylsilyldiazomethane (TMSD). The obtained solutions were diluted to 1 % LiCl/DMAc and subjected to size-exclusion chromatography combined with multi-angle laser-light scattering (SEC-MALLS). Neither depolymerization nor side reactions took place during methylation; this was confirmed by SEC-MALLS and nuclear magnetic resonance analyses, using CUAs as models. The SEC-MALLS analysis of the original wood cellulose and the carboxyl-methylated TOC prepared from it, using 1 % LiCl/N,N-dimethyl-2-imidazolidinone and 1 % LiCl/DMAc, respectively, as eluents, showed that the weight-average degree of polymerization of the original wood cellulose decreased from 3,100 to 2,210 through TEMPO-mediated oxidation. The molecular-mass distributions of the original wood cellulose and the TOC both consisted of one large peak with a small shoulder, indicating that some of the oxidized hemicelluloses remained in the TOC. The combination of methylation of carboxyl groups in polysaccharides using TMSD and subsequent SEC-MALLS analysis using 1 % LiCl/DMAc as an eluent may be applicable not only to TOCs, but also to other polysaccharides with carboxyl groups, for evaluation of their molecular-mass parameters.     

Effects of mechanical stretching on average orientation of cellulose and pectin in onion epidermis cell wall: A polarized FT-IR study

The organization of polysaccharides in plant cell walls is important for the mechanics of plant cells. Spectral analysis of cell walls by polarized IR can reveal polysaccharide organization, but may be complicated by dipoles not aligned with the backbone. For instance, analysis of uniaxially-aligned cellulose Iβ film revealed that the dipole transition vector of the 1160 cm^?1 band involving stretch vibrations of glycosidic C1–O–C4 linkages is approximately at 30° with respect to the backbone of the cellulose chain, because of coupling with C5–O–C1 bonds in the six-membered rings. In the case of homogalacturonan, the dipole transition vector of the ester carbonyl group vibration (ν_C=O, 1745 cm^?1) is expected to be nearly normal to the homogalacturonan backbone. Using this information and the dichroism equation, the change in net orientation of cell wall polymers upon mechanical stretch was determined by polarized IR analysis. Never-dried abaxial outer epidermal cell walls of the second scale of onion bulb were mechanically stretched along longitudinal or transverse directions with respect to the long axis of the cells and then dried while under mechanical stretch. The average orientations of both 1160 and 1745 cm^?1 vibration transition dipoles were rotated by ~5° and ~4°, respectively, along the stretch direction from their initial random distributions upon longitudinal strain by 14%; and by ~4° and ~3°, respectively, upon transverse strain by 12%. These results imply that both cellulose microfibrils and pectins in the cell wall are passively realigned along the stretch direction by external mechanical force. The analytical methodology developed here will be useful to study how cell wall polymers might reorganize during cell wall growth and development.     

Bound water restrained by nanocellulose fibres

The higher-order structure of natural cellulose fibres changes in the presence of water. In order to investigate the effect of molecular level fibre structure, melting behaviour of water restrained by nano- and microcellulose fibre was measured by differential scanning calorimetry. Fibre size was measured by scanning electron microscopy and atomic force microscopy. It was found that the melting peak of water restrained by microcellulose fibre started at 250–260 K in a W _c (=mass of water/mass of dry sample) range from 0.5 to 1.2, whereas that of nanocellulose fibre was 230–237 K. Furthermore, peak temperature of melting of water restrained by nanocellulose was observed at around 270 K, in contrast, that of water restrained by microcellulose fibre was observed at ca. 275 K. Bound water content was calculated from melting enthalpy. Both non-freezing and freezing bound water of nanocellulose fibre was far larger than that of microcellulose. The above results suggest that a large amount of freezing bound water is restrained in nanocellulose fibres. It is thought that a larger number of isolated hydroxyl groups exist on the fibre surface.     

Crystallization of cellulose microfibrils in wood cell wall by repeated dry-and-wet treatment, using X-ray diffraction technique

The purpose of this study is to investigate the effect of repeated moisture change on the crystallinity and crystal size of cellulose microfibrils (CMF) in sugi (Cryptomeria japonica D.Don) and karamatsu (Larix kaempferi Gord.) wood cell wall. Based on obtained results, we discussed the qualitative change in the fine structure of CMF caused by repeated dry-and-wet (RDW) treatments. Green quarter-sawn specimens (5 × 16 × 15 mm in thickness × length × width) and microcrystalline cellulose powder (Avicel) were prepared, and these specimens were subjected to 7 times at most of heated or unheated RDW treatments. After giving RDW treatments, specimens were seasoned to the fiber saturated point and absolutely dried. Wide angle X-ray diffraction measurements were adopted to determine the crystallinity and the crystal size in each condition. Results indicate that crystallinity and crystal size in wood specimens gradually increased with the progress of heated or unheated RDW treatments, while no such increases were observed in Avicel powder. Those results suggest that RDW treatments promote the crystallization of CMF in wood cell wall, regardless of heating. We presume that noncrystalline cellulose forms hydrogen bonding with the cellulose at the surface of crystalline region with the progress of RDW treatments, thus enlarging the crystal size. Avicel powder did not show features that were observed in wood specimens by RDW treatments, because it contained few noncrystalline cellulose.     

Cellulose I crystallinity determination using FT–Raman spectroscopy: univariate and multivariate methods

Two new methods based on FT–Raman spectroscopy, one simple, based on band intensity ratio, and the other using a partial least squares (PLS) regression model, are proposed to determine cellulose I crystallinity. In the simple method, crystallinity in cellulose I samples was determined based on univariate regression that was first developed using the Raman band intensity ratio of the 380 and 1,096 cm^?1 bands. For calibration purposes, 80.5% crystalline and 120-min milled (0% crystalline) Whatman CC31 and six cellulose mixtures produced with crystallinities in the range 10.9–64% were used. When intensity ratios were plotted against crystallinities of the calibration set samples, the plot showed a linear correlation (coefficient of determination R ² = 0.992). Average standard error calculated from replicate Raman acquisitions indicated that the cellulose Raman crystallinity model was reliable. Crystallinities of the cellulose mixtures samples were also calculated from X-ray diffractograms using the amorphous contribution subtraction (Segal) method and it was found that the Raman model was better. Additionally, using both Raman and X-ray techniques, sample crystallinities were determined from partially crystalline cellulose samples that were generated by grinding Whatman CC31 in a vibratory mill. The two techniques showed significant differences. In the second approach, successful Raman PLS regression models for crystallinity, covering the 0–80.5% range, were generated from the ten calibration set Raman spectra. Both univariate-Raman and WAXS determined crystallinities were used as references. The calibration models had strong relationships between determined and predicted crystallinity values (R ² = 0.998 and 0.984, for univariate-Raman and WAXS referenced models, respectively). Compared to WAXS, univariate-Raman referenced model was found to be better (root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) values of 6.1 and 7.9% vs. 1.8 and 3.3%, respectively). It was concluded that either of the two Raman methods could be used for cellulose I crystallinity determination in cellulose samples.     

Nanofibrillated cellulose/nanographite composite films

Though research into nanofibrillated cellulose (NFC) has recently increased, few studies have considered co-utilising NFC and nanographite (NG) in composite films, and, it has, however been a challenge to use high-yield pulp fibres (mechanical pulps) to produce this nanofibrillar material. It is worth noting that there is a significant difference between chemical pulp fibres and high-yield pulp fibres, as the former is composed mainly of cellulose and has a yield of approximately 50 % while the latter is consist of cellulose, hemicellulose and lignin, and has a yield of approximately 90 %. NFC was produced by combining TEMPO (2,2,6,6-tetramethypiperidine-1-oxyl)-mediated oxidation with the mechanical shearing of chemi-thermomechanical pulp (CTMP) and sulphite pulp (SP); the NG was produced by mechanically exfoliating graphite. The different NaClO dosages in the TEMPO system differently oxidised the fibres, altering their fibrillation efficiency. NFC–NG films were produced by casting in a Petri dish. We examine the effect of NG on the sheet-resistance and mechanical properties of NFC films. Addition of 10 wt% NG to 90 wt% NFC of sample CC2 (5 mmol NaClO CTMP-NFC homogenised for 60 min) improved the sheet resistance, i.e. from that of an insulating pure NFC film to 180 Ω/sq. Further addition of 20 (CC3) and 25 wt% (CC4) of NG to 80 and 75 wt% respectively, lowered the sheet resistance to 17 and 9 Ω/sq, respectively. For the mechanical properties, we found that adding 10 wt% NG to 90 wt% NFC of sample HH2 (5 mmol NaClO SP-NFC homogenised for 60 min) improved the tensile index by 28 %, tensile stiffness index by 20 %, and peak load by 28 %. The film’s surface morphology was visualised using scanning electron microscopy, revealing the fibrillated structure of NFC and NG. This methodology yields NFC–NG films that are mechanically stable, bendable, and flexible.     

Key role of the hemicellulose content and the cell morphology on the nanofibrillation effectiveness of cellulose pulps

The effect of the hemicellulose content and that of the fibre morphology on the nanofibrillation behaviour of delignified cellulose pulps were studied. For this purpose, pulps from two non-woody plants, alfa (Stipa tenacissima) and sunflower (Helianthus annuus), were delignified using NaClO₂/acetic acid and the NaOH pulping processes to obtain fibres with different hemicellulose contents. The ensuing fibres were characterized by chemical analysis, SEM, FTIRS and X-ray diffraction. The fibres were then disintegrated into nanofibrillated cellulose (NFC) using either a high pressure homogenizer or a domestic blender. The degree of fibrillation and the morphology of the nanofibrillated fractions were evaluated by centrifugation and Field-emission scanning electron microscopy. Pulps containing the highest hemicellulose content showed higher yields of the nanofibrillated fraction and a better aptitude for the individualization of the microfibrils. Furthermore, it was shown that fibres from sunflowers exhibiting a thinner cell wall were easier to fibrillate and could be disintegrated into NFC by just using a simple domestic-blender once deliginification process was carried out using the NaClO₂/acetic acid method. Eucalyptus fibres were also used to further confirm the key role of hemicelluloses in the nanofibrillation process of woody plants.     

CE Method with Partial Filling Techniques for Screening of Xanthine Oxidase Inhibitor in Traditional Chinese Medicine

A combination of electrophoretically mediated microanalysis (EMMA) methodology with a partial filling technique was developed for screening of xanthine oxidase (XOD) inhibitors in substances used in traditional Chinese medicine (TCM). In order to achieve sufficient separation, a micellar electrokinetic chromatography (MEKC) method was employed for the separation. The enzyme activity was determined by the quantification of the peak area of the product, uric acid (UA), at 295 nm. Enzyme inhibition can be read out directly from the reduced peak area of UA in comparison to a reference electropherogram obtained in the absence of any inhibitor. The method was validated using a commercially available XOD inhibitor, 4-aminopyrazolo[3,4-d]pyrimidine, and the IC₅₀ value was determined to be 29.90 ± 0.26 μM. Fifteen natural extracts from TCM were screened, and Cortex Phellodendri (the dried bark of Phellodendron chinense) extract was found to be positive for XOD inhibition.     

Green Synthesis of Silver Nanoparticles Using Water Extract from Galls of <Emphasis Type="Italic">Rhus Chinensis</Emphasis> and Its Antibacterial Activity

The green synthesis of silver nanoparticles (AgNPs) has been proposed as a simple, eco-friendly and cost effective alternative to chemical and physical methods. The Rhus chinensis plant is one of the well studied medicinal plant and its galls find excellent clinical and therapeutic applications. The present study reports the use of water extract from galls of R. chinensis as a reducing agent and formation of AgNPs from silver nitrate solution by a green synthesis route. The AgNPs formation was observed visually by color change and the absorbance peak at 450 nm was observed by UV–Visible spectrophotometer. The shape, size, and morphology of synthesized AgNPs were monitored by transmission electron microscopy and field-emission scanning electron microscopy. The face centered cubic structure of AgNPs was confirmed by X-ray diffraction pattern and element composition by energy dispersive X-ray analysis. The Fourier transform infrared spectroscopy spectrum revealed that the presence of components acts as a reducing and capping agent. The antibacterial activity was performed using the agar well diffusion method. Minimum inhibitory concentration and minimum bactericidal concentration were determined by broth dilution and spread plate method respectively. Synthesized nanoparticles were spotted as triangular and hexagonal shape and the particle size was around 150 nm.     

Creating cellulose fibres with excellent UV protective properties using moist CF4 plasma and ZnO nanoparticles

Weakly ionised gaseous plasma created in a moist tetrafluoromethane gas at a low pressure with an electrodeless radiofrequency discharge was applied to modify the surface properties of cellulose fibres. The plasma was used to increase the adsorption of zinc oxide (ZnO) nanoparticles such that cellulose fibres with good ultraviolet (UV) protective properties could be created. The UV protection factor (UPF) values of the ZnO-functionalised fibres were determined as a function of the plasma treatment time. The chemical and physical surface properties of the plasma-treated fibres were examined using scanning electron microscopy, X-ray photoelectron spectroscopy, and wettability tests. The quantity of zinc on the fibres was determined using inductively coupled plasma mass spectroscopy. The results indicated that 30 s of plasma treatment resulted in ZnO-functionalised samples with lower UPF values than samples without plasma treatment due to the creation of fluorine-rich functional groups on cellulose fibres and the agglomeration of ZnO nanoparticles. The highest UPF values (50+) were obtained when samples were treated with plasma for 10 s. These high UPF values were a result of the increased adsorption of uniformly distributed ZnO nanoparticles caused by fibres surface functionalization and roughening upon plasma treatment. Furthermore, the mechanical properties of textiles treated with moist CF₄ plasma for 10 s were slightly improved.     

On the determination of crystallinity and cellulose content in plant fibres

A comparative study of cellulose crystallinity based on the sample crystallinity and the cellulose content in plant fibres was performed for samples of different origin. Strong acid hydrolysis was found superior to agricultural fibre analysis and comprehensive plant fibre analysis for a consistent determination of the cellulose content. Crystallinity determinations were based on X-ray powder diffraction methods using side-loaded samples in reflection (Bragg-Brentano) mode. Rietveld refinements based on the recently published crystal structure of cellulose Iβ followed by integration of the crystalline and amorphous (background) parts were performed. This was shown to be straightforward to use and in many ways advantageous to traditional crystallinity determinations using the Segal or the Ruland–Vonk methods. The determined cellulose crystallinities were 90–100 g/100 g cellulose in plant-based fibres and 60–70 g/100 g cellulose in wood based fibres. These findings are significant in relation to strong fibre composites and bio-ethanol production.     

Bacterial cellulose films: influence of bacterial strain and drying route on film properties

Structural properties of bacterial cellulose (BC) depend on the microstructure of the material, which in turn is influenced by the bacterial strain. This paper reports the production of BC thin films from two bacterial strains, gluconacetobacter xylinus (GX) and gluconacetobacter europaeus (GE), and three methods of drying the films; at room temperature, freeze drying and supercritical drying. The porosity, transparency, water absorption capacity (WAC) and mechanical properties of the obtained films are further investigated. We conclude that materials with different properties can be fabricated by selecting the bacterial strain or the drying method. Supercritical drying of films of GE achieved mechanically robust and extremely light films, 0.05 g/mL, with up to 96 % of porosity, and with a WAC up 110 times their dried weight. We determined that materials resulting from GE strain are not much affected by the drying method. On the other hand, GX produced BC films more sensitive to the drying method used. Films are denser, 0.6–0.2 g/mL, with tunable porosity from 60 to 90 % and their maximum WAC is 66 times their dried weight.     

Simultaneous determination of four 5-hydroxy polymethoxyflavones by reversed-phase high performance liquid chromatography with electrochemical detection

Accumulating evidence has suggested the potential health-promoting effects of 5-hydroxy polymethoxyflavones (5-OH-PMFs) naturally existing in citrus genus. However, research efforts are hampered by the lack of reliable and sensitive methods for their determination in plant materials and biological samples. Using reversed-phase high performance liquid chromatography (HPLC) equipped with electrochemical (EC) detection, we have developed a fast and highly sensitive method for quantification of four 5-OH-PMFs, namely 5-hydroxy-6,7,8,3′,4′-pentamethoxyflavone, 5-hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone, 5-hydroxy-6,7,4′-trimethoxyflavone, and 5-hydroxy-6,7,8,4′-tetramethoxyflavone. The method was fully validated in terms of linearity, accuracy and precision. The limit of detection (LOD) was determined as being between 0.65 and 1.8 ng/mL (ppb), demonstrating an over 160 times higher sensitivity in comparison with the previously reported method using UV detection. The recovery rate of the method was between 96.17% and 110.82%, and the precision for the retention times and peak areas was all below 13%. The method was successfully used to quantify 5-OH-PMFs with a wide range of abundance in the citrus products and preparations, such as orange juice, citrus peel, and dried tangerine peel. The quantification method for 5-OH-PMFs developed herein could be useful for the nutritional and pharmacological studies of these compounds in future.     

Direct enzymatic esterification of cotton and Avicel with wild-type and engineered cutinases

In this work, the surface of cellulose, either Avicel or cotton fabric, was modified using cutinases without any previous treatment to swell or to solubilise the polymer. Aiming further improvement of cutinase ester synthase activity on cellulose, an engineered cutinase was investigated. Wild-type cutinase from Fusarium solani and its fusion with the carbohydrate-binding module N1 from Cellulomonas fimi were able to esterify the hydroxyl groups of cellulose with distinct efficiencies depending on the acid substrate/solvent system used, as shown by titration and by ATR-FTIR. The carbonyl stretching peak area increased significantly after enzymatic treatment during 72 h at 30 °C. Cutinase treatment resulted in relative increases of 31 and 9 % when octanoic acid and vegetable oil were used as substrates, respectively. Cutinase-N1 treatment resulted in relative increases of 11 and 29 % in the peak area when octanoic acid and vegetable oil were used as substrates, respectively. The production and application of cutinase fused with the domain N1 as a cellulose ester synthase, here reported for the first time, is therefore an interesting strategy to pursuit.     

Preparation, characterization, and antimicrobial property of cotton cellulose fabric grafted with poly (propylene imine) dendrimer

Two generations of poly (propylene imine) dendrimer with amino terminated groups (G2- and G5-PPI-NH₂) were grafted on cotton cellulose fabric using cross linking agents (citric or glutaric acids). Fourier transform infrared (FTIR) spectroscopy identified ester groups which were formed between hydroxyl groups of the cotton fabric and carboxylic groups of the cross linking agents. Also, attenuated total reflectance-FTIR (ATR-FTIR) analysis confirmed formation of amide groups between the carboxylic groups of the cross linking agents and the amino end groups of the dendrimers. Nitrogen content (N-content) analysis revealed the presence of the dendrimers on the cotton fabric even after 5 washing cycles. In order to study the dispersion of the PPI dendrimers on the surface of the cotton fabric, field emission scanning electron microscopy (FE-SEM) was performed. The particle size distribution of the G2- and G5-PPI-NH₂ aqueous solutions was also determined by dynamic light scattering (DLS) analysis. Antimicrobial activity of the PPI dendrimer aqueous solutions and the cotton cellulose fabric grafted with the dendrimers was evaluated both quantitatively and qualitatively against Gram-positive bacterium (Staphylococcus aureus), Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli) and fungus (Candida albicans). The dendrimer grafted cotton cellulose fabric exhibited a 99 % reduction in bacterial counts against S. aureus, E. coli and C. albicans. The antimicrobial activities of the grafted cotton cellulose fabric with the PPI dendrimers were maintained even after 5 washing cycles.