Innovative material containing the natural product curcumin, with enhanced antimicrobial properties for active packaging

Antibacterial activity of curcumin and its essential nanoformulations against some clinically important bacterial pathogens: A comprehensive review

Multidrug-resistant bacterial infections can kill 700,000 individuals globally each year and is considered among the top 10 global health threats faced by humanity as the arsenal of antibiotics is becoming dry and alternate antibacterial molecule is in demand. Nanoparticles of curcumin exhibit appreciable broad-spectrum antibacterial activity using unique and novel mechanisms and thus the process deserves to be reviewed and further researched to clearly understand the mechanisms. Based on the antibiotic resistance, infection, and virulence potential, a list of clinically important bacteria was prepared after extensive literature survey and all recent reports on the antibacterial activity of curcumin and its nanoformulations as well as their mechanism of antibacterial action have been reviewed. Curcumin, nanocurcumin, and its nanocomposites with improved aqueous solubility and bioavailability are very potential, reliable, safe, and sustainable antibacterial molecule against clinically important bacterial species that uses multitarget mechanism such as inactivation of antioxidant enzyme, reactive oxygen species-mediated cellular damage, and inhibition of acyl-homoserine-lactone synthase necessary for quorum sensing and biofilm formation, thereby bypassing the mechanisms of bacterial antibiotic resistance. Nanoformulations of curcumin can thus be considered as a potential and sustainable antibacterial drug candidate to address the issue of antibiotic resistance.

Zinc-curcumin based complexes in health and diseases: An approach in chemopreventive and therapeutic improvement

Curcumin, a polyphenolic compound isolated from turmeric rhizome, displays antioxidant, anti-inflammatory, anticancer, anti-microbial, antiviral, antidiabetic, neuroprotective, immune boosting and other chemopreventive and therapeutic properties. However, the efficacy of curcumin is confined due to its aqueous insolubility, instability, low intestinal absorption, poor bioavailability, and systemic elimination. Therefore, to overcome these issues and enhance pharmacological activities of curcumin, a complex of curcumin with metals such as zinc have been synthesized. Curcumin acts as a ligand and forms a stable complex with zinc. In this review, the improved protective, and therapeutic activities of zinc-curcumin complexes are discussed. Zinc-curcumin conjugates have exhibited enhanced antioxidant, anti-inflammatory, anticancer, antimicrobial and antidiabetic properties. Zinc-curcumin complexes have also displayed hepatoprotective, gastroprotective, neuroprotective, cardioprotective and osteogenesis efficacy. These protective and therapeutic efficacies of zinc-curcumin conjugates were associated with modulation of multiple molecular mechanisms including decreased inflammatory cytokines, increased antioxidant enzymes, quenched free radicals, decreased blood glucose levels, decreased insulin resistance, induced apoptosis markers, and restored function of tumor suppressor protein p53 in cancer cells. Overall, applications of zinc-curcumin complex could be a new approach against various diseases and could also be helpful in improvement of health.

Innovative Bacterial Removal Technique Using Green Synthetic Nano Curcumin Zinc (II) Complex for Sustainable Water Resource Management

Sustainable management of water resources is a daunting challenge, especially with respect to microbes. This study primarily focused on the development of a novel application for the removal of specific bacterial groups in different water types using a green synthetic nano Cur-Zn(II) complex. The results of UV and FT-IR spectroscopic techniques suggested the formation of a chelation complex. Proton NMR showed that the main enolic proton peak with a chemical shift of 16.45 nm identified in curcumin was missed, indicating the contribution of carbonyl oxygen of enol in the formation of the complex. The crystalline nature of the complex and Wurtzite structure of annealed products was inferred from the XRD analysis data. SEM results confirmed the complex’s morphology as spherical and clustered with a rough surface, having an average particle size of 68.2 nm. In addition, the complex was observed to be stable up to 300 °C without any decomposition from STA. Being acidic in nature with a pH of 5.36, the complex penetrates into the cell membrane and inhibit microbial growth. Intrinsically, no studies have been reported for the removal of microbes from water using natural materials embedded with inorganic metals, particularly in nano form. Therefore, the study is the first, innovative, eco-friendly, and economical method to use nano Cur-Zn(II) for removing targeted bacteria in real water samples with 100% efficiency by using optimized amounts (0.025–0.2 g/L) of the complex at a contact time interval between 4 and 24 h. The complex developed is toxic-free and can be applied in situ.

Preparation, characterization and application of poly(lactic acid)/corn starch/eucalyptus leaf essential oil microencapsulated active bilayer degradable film

This study aimed to develop a composite bilayer film based on corn starch (CS)/polylactic acid (PLA). The film had a hydrophobic outer layer and an absorbent inner layer. A natural bioactive substance was incorporated into the inner layer, namely, eucalyptus essential oil microcapsules (EOM). This allowed most of the bioactive substance to be released inside the storage environment. The effects of different amounts of EOM on the physical, mechanical, antioxidant, and antimicrobial properties of the films were investigated. Based on the results of scanning electron microscopy (SEM), the addition of 10-15 mL/100 mL of EOM could be uniformly distributed in the film. The addition of less than 15 mL/100 mL of EOM to the film improved its tensile strength, barrier properties, and elongation at break. The addition of too much EOM led to cracks in the film. The addition of EOM also greatly improved the antioxidant and antibacterial properties of the bilayer film. The best performance was obtained when the added amount was 15 mL/100 mL. Films with the best overall properties were used for preserving Agaricus bisporus. In preservation experiments, this film inhibited the respiration rate of A. bisporus, slowed down the consumption of organic matter, and maintained its moisture content. Compared with other cling films, the shelf life of A. bisporus was greatly extended.

Application of Nanotechnology to Improve the Performance of Biodegradable Biopolymer-Based Packaging Materials

There is great interest in developing biodegradable biopolymer-based packaging materials whose functional performance is enhanced by incorporating active compounds into them, such as light blockers, plasticizers, crosslinkers, diffusion blockers, antimicrobials, antioxidants, and sensors. However, many of these compounds are volatile, chemically unstable, water-insoluble, matrix incompatible, or have adverse effects on film properties, which makes them difficult to directly incorporate into the packaging materials. These challenges can often be overcome by encapsulating the active compounds within food-grade nanoparticles, which are then introduced into the packaging materials. The presence of these nanoencapsulated active compounds in biopolymer-based coatings or films can greatly improve their functional performance. For example, anthocyanins can be used as light-blockers to retard oxidation reactions, or they can be used as pH/gas/temperature sensors to produce smart indicators to monitor the freshness of packaged foods. Encapsulated botanical extracts (like essential oils) can be used to increase the shelf life of foods due to their antimicrobial and antioxidant activities. The resistance of packaging materials to external factors can be improved by incorporating plasticizers (glycerol, sorbitol), crosslinkers (glutaraldehyde, tannic acid), and fillers (nanoparticles or nanofibers). Nanoenabled delivery systems can also be designed to control the release of active ingredients (such as antimicrobials or antioxidants) into the packaged food over time, which may extend their efficacy. This article reviews the different kinds of nanocarriers available for loading active compounds into these types of packaging materials and then discusses their impact on the optical, mechanical, thermal, barrier, antioxidant, and antimicrobial properties of the packaging materials. Furthermore, it highlights the different kinds of bioactive compounds that can be incorporated into biopolymer-based packaging.

A balanced charged hydrogel with anti-biofouling and antioxidant properties for treatment of irradiation-induced skin injury

Skin injury caused by large doses of ionizing radiation is the common and severe side effect of radiotherapy. However, its therapeutic efficacy is always hindered by early reactive oxygen species generation, repetitive inflammatory microenvironment and bacterial infection risk. Herein, we report an anti-biofouling hydrogel with anti-inflammation and anti-oxidative properties for the treatment of irradiation-induced skin injury. The anti-biofouling hydrogel can be achieved by balancing oppositely charged alginate, hyaluronic acid (HA) and polylysine (PLL) at the optimal ratio, which effectively resist protein and bacterial adhesion, and evades immune response. Moreover, curcumin and epigallocatechin gallate (EGCG) can be facially encapsulated and substantially released from the hydrogel. Results showed that the resulting AHP-Cur/EGCG hydrogel can significantly weaken the development of skin injury and accelerate its healing process by alleviating inflammation, scavenging ROS and promoting angiogenesis. Therefore, the findings presented in this work provide an effective strategy for clinical management and treatment of ionizing radiation-induced skin injury.

Silver Nanoparticles Using Eucalyptus or Willow Extracts (AgNPs) as Contact Lens Hydrogel Components to Reduce the Risk of Microbial Infection

Eucalyptus leaves (ELE) and willow bark (WBE) extracts were utilized towards the formation of silver nanoparticles (AgNPs(ELE), AgNPs(WBE)). AgNPs(ELE) and AgNPs(WBE) were dispersed in polymer hydrogels to create pHEMA@AgNPs(ELE)_2 and pHEMA@AgNPs(WBE)_2 using hydroxyethyl-methacrylate (HEMA). The materials were characterized in a solid state by X-ray fluorescence (XRF) spectroscopy, X-ray powder diffraction analysis (XRPD), thermogravimetric differential thermal analysis (TG-DTA), differential scanning calorimetry (DTG/DSC) and attenuated total reflection spectroscopy (ATR-FTIR) and ultraviolet visible (UV-vis) spectroscopy in solution. The antimicrobial potential of the materials was investigated against the Gram-negative bacterial strain Pseudomonas aeruginosa (P. aeruginosa) and the Gram-positive bacterial strain of the genus Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus), which are involved in microbial keratitis. The percentage of bacterial viability of P. aeruginosa and S. epidermidis upon their incubation over the pHEMA@AgNPs(ELE)_2 discs is interestingly low (28.3 and 6.8% respectively), while the inhibition zones (IZ) formed are 12.3 ± 1.7 and 13.2 ± 1.2 mm, respectively. No in vitro toxicity of this material towards human corneal epithelial cells (HCEC) was detected. Despite its low performance against S. aureus, pHEMA@AgNPs(ELE)_2 could be an efficient candidate towards the development of contact lenses that reduces microbial infection risk.

Metal-Curcumin Complexes in Therapeutics: An Approach to Enhance Pharmacological Effects of Curcumin

Curcumin, an active component of the rhizome turmeric, has gained much attention as a plant-based compound with pleiotropic pharmacological properties. It possesses anti-inflammatory, antioxidant, hypoglycemic, antimicrobial, neuroprotective, and immunomodulatory activities. However, the health-promoting utility of curcumin is constrained due to its hydrophobic nature, water insolubility, poor bioavailability, rapid metabolism, and systemic elimination. Therefore, an innovative stride was taken, and complexes of metals with curcumin have been synthesized. Curcumin usually reacts with metals through the β-diketone moiety to generate metal–curcumin complexes. It is well established that curcumin strongly chelates several metal ions, including boron, cobalt, copper, gallium, gadolinium, gold, lanthanum, manganese, nickel, iron, palladium, platinum, ruthenium, silver, vanadium, and zinc. In this review, the pharmacological, chemopreventive, and therapeutic activities of metal–curcumin complexes are discussed. Metal–curcumin complexes increase the solubility, cellular uptake, and bioavailability and improve the antioxidant, anti-inflammatory, antimicrobial, and antiviral effects of curcumin. Metal–curcumin complexes have also demonstrated efficacy against various chronic diseases, including cancer, arthritis, osteoporosis, and neurological disorders such as Alzheimer’s disease. These biological activities of metal–curcumin complexes were associated with the modulation of inflammatory mediators, transcription factors, protein kinases, antiapoptotic proteins, lipid peroxidation, and antioxidant enzymes. In addition, metal–curcumin complexes have shown usefulness in biological imaging and radioimaging. The future use of metal–curcumin complexes may represent a new approach in the prevention and treatment of chronic diseases.

Ciprofloxacin conjugated to diphenyltin(IV): a novel formulation with enhanced antimicrobial activity

The metalloantibiotic of formula Ph2Sn(CIP)2 (CIPTIN) (HCIP = ciprofloxacin) was synthesized by reacting ciprofloxacin hydrochloride (HCIP·HCl) (an antibiotic in clinical use) with diphenyltin dichloride (Ph2SnCl2DPTD). The complex was characterized in the solid state by melting point, FT-IR, X-ray Powder Diffraction (XRPD) analysis, 119Sn Mössbauer spectroscopy, X-ray Fluorescence (XRF) spectroscopy, and Thermogravimetry/Differential Thermal Analysis (TG-DTA) and in solution by UV-Vis, 1H NMR spectroscopic techniques and Electrospray Ionisation Mass Spectrometry (ESI-MS). The crystal structure of CIPTIN and its processor HCIP was also determined by X-ray crystallography. The antibacterial activity of CIPTIN, HCIP·HCl, HCIP and DPTD was evaluated against the bacterial species Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis), by the means of Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Inhibition Zones (IZs). CIPTIN shows lower MIC values than those of HCIP·HCl (up to 4.2-fold), HCIP (up to 2.7-fold) or DPTD (>135-fold), towards the tested microbes. CIPTIN is classified into bactericidal agents according to MBC/MIC values. The developing IZs are 40.8 ± 1.5, 34.0 ± 0.8, 36.0 ± 1.1 and 42.7 ± 0.8 mm, respectively which classify the microbes P. aeruginosa, E. coli, S. aureus and S. epidermidis to susceptible ones to CIPTIN. These IZs are greater than the corresponding ones of HCIP·HCl by 1.1 to 1.5-fold against both the tested Gram negative and Gram positive bacteria. CIPTIN eradicates the biofilm of P. aeruginosa and S. aureus more efficiently than HCIP·HCl and HCIP. The in vitro toxicity and genotoxicity of CIPTIN were tested against human skin keratinocyte cells (HaCaT) (IC50 = 2.33 μM). CIPTIN exhibits 2 to 9-fold lower MIC values than its IC50 against HaCaT, while its genotoxic effect determined by micronucleus assay is equivalent to the corresponding ones of HCIP·HCl or HCIP.

Designing active mats based on cellulose acetate/polycaprolactone core/shell structures with different release kinetics

Core/shell electrospun mats based on cellulose acetate (CA) and polycaprolactone (PCL) were developed as novel active materials for releasing quercetin (Quer) and curcumin (Cur). The effect of polymeric uniaxial and coaxial electrospun systems and the chemical structures of Quer and Cur on the structural, thermal, and mass transfer properties of the developed mats were investigated. Release modelling indicated that the diffusion of the active agents from the uniaxial PCL fibers was highly dependent on the type of food simulant. Higher diffusion coefficients were obtained for both active agents in acid food simulant due to the higher swelling of the electrospun mats. In addition, CA/PCL coaxial structures slowed down the diffusion of both active agents into both food simulants. CA increased the retention of the active compounds in the polymer structure, resulting in partition coefficients values higher than the values obtained for uniaxial active PCL mats.

Tetracycline Water Soluble Formulations with Enhanced Antimicrobial Activity

The negligible water solubility of tetracycline (TC), a well-known antibiotic of clinical use, is the major disadvantage for its oral administration. With the aim to improve the water solubility of TC, the micelles of formulae SLS@TC and CTAB@TC (SLS = sodium lauryl sulphate and CTAB = cetrimonium bromide) were synthesized. The micelles SLS@TC and CTAB@TC were characterized by melting point (m.p.), thermogravimetric differential thermal analysis (TG-DTA), differential scanning calorimetry (DTG/DSC), attenuated total reflection spectroscopy (FT-IR-ATR), ultra-violet visible (UV/vis) spectroscopy, proton nucleus magnetic resonance (1H-NMR) spectroscopy, and the ultrasonically-induced biregringence technique. The antimicrobial activity of SLS@TC and CTAB@TC was evaluated, by means of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and inhibition zone (IZ), against the Gram negative bacterial strains Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli) and the Gram positive ones of the genus of Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus). Generally, both micelles show better activity than that of TC against the microbial strains tested. Thus, the MIC value of CTAB@TC is 550-fold higher than that of free TC against S. epidermidis. Despite the stronger activity of CTAB@TC than SLS@TC against both Gram negative and Gram positive microbes, SLS@TC is classified as a bactericidal agent (in that it eliminates 99.9% of the microbes), in contrast to CTAB@TC, which is bacteriostatic one (inhibits, but does not kill the organisms). The toxicity of SLS@TC and CTAB@TC was evaluated against human corneal eukaryotic cells (HCECs). Moreover, SLS@TC and CTAB@TC exhibit low in vivo toxicity against Artemia salina, even at concentrations up to threefold higher than those of their MICmax. Therefore, SLS@TC and CTAB@TC can be candidates for the development of new antibiotics.

Photodynamic therapry with curcumin in the reduction of enterococcus faecalis biofilm in bone cavity: rMicrobiological and spectral fluorescense analysis

BACKGROUND

Antimicrobial photodynamic therapy (PDT) has emerged as a therapeutic strategy to conventional procedures using antibiotics.

OBJECTIVE

To evaluate the antimicrobial effectiveness of PDT using blue light emitting diode (LED) associated with curcumin on biofilms of Enterococcus faecalis in bovine bone cavities and also to analyze the presence of these biofilms through spectral fluorescence.

MATERIALS AND METHODS

Standardized suspensions of E. faecalis (ATCC 29212) were incubated in artificial bone cavities for 14 days at 36 °C ± 1 °C for biofilm formation. The test specimens were distributed among the four experimental groups (n = 10): L-C- (control), L + C- (LED for 5 min), L-C+ (curcumin for 5 min) and L + C+ (PDT). Aliquots were collected from the bone cavities after treatments and seeded on BHI agar for 24 h at 36 °C ± 1 °C for CFU count. Before and after each treatment the specimens were submitted to spectral fluorescence, whose images were compared in the Image J program. The log10 CFU/mL results were submitted to the Kruskal-Wallis test (5%) and the biofilm fluorescence spectroscopy results were submitted to the Wilcoxon test (5%).

RESULTS

All treatments presented statistical difference when compared to the control, and PDT was responsible for the largest reduction (1.92 log10 CFU/mL). There was a reduction in the fluorescence emitted after the treatments, with greater statistical difference in the PDT group.

CONCLUSION

PDT was efficient in the reduction of E. faecalis biofilms. In all groups post treatment there was a significant reduction of biofilms in the fluorescence spectroscopy images with greater reduction in the PDT group.

Development of curcumin-loaded chitosan/pluronic membranes for wound healing applications

The emergence of new materials with improved antibacterial, anti-inflammatory and healing properties compared to conventional wound dressings has both social and economic appeal. In this study, novel chitosan-based (CTS) membranes containing curcumin (CUR) incorporated in Pluronic (PLU) copolymers were developed and characterized to obtain suitable properties for applications as a wound healing dressing. The mechanical, thermal, swelling, wettability, release and permeation properties were evaluated by DSC, TGA, water contact angle measurements, FTIR, fluorescence and microscopic techniques. Membranes containing PLU and CUR presented wettability close to the ideal range for interaction with cellular components (contact angle ~40-70°), improved mechanical properties, higher thermal stability, high swelling degree (>800%) and CUR release (~60%) compared to samples without PLU addition. A higher retention of CUR in the epidermis than in the dermis layer was observed, which also was confirmed by confocal microscopy. Furthermore, the CTS-PLU membranes loaded with CUR showed to be active against Staphylococcus aureus and Pseudomonas aeruginosa (MIC = 25 and 100 mg mL^-1, respectively), the microbial species most present in chronic wounds. Overall, the CTS-PLU-CUR membranes presented suitable properties to act as a new wound healing dressing formulation and in vivo studies should be performed to confirm these benefits.

pHEMA@AGMNA-1: A novel material for the development of antibacterial contact lens

The Metal Organic Framework (MOF) of formula {[Ag₆(μ₃-HMNA)₄(μ₃-MNA)₂]^2-·[(Et₃NH)⁺]₂·(DMSO)₂·(H₂O)} (AGMNA), a known efficient antimicrobial compound which contains the anti-metabolite, 2-thio-nicotinic acid (H₂MNA), was incorporated in polymer hydrogels using, hydroxyethyl-methacrylate (HEMA). The material pHEMA@AGMNA-1 was characterized by X-ray fluorescence (XRF) spectroscopy, X-ray powder diffraction analysis (XRPD), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), Thermogravimetric Differential Thermal Analysis (TG-DTA), Differential Scanning Calorimetry (DTG/DSC), attenuated total reflection spectroscopy (FT-IR-ATR) and Ultrasonic Imaging. The antimicrobial capacity of pHEMA@AGMNA-1 was evaluated against the Gram negative bacterial strain Pseudomonas aeruginosa and the Gram positive ones of the genus of Staphylococcus epidermidis and Staphylococcus aureus, which are the etiology of the microbial keratitis. The % bacterial viability of P. aeruginosa, S. epidermidis and S. aureus upon their incubation with pHEMA@AGMNA-1 discs is significantly low (0.4 ± 0.1%, 1.5 ± 0.4% and 7.7 ± 0.5% respectively). The inhibition zones (IZ) caused by pHEMA@AGMNA-1 discs against P. aeruginosa, S. epidermidis and S. aureus are 14.0 ± 1.1, 11.3 ± 1.3 and 11.8 ± 1.8 mm respectively. Furthermore, pHEMA@AGMNA-1 exhibits low toxicity. Thus, pHEMA@AGMNA-1 might be an efficient candidate for the development of antimicrobial active contact lenses.

Conjugation of Penicillin-G with Silver(I) Ions Expands Its Antimicrobial Activity against Gram Negative Bacteria

Conjugation of penicillin G (PenH) with silver(I) ions forms a new CoMeD (conjugate of metal with a drug) with formula [Ag(pen)(CH₃OH)]₂ (PenAg). PenAg was characterized by a plethora of physical and spectroscopic techniques, which include in the solid state m.p.; elemental analysis; X-ray fluorescence (XRF) spectroscopy; scanning electron microscopy (SEM); energy-dispersive X-ray spectroscopy (EDX); FT-IR; and in solution: attenuated total reflection spectroscopy (FT-IR-ATR), UV–Vis, ¹H NMR, and atomic absorption (AA). The structure of PenAg was determined by NMR spectroscopy. Silver(I) ions coordinate to the carboxylic group of PenH, while secondary intra-molecular interactions are developed through (i) the nitrogen atom of the amide group in MeOD-d₄ or (ii) the sulfur atom in the thietane ring in deuterated dimethyl sulfoxide DMSO-d₆. The antibacterial activities of PenAg and the sodium salt of penicillin (PenNa) (the formulation which is clinically used) against Gram positive (Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus)) and Gram negative (Pseudomonas aeruginosa (P. aeuroginosa PAO1)) bacteria were evaluated by the means of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and inhibition zone (IZ). PenAg inhibits the growth of the Gram negative bacterial strain P. aeuroginosa with a MIC value of 23.00 ± 2.29 μM, in contrast to PenNa, which shows no such activity (>2 mM). The corresponding antimicrobial activities of PenAg against the Gram positive bacteria S. epidermidis and S. aureus are even better than those of PenNa. Moreover, PenAg exhibits no in vivo toxicity against Artemia salina at concentration up to 300 μΜ. The wide therapeutic window and the low toxicity, make PenAg a possible candidate for the development of a new antibiotic.

Preparation of antimicrobial and antioxidant gelatin/curcumin composite films for active food packaging application

The functional gelatin/curcumin composite film was prepared using an emulsifier, sodium dodecyl sulfate (SDS). The composite films were characterized using field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FTIR). The FE-SEM test results showed that curcumin was evenly distributed in the gelatin polymer matrix to form a flexible composite film with a smooth surface. The addition of 1.5 % of curcumin improved the UV blocking effect by more than 99 % at a loss of 5.7 % of transparency compared to neat gelatin films. The addition of curcumin (up to 1 wt%) significantly improved mechanical and water vapor barrier properties. Also, the gelatin/curcumin composite films exhibited remarkable antimicrobial activity against foodborne pathogenic bacteria, E. coli and L. monocytogenes, and showed strong antioxidant activity comparable to ascorbic acid. Antibacterial and antioxidant gelatin/curcumin composite films with improved UV protection, water vapor barrier and mechanical properties have high potential in active food packaging applications.

Bacterial cellulose films with ZnO nanoparticles and propolis extracts: Synergistic antimicrobial effect

This study aimed to obtain possible materials for future antimicrobial food packaging applications based on biodegradable bacterial cellulose (BC). BC is a fermentation product obtained by Gluconacetobacter xylinum using food or agricultural wastes as substrate. In this work we investigated the synergistic effect of zinc oxide nanoparticles (ZnO NPs) and propolis extracts deposited on BC. ZnO NPs were generated in the presence of ultrasounds directly on the surface of BC films. The BC-ZnO composites were further impregnated with ethanolic propolis extracts (EEP) with different concentrations.The composition of raw propolis and EEP were previously determined by gas-chromatography mass-spectrometry (GC-MS), while the antioxidant activity was evaluated by TEAC (Trolox equivalent antioxidant capacity). The analysis methods performed on BC-ZnO composites such as scanning electron microscopy (SEM), thermo-gravimetrically analysis (TGA), and energy-dispersive X-ray spectroscopy (EDX) proved that ZnO NPs were formed and embedded in the whole structure of BC films. The BC-ZnO-propolis films were characterized by SEM and X-ray photon spectroscopy (XPS) in order to investigate the surface modifications. The antimicrobial synergistic effect of the BC-ZnO-propolis films were evaluated against Escherichia coli, Bacillus subtilis, and Candida albicans. The experimental results revealed that BC-ZnO had no influence on Gram-negative and eukaryotic cells.

An Efficient Disinfectant, Composite Material {SLS@[Zn3(CitH)2]} as Ingredient for Development of Sterilized and Non Infectious Contact Lens

The [Zn₃(CitH)₂] (1) (CitH₄= citric acid), was dispersed in sodium lauryl sulphate (SLS) to form the micelle of SLS@[Zn₃(CitH)₂] (2). This material 2 was incorporated in hydrogel made by hydroxyethyl-methacrylate (HEMA), an ingredient of contact lenses, toward the formation of pHEMA@(SLS@[Zn₃(CitH)₂]) (3). Samples of 1 and 2 were characterized by UV-Vis, ¹H-NMR, FT-IR, FT-Raman, single crystal X-ray crystallography, X-ray fluorescence analysis, atomic absorption and TG/DTA/DSC. The antibacterial activity of 1–3 as well as of SLS against Gram-positive (Staphylococcus epidermidis (St. epidermidis) and Staphylococcus aureus (St. aureus)) and Gram-negative (Pseudomonas aeruginosa (PAO1), and Escherichia coli (E. coli)) bacteria was evaluated by the means of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and inhibitory zone (IZ). 2 showed 10 to 20-fold higher activity than 1 against the bacteria tested. Moreover the 3 decreases the abundance of Gram-positive microbes up to 30% (St. aureus) and up to 20% (PAO1) the Gram-negative ones. The noteworthy antimicrobial activity of the obtained composite 3 suggests an effective antimicrobial additive for infection-free contact lenses.

Nuclear Magnetic Resonance (NMR) Spectroscopy in Food Science: A Comprehensive Review

Nuclear magnetic resonance (NMR) spectroscopy is a robust method, which can rapidly analyze mixtures at the molecular level without requiring separation and/or purification steps, making it ideal for applications in food science. Despite its increasing popularity among food scientists, NMR is still an underutilized methodology in this area, mainly due to its high cost, relatively low sensitivity, and the lack of NMR expertise by many food scientists. The aim of this review is to help bridge the knowledge gap that may exist when attempting to apply NMR methodologies to the field of food science. We begin by covering the basic principles required to apply NMR to the study of foods and nutrients. A description of the discipline of chemometrics is provided, as the combination of NMR with multivariate statistical analysis is a powerful approach for addressing modern challenges in food science. Furthermore, a comprehensive overview of recent and key applications in the areas of compositional analysis, food authentication, quality control, and human nutrition is provided. In addition to standard NMR techniques, more sophisticated NMR applications are also presented, although limitations, gaps, and potentials are discussed. We hope this review will help scientists gain some of the knowledge required to apply the powerful methodology of NMR to the rich and diverse field of food science.