Polyhexamethylene Biguanidine Research Articles

Versatile Magnetic Mesoporous Carbon Derived Nano-Adsorbent for Synchronized Toxic Metal Removal and Bacterial Disinfection from Water Matrices.

Contamination of water resources by toxic metals and opportunistic pathogens remains a serious challenge. The development of nano-adsorbents with desired features to tackle this problem is a continuously evolving field. Here, magnetic mesoporous carbon nanospheres grafted by antimicrobial polyhexamethylene biguanidine (PHMB) are reported. Detailed mechanistic investigations reveal that the electrostatic stabilizer modified magnetic nanocore interfaced mesoporous shell can be programmatically regulated to tune the size and related morphological properties. The core-shell nano-adsorbent shows tailorable shell thickness (≈20-55nm), high surface area (363.47 m2 g-1 ), pore volume (0.426 cm3 g-1 ), radially gradient pores (11.26nm), and abundant biguanidine functionality. Importantly, the nano-adsorbent has high adsorption capacity for toxic thallium (Tl(I) ions (≈559mg g-1 ), excellent disinfection against Staphylococcus aureus and Escherichia coli (>99.99% at 2 and 2.5µg mL-1 ), ultrafast disinfection kinetics rate (>99.99% within ≈4min), and remarkable regeneration capability when exposed to polluted water matrices. The Tl(I) removal is attributed to surface complexation and physical adsorption owing to open ended mesopores, while disinfection relies on contact of terminal biguanidines with phospholipid head groups of membrane. The significance of this work lies in bringing up effective synchronic water purification technology to combat pathogenic microorganisms and toxic metal.

Synergistic strategy constructed hydrogel-aerogel biphase gel (HAB-gel) with self-negative-pressure exudate absorption, M2 macrophage‐polarized and antibacterial for chronic wound treatment

Chronic wound healing is a major and unmet challenge, due to contamination of exudate, bacterial infection and non-healing symptoms, having become urgent an problem to be solved. Developing multifunctional dressings capable of efficiently absorbing exudate by forming self-micro-negative pressure, effectively antibacterial and inducing immune regulation, would be a promising strategy for wound healing. Herein, the hydrogel-aerogel biphase gel (HAB-gel) dressing consisted of PVA grafted with PAM and bio-based polyurethane was prepared to generate synergistic therapeutic effects through removing exudates, antibacterial properties and immune regulation. The PVA grafted with PAMs features generating self-negative pressure to absorb deep exudate by aerogel phase, providing a comfortable microenvironment for wound healing, moreover, the capacities of liquid absorption and retention are enhanced by hydrogel phase, preventing wounds from exudate contamination. The incorporation of β-cyclodextrin (β-CD) in the constructed polyurethane (LPU) endows the HAB-gel materials with excellent antibacterial properties after being loaded with polyhexamethylene biguanidine (PHMB). Furthermore, the HAB-gel dressing can accelerate the macrophage polarization into anti-inflammatory M2 via the hydrogen sulfide (H2S) generation, angiogenesis promotion and collagen deposition in periwound tissue. Overall, this novel strategy for synergistic treatment of chronic wounds, provides a promising method for the management of tissue regeneration disorders.

Effect of hydrochloric polyhexamethylene guanidine (PHMGH) and polyhexamethylene biguanidine (PHMBH), also in combination with plant essential oils and ZnO nanoparticles on some eukaryotic cattle and pig cells

Aim. To investigate both toxic (hemolytic), and stimulating effects of two polymeric derivatives of guani- dine, in particular, polyhexamethylene guanidine (PHMG) and polyhexamethylene biguanidine (PHMB) both in the hydrochloride form, on eukaryotic cells depending on the concentration of the preparation; to study the possibility of using wound-healing and stimulating properties of these preparations in veterinary medicine. Methods. The hemolytic activity (toxicity) of PHMGH and PHMBH preparations in the concentration of 0.1% towards cattle and pig erythrocytes was determined by titration. Primary cell cultures of fetal kidney cells of calves and piglets were used to determine the influence of PHMGH and PHMBH both alone and in combination with the following biologically active substances: essential oils of Pinus sylvestris, Eucalyptus globulus, Citrus sinensis, Monarda didyma, ZnO nanoparticles (size c. 25 nm), and electrochemically acti- vated water – anolyte (Eh = –800 mV, pH 6.5–7.0). The concentration of the cells in the nutrient medium was determined via photocolorimetry. Results. It was found that depending on the concentration, PHMGH, and PHMBH preparations can cause the lysis of erythrocytes, and stimulate cell proliferative activity, including the formation of a monolayer of kidney cells of calves and piglets They cause hemolysis of cattle erythro- cytes in the concentrations commonly used for disinfection, i.e., about 0.1 %, in the average titers of 1 : 7 for PHMGH and 1 : 2.5 for PHMBH. Therefore, PHMBH shows greater hemolytic (biocidal) activity for cattle erythrocytes than PHMGH (in ≈2.8x). The high molecular weight fraction of PHMBH (M2 ≈ 2,000–7,000 Da) demonstrated a lower (in ≈2.4x) hemolytic activity than the low molecular weight basic fraction (M1 ≈ 500–2,000 Da). The experiments on the kidney cell cultures of pigs and cattle have shown that at non-toxic concentrations (10–5 %) PHMBH can effectively stimulate (from 27 to 65 % increase) the proliferative activ- ity of eukaryotic cells and accelerate the formation of a monolayer of cells. The combinations of PHMGH with some essential oils of medicinal plants also show a good effect (from 52 to 95 % increase), and PHMBH shows a good effect with oil of pine for pig kidney cells (20 % increase) and oil of horsemint for cattle kidney cells (67 % increase). Conclusions. PHMGH and PHMBH can possibly be used in agricultural production not only as disinfectants or antiseptics, but also in wound healing. Although their toxicity is also significant to eukaryotic cells, yet they can possibly be used in veterinary medicine in low concentrations (0.005–0.5 %) for the treatment of wounds of various origin, including burns, in the composition of ointments, gels, bandages, or plasters, which we have presently in investigation.

Polyhexamethylene biguanidine used as a new type sewage sludge conditioning agent: Effect on sludge dewaterability and mechanism

Dewatering is the basic procedure of sludge treatment and disposal, and environmentally friendly and efficient sludge conditioning methods are urgently needed. Polyhexamethylene biguanide (PHMB), a broad-spectrum germicide used in daily life and medicine, was proposed as a sludge conditioning reagent in this paper, and its effect on waste activated sludge (WAS) dewaterability was studied for the first time. Results showed that PHMB can improve sludge dewatering performance, and capillary suction time (CST) and water content (Wc) of dewatered sludge cake was reduced by 78.11% and 13.37% with 100 mg PHMB/g dry sludge (DS). Further investigation revealed that the sludge properties changed pronouncedly after PHMB conditioning, the bound water content decreased from 1.58 g/g DS to 1.29 g/g DS, the particle size (D50) increased from 34.3 μm to 39.2 μm, the zeta potential increased from −20.96 mV to −3.36 mV, and the flowability increased whilst the viscosity decreased. When the dose of PHMB was lower than 50 mg/g DS, it mainly reacted with extracellular polymeric substance (EPS), resulting in a decrease in its content, which was also manifested by the decrease of molecular weights. However, when the dose reached 100 mg/g DS, PHMB would disrupt the cytomembranes of microorganisms and release cellular contents, reflected by a corresponding growth of EPS contents and the intensity of Fourier transform infrared (FTIR) spectrum. And the scanning electron microscope (SEM) images showed that PHMB conditioning made cracks and holes on sludge microstructures. The key mechanism of PHMB improving sludge dewaterability was inferred as “organic molecules disrupting” and “sludge particles flocculating”. These findings demonstrate that PHMB is promising to be a novel, effective, and environmentally friendly sludge conditioning reagent.

Composite membrane of polyguanidine cationic surface for desalination

Abstract Surface positve-charged composite membranes were prepared through two guanidine group containing polymers, polyhexamethylene guanidine (PHMG) and polyhexamethylene biguanidine (PHMB). They were used as aqueous phase monomers in an interfacial polymerization (IP) process reacting with trimesoyl chloride (TMC) on the surface of polysulfone (Psf) ultrafiltration membrane. Piperazine (PIP) provided the best pH adjustment among the chosen regulators. As guanidine groups dissociate in water and bring ammonium cations to membrane surfaces, both polyguanidine endowed membranes reacted with divalent metal cations better compared with Na+ and Li+. The rejection rates were more than 90% for all chosen divalent metal salts. PHMG membranes displayed excellent enrichment of Li+ from a mixed solution of Mg2+ and Li+ salts. The Mg2+/Li+ mass ratio decreased from 60 to 3.7, accompanying a −3.6% rejection to Li+. Although partial guanidine groups participated in the IP reaction, bactericidal rates of membranes were both higher than 99% in Gram-negative E. coli and Gram-positive S. aureus tests.

Застосування культур клітин Sus domesticus для тестування властивостей композицій з полігексаметиленбігуанідином

Застосування культур клітин Sus domesticus для тестування властивостей композицій з полігексаметиленбігуанідином

Three Birds with One Stone: Preventive Protection of Paper Materials by ZnO-PHMB and UV-531 Composite Systems

As the most frequently used archival materials for painting and recording, paper lays the groundwork for the development of prosperous human civilization. However, its susceptibility to three primary factors including external ultraviolet light, increased acidity, and biological pathogens in long-term storage shortens the longevity of paper. Therefore, the protection of paper-based cultural relics is extremely urgent. Inspired by the three adverse factors affecting the protection of cultural relics, we herein propose to combine the ultraviolet absorber 2-hydroxy-4-(octyloxy)benzophenone (UV-531) and alkaline zinc oxide (ZnO) nanoparticles innovatively into the antibacterial agent polyhexamethylene biguanidine hydrochloride (PHMB) to realize the strategy of three birds with one stone for relics protection. This study illustrates that the tensile strength and the folding endurance of different test papers are guaranteed by coating them with the composite reagents, and molds including Mucor, Trichoderma, and Aspergillus niger are effectually sterilized. In addition, a hand-painted Chinese ink-wash painting with beautiful flowers is chosen as the object for simulating cultural relics protection, and negligible color fading is observed in aging experiments. From the perspective of effectiveness, simplicity, and economy, this strategy sheds light on preservative protection of paper-based relics in long-term storage.

Dynamic and quantitative characterization of antagonism within disinfectant mixtures by a modified area-concentration ratio method

The coexistence of various typical disinfectant pollutants has the potential to produce toxicity interaction towards organisms in the environment. A suitable model is necessary to evaluate the interaction quantitatively. Hence, the area-concentration ratio (ACR) method was modified (MACR) by combing confidence intervals to dynamically and quantitatively evaluate the toxicity interactions within disinfectant mixture pollutants. Disinfectant mixtures were designed by the direct equipartition design ray method using three guanidine disinfectants, chlorhexidine diacetate (CD), chlorhexidine (CHL), and polyhexamethylene biguanidine (POL) and one chlorine-containing disinfectant calcium hypochlorite (CAL). The toxicities of the four disinfectants and their mixtures towards Vibrio qinghaiensis sp.-Q67 (Q67) were determined by the time-dependent toxicity microplate analysis method. And the toxicity mechanism was analyzed by determining the effects of four disinfectants and their binary mixtures on the structure of cell, DNA and proteins (Pro) for Q67. The results show that the toxicities of CD and CHL to Q67vary little with time, but POL and CAL show the obvious time-dependent toxicity. The toxicities of CD, CHL and POL to Q67 are significantly stronger than that of CAL at the same exposure time. The toxicities of three binary mixture systems don’t have significant difference in different exposure time. MACR can dynamically, quantitatively and accurately characterize toxicity interactions compared with ACR. According to MACR, the antagonism intensity dynamically changes with the prolongation of exposure time for binary mixture rays of three guanidine disinfectants and CAL, and linearly correlates with the components’ concentration ratios. Four disinfectants all can destroy cell membrane and cause desaturation DNA of test organism, and CAL even can destroy the structure of DNA and protein. The probably reason for the antagonism within binary mixtures is the reaction between guanidine group and ClO-, which is called chemical antaogism.

Polyguanidine-modified adsorbent to enhance marine applicability for uranium recovery from seawater

The marine applicability of adsorbents intended for recovering uranium from seawater is crucial. For such applicability, the materials must exhibit anti-biofouling properties, seawater pH adaptability (pH~8), and salt tolerance. Extracting uranium from seawater is a long-term project; hence, biofouling, high salt concentrations, and weak alkaline environments negatively affect the adsorption of uranium and damage the recovered materials. Most studies on the extraction of uranium from seawater focus on increasing the adsorption capacity of the employed adsorbent, while its marine applicability is neglected. In the present study, three types of guanidine polymer (GP)-modified acrylic fibers were prepared to investigate the impact of the introduced structure on the marine applicability of the fibers. After screening, the introduction of polyhexamethylene biguanidine (PHMB) is observed to produce PAO-PHMB-A, characterized by excellent marine applicability. The enhanced properties include high antimicrobial activity (109 CFU/mL, 99.71%), good salt tolerance, and optimal adsorption at a pH of 8. Owing to the synergistic effect of its functional groups, the PAO-PHMB-A material exhibits excellent adsorption performance (525.89 mg/g), as well as high selectivity and durability. More importantly, long-term marine tests revealed that PAO-PHMB-A shows a remarkable uranium adsorption capacity (30 d, 3.19 mg/g) and excellent antibacterial activity. Considering its excellent marine applicability and good adsorption performance, the PAO-PHMB-A material developed in this work could serve as a potential adsorbent for engineering applications associated with uranium recovery from seawater.

PH-responsive spiropyran-based copolymers and their application in monitoring and antibacterial coatings

Although many multifunctional antibacterial materials have been developed, there are few antibacterial materials that can simultaneously monitor pathogenic bacteria and sterilize efficiently. In this work, pH-responsive spiropyran-based fluorinated copolymers with antibacterial, antifouling and fluorescence performances were prepared. First, the random copolymer of methacrylic acid and 1H,1H,2H,2H-perfluorododecyl acrylate (P(MAA-co-FDA)) were synthesized by RAFT polymerization. Second, spiropyran (SP) was grafted onto P(MAA-co-FDA) to obtain the P(MAA-co-SP-co-FDA) copolymer with fluorescence property. At the third step, the remaining carboxyl groups in the grafted copolymer were complexed with protonated polyhexamethylene biguanidine salt (PHMB) to obtain the P(MAA-co-SP-co-FDA)/PHMB copolymer complex antibacterial materials. The results show that the copolymer complex coatings can effectively inhibit the adhesion of bacteria and release PHMB in a bacterial microenvironment to kill S. aureus and E. coli but remain noncytotoxic. The P(MAA-co-SP-co-FDA) copolymer or its complex with PHMB can open the ring and generate a red fluorescence under acidic conditions produced by bacterial growth and metabolism. In addition, the coatings have good biocompatibility, which may be suitable for medical devices to reduce bacterial infection in vivo and in vitro. The prepared multifunctional materials with excellent anti-adhesion, antimicrobial and fluorescence characters will have a broad application prospect in antibacterial, antifouling and monitoring of medical devices.

In vitro disinfection efficacy and clinical protective effects of common disinfectants against acute hepatopancreatic necrosis disease (AHPND)-causing Vibrio isolates in Pacific white shrimp Penaeus vannamei.

Acute hepatopancreatic necrosis disease (AHPND) is one of the most significant bacterial diseases in global shrimp culture, causing severe economic losses. In the present study, we carried out in vitro antimicrobial tests to investigate the disinfection efficacy of 14 common disinfectants toward different AHPND-causing Vibrio spp., including eight isolates of V. parahaemolyticus, four isolates of V. campbellii, and one isolate of V. owensii. Polyhexamethylene biguanidine hydrochloride (PHMB) was revealed to possess the strongest inhibitory activity. Through analyzing and evaluating the results of antimicrobial tests and acute toxicity test, we selected PHMB and hydrogen peroxide (H2O2) for further clinical protection test. Clinical manifestations indicated that both PHMB (2 mg/L and 4 mg/L) and H2O2 (12 mg/L) could effectively protect juvenile Penaeus vannamei from the infection of V. parahaemolyticus isolate Vp362 at 106 CFU/ml, and the survival rate was over 80%. When the bacterial concentration was reduced to 105 CFU/ml, 104 CFU/ml, and 103 CFU/ml, the survival rate after treated by 1 mg/L PHMB was 64.44%, 93.33%, and 100%, respectively. According to the results, PHMB and H2O2 showed a lower toxicity while a better protection activity, particularly against a lower concentration of the pathogens. Therefore, these two disinfectants are proved to be promising disinfectants that can be applied to prevent and control AHPND in shrimp culture. Moreover, the methods of this study also provided valuable information for the prevention of other important bacterial diseases and suggested a reliable means for screening potential drugs in aquaculture.

Highly transparent, highly flexible composite membrane with multiple antimicrobial effects used for promoting wound healing

In recent years, bacterial cellulose (BC)-based dressings or patches for skin or soft tissue repair have become investigative emphasis. However, most of the BC-based products used for biomedical applications present limitations due to their low flexibility, poor gas permeability and no inherent antibacterial activity. Herein, we proposed and designed a novel composite composed of natural bacterial cellulose (BC), polyethylene glycol (PEG) and polyhexamethylene biguanidine (PHMB) through new synthetic approaches. The composite membrane exhibited favorable physicochemical performance, especially transparency, water retention ability, flexibility as well as the characteristic of anti-adhesion. In vitro biochemical experiment results indicated that the composite had excellent biocompatibility and exhibited strong and sustained antibacterial effect. In vivo test further demonstrated that the composite could efficiently promote skin wound healing and regeneration in a rat model. This composite membrane possesses multiple mechanisms of promoting cutaneous wound healing and will provide new ideas for future development of wound dressings.

Development of effective and safe compound disinfectant for space cabins

Space-enclosed cabins such as space stations provide a suitable living environment for astronauts, meanwhile they also facilitate various microorganisms to breed and corrode the materials' surfaces. To effectively prevent and control the microbial contamination in space-closed cabins and ensure the health of the astronauts, it is necessary to develop effective and safe disinfectants. In this study, organosilicon quaternary ammonium salt(OQAS), sodium dehydroacetate (SD) and polyhexamethylene biguanidine hydrochloride(PHMB) were selected as the target disinfectants and tested on four kinds of corrosive fungi, including Cladosporium cladosporioides, Aspergillus niger, Penicillium aurantiogriseum and Cladosporium herbarum. Firstly, the mycelial growth inhibition effects of these three disinfectants on the four fungi were tested separately, and the effective concentration range of the three disinfectants were determined. Then we combined these three disinfectants to get a new highly effective and safe compound bactericides, consisting of OQAS (0.37 mg/ml), SD (0.7 mg/ml) and PHMB (0.5 mg/ml), in which the total concentrations of bactericides were 1.57 mg/ml. This study provided a new perspective for the development of safe microbial bacteriostatic agents in spacecraft.

Influence of polymeric derivatives of guanidine on hydrobionts

It is known that polymeric derivatives of guanidine are actively used in many countries of the world as disinfectants and antiseptics. Polyhexamethylene guanidine (PHMG) and polyhexamethylene biguanidine (PHMB) are typical representatives of this class of compounds. They show a bacteriostatic effect in concentrations from 1 mg/l (or 10–4%) or above, and a bactericidal effect from 10 mg/l (10–3%) and above. It is considered that PHMG and PHMB are not very toxic to higher organisms. This is explained by the different mechanism of drugs action on prokaryotic and eukaryotic cells. However, their safety for the fauna of freshwater hydrocenoses has not been sufficiently studied. The toxic effect of the salts of PHMG on the representatives of various types and classes of hydrobionts was studied in the experiments. It has been established that the safe concentration of PHMG in water with a one-time action on selected test objects is 0.1 mg/l (10–5%). The histological analysis of a one-year-old carp that lived in an aquarium with a constant concentration of PHMG at 0.5 mg/l for 12 days showed that concentrations of an order of magnitude smaller – 0.01 mg/l (10–6%) is absolutely safe to consider. Chronic intoxication of fish caused by sublethal doses of PHMG leads to the development of numerous disorders in the liver, kidneys, and spleen, and to the inflammation of the pancreatic islets. A comparative analysis of the toxicity of PHMG for microand macroorganisms does not allow us to state that the latter are less sensitive to this xenobiotic. So far, there are not enough convincing reasons to believe that the mechanisms of action of PHMG on pro and eukaryotic cells are fundamentally different. At the same time, the binding of PHMG molecules to suspended particles in water, organic and inorganic impurities, flocculation, and biodegradation by microorganisms leads to a rapid decrease of free active molecules of this biocide in aquatic ecosystems.

Mussel-inspired functionalization of PEO/PCL composite coating on a biodegradable AZ31 magnesium alloy

The rapid degradation of magnesium-based implants in physiological environments in vivo not only will quickly deteriorate their mechanical strengths but will also lead to a severe change of the micro-environment around the implants, which may cause the final failure of magnesium-based implants. In this work, a polycaprolactone (PCL) layer was prepared to seal the plasma electrolytic oxidization coating (PEO) to form a PEO/PCL composite coating on a biodegradable AZ31 magnesium alloy, followed by further surface functionalization with polydopamine. The in vitro degradation behaviors of the bare AZ31 alloy and coated samples were evaluated in a simulated body fluid (SBF) using the potentiodynamic polarization curve test and the static immersion test. The bioactivity of the samples was investigated using the SBF soaking test. The cytocompatibility of all samples was evaluated using the cytotoxicity test and analysis of the adhesion and proliferation of osteoblast cells (MC3T3-E1) directly cultivated on the sample surface. The results showed that the PCL layer successfully sealed the pores of the PEO coating, and then the polydopamine layer formed on its surface. The in vitro degradation tests showed that the PEO/PCL composite coating improved the corrosion resistance of the AZ31 alloy in SBF with a more positive corrosion potential and a lower corrosion current density. Due to the protection of the PEO/PCL composite coating, the surrounding environment showed nearly no influence on the degradation of the coated sample, which led to no obvious local alkalization and hydrogen evolution. Moreover, compared with the AZ31 alloy and PEO coating, the PEO/PCL composite coating was more suitable for cell adhesion and proliferation. After further surface functionalization by polydopamine, the corrosion resistance of the composite coating was maintained, while its bioactivity was significantly enhanced with a large amount of hydroxyapatite (HA) formed on its surface after immersion in SBF. The initial cell adhesion and spread were also improved by the polydopamine. By further immobilizing polyhexamethylene biguanidine (PHMB) onto the coating surface via the assistance of polydopamine, good antibacterial ability was obtained. This feasible method for fabricating a cytocompatible and antibacterial composite coating on a biodegradable AZ31 alloy may be promising in implant applications due to the osteointegration and anti-infection properties of these materials post operation.

Polyhexamethylene biguanidine induce pulmonary inflammatory responses

Polyhexamethylene biguanidine induce pulmonary inflammatory responses

Catalytically active and hierarchically porous SAPO-11 zeolite synthesized in the presence of polyhexamethylene biguanidine

Hierarchically porous SAPO-11 zeolite (H-SAPO-11) is rationally synthesized from a starting silicoaluminophosphate gel in the presence of polyhexamethylene biguanidine as a mesoscale template. The sample is well characterized by XRD, N2 sorption, SEM, TEM, NMR, XPS, NH3-TPD, and TG techniques. The results show that the sample obtained has good crystallinity, hierarchical porosity (mesopores at ca. 10nm and macropores at ca. 50–200nm), high BET surface area (226m2/g), large pore volume (0.25cm3/g), and abundant medium and strong acidic sites (0.36mmol/g). After loading Pt (0.5wt.%) on H-SAPO-11 by using wet impregnation method, catalytic hydroisomerization tests of n-dodecane show that the hierarchical Pt/SAPO-11 zeolite exhibits high conversion of n-dodecane and enhanced selectivity for branched products as well as reduced selectivity for cracking products, compared with conventional Pt/SAPO-11 zeolite. This phenomenon is reasonably attributed to the presence of hierarchical porosity, which is favorable for access of reactants on catalytically active sites. The improvement in catalytic performance in long-chain paraffin hydroisomerization over Pt/SAPO-11-based catalyst is of great importance for its industrial applications in the future.

Structural Characterization and Bacteriostatic and Cytotoxicity to 3T3 Cells Study of Oligobiguanidine (Polyhexamethylene Biguanidine Hydrochloride) and its 3-Glycidoxypropyltrimethoxysilane Derivatives

In this paper, polyhexamethylene biguanidine hydrochloride (PHMB) oligomers were prepared by polycondensation of hexamethylenediamine, hydrochloric acid and 1,6-hexamethylenebis(dicyanamide); the organosilicon derivatives of PHMB oligomers (PHMB-Si) were prepared in solution through the reaction of PHMB and 3-Glycidoxypropyltrimethoxysilane (GLYMO). The analyses of FT-IR, 1H and 13C-NMR, elemental analysis, and TGA showed that the PHMB-Si was synthesized successfully. The relationship between antibiotic activity and viscosity-average molecular weight of PHMB; the relationship between antibiotic activity and the content of organosilicon in PHMB-Si were investigated. The experimental results revealed that the antibacterial activity of PHMB yielded the maximum at the viscosity-average molecular weight of 9000. The higher ratio of GLMYO in PHMB-Si, the higher antibiotic activity of PHMB-Si was. The minimal bactericidal concentration (MBC) of PHMB was 10 ppm, and the MBC of PHMB-Si was 5 ppm. The results showed there was an obvious synergy of PHMB-Si in bacteriostatic activity than PHMB.

GRAS (GENERALLY RECOGNIZED AS SAVE) METHODS AS A POSSIBLE CONTROL OF POSTHARVEST FUNGAL DISEASES IN SWEET CHERRY

Sweet cherry is a fruit with a very limited storage life and fungal decay during shelf-life can often result in serious fruit loss. In Germany, there are no postharvest treatments allowed to control fungal diseases on sweet cherries. However, internationally interest is increasing in alternative methods that are harmless to consumer health. We tested different GRAS (Generally Recognized As Safe) methods to control Penicillium expansum (blue mould rot), Botrytis cinerea (gray mould rot) and Monilinia fructigena (brown rot) on sweet cherry in 2007 and 2008. Comparing the different GRAS methods, a combination of sodium bicarbonate (NaHC0 3 ) and yeast (Aurebasidium pullulans), a product marketed as Antinfek ™ 10H (polyhexamethylene biguanidine hydrochloride 3.2% w/w) a combination of Antinfek ™ with Serenade Max (Bacillus subtilis), and Antinfek ™ with calcium hydroxide, all showed good results in reducing postharvest fungal diseases. Other GRAS methods, such as citric acid, calcium formate, Na-metasilicate, chitosan, or yeast separately did not show adequate control against the tested fungi. Further GRAS research to control post-harvest diseases in sweet cherry is planned.

Synthesis and antimicrobial activity of polymeric guanidine and biguanidine salts

Polyhexamethylene guanidine hydrochloride and polyhexamethylene biguanidine hydrochloride were polycondensated in the melt of monomers. The intrinsic viscosity and M ̄ n were determined by the viscosity of dilute polymer solution and VPO, respectively. Polyhexamethylene guanidine stearate and polyhexamethylene biguanidine stearate were synthesized using the precipitation reaction for the first time. NMR, FTIR, XPS and element analysis were used to analyze the chemical structure and element composition. The structure of the resultant polymers is coincident with the theoretic structure. The minimal inhibition concentration (MIC) was measured to characterize the antimicrobial activity of the products. The MIC is not larger than 200 μg ml −1. The polymeric guanidine and biguanidine are effective in controlling bacteria and fungi. The TG test shows that the resultant polymers are stable to heat.