A Low-Molecular-Weight Alginate Oligosaccharide Disrupts Pseudomonal Microcolony Formation and Enhances Antibiotic Effectiveness

Enzyme-Linked Lipid Nanocarriers for Coping Pseudomonal Pulmonary Infection. Would Nanocarriers Complement Biofilm Disruption or Pave Its Road?

Introduction

Cystic fibrosis (CF) is associated with pulmonary Pseudomonas aeruginosa infections persistent to antibiotics.

Methods

To eradicate pseudomonal biofilms, solid lipid nanoparticles (SLNs) loaded with quorum-sensing-inhibitor (QSI, disrupting bacterial crosstalk), coated with chitosan (CS, improving internalization) and immobilized with alginate lyase (AL, destroying alginate biofilms) were developed.

Results

SLNs (140-205 nm) showed prolonged release of QSI with no sign of acute toxicity to A549 and Calu-3 cells. The CS coating improved uptake, whereas immobilized-AL ensured >1.5-fold higher uptake and doubled SLN diffusion across the artificial biofilm sputum model. Respirable microparticles comprising SLNs in carbohydrate matrix elicited aerodynamic diameters MMAD (3.54, 2.48 µm) and fine-particle-fraction FPF (65, 48%) for anionic and cationic SLNs, respectively. The antimicrobial and/or antibiofilm activity of SLNs was explored in Pseudomonas aeruginosa reference mucoid/nonmucoid strains as well as clinical isolates. The full growth inhibition of planktonic bacteria was dependent on SLN type, concentration, growth medium, and strain. OD measurements and live/dead staining proved that anionic SLNs efficiently ceased biofilm formation and eradicated established biofilms, whereas cationic SLNs unexpectedly promoted biofilm progression. AL immobilization increased biofilm vulnerability; instead, CS coating increased biofilm formation confirmed by 3D-time lapse confocal imaging. Incubation of SLNs with mature biofilms of P. aeruginosa isolates increased biofilm density by an average of 1.5-fold. CLSM further confirmed the binding and uptake of the labeled SLNs in P. aeruginosa biofilms. Considerable uptake of CS-coated SLNs in non-mucoid strains could be observed presumably due to interaction of chitosan with LPS glycolipids in the outer cell membrane of P. aeruginosa.

Conclusion

The biofilm-destructive potential of QSI/SLNs/AL inhalation is promising for site-specific biofilm-targeted interventional CF therapy. Nevertheless, the intrinsic/extrinsic fundamentals of nanocarrier-biofilm interactions require further investigation.

Co-spray dried inhalable composite powders of ciprofloxacin and alginate oligosaccharide as anti-biofilm therapy

The treatment of chronic respiratory infections caused by biofilm formation are extremely challenging owing to poor drug penetration into the complex biofilm structure and high drug resistance. Local delivery of an antibiotic together with a non-antibiotic adjuvant to the lungs could often enhance the therapeutic responses by targeting different bacterial growth pathways and minimizing drug resistance. In this study, we designed new inhalable dry powders containing ciprofloxacin (CIP) and OligoG (Oli, a low-molecular-weight alginate oligosaccharide impairing the mucoid biofilms by interacting with their cationic ions) to combat respiratory bacterial biofilm infections. The resulting powders were characterized with respect to their morphology, solid-state property, surface chemistry, moisture sorption behavior, and dissolution rate. The aerosol performance and storage stability of the dry powders were also evaluated. The results showed that inhalable dry powders composed of CIP and Oli could be readily accomplished via the wet milling and spray drying process. Upon the storage under 20 ± 2 °C/20 ± 2 % relative humidity (RH) for one month, there was no significant change in the in vitro aerosol performances of the dry powders. In contrast, the dry powders became non-inhalable following the storage at 20 ± 2 °C/53 ± 2 % RH for one month due to the hygroscopic nature of Oli, which could be largely prevented by incorporation of leucine. Collectively, this study suggests that the newly developed co-spray-dried powders composed of CIP and Oli might represent a promising and alternative treatment strategy against respiratory bacterial biofilm infections.

The use of combination therapy for the improvement of colistin activity against bacterial biofilm

Colistin is used as a last resort for the management of infections caused by multi-drug resistant (MDR) bacteria. However, the use of this antibiotic could lead to different side effects, such as nephrotoxicity, in most patients, and the high prevalence of colistin-resistant strains restricts the use of colistin in the clinical setting. Additionally, colistin could induce resistance through the increased formation of biofilm; biofilm-embedded cells are highly resistant to antibiotics, and as with other antibiotics, colistin is impaired by bacteria in the biofilm community. In this regard, the researchers used combination therapy for the enhancement of colistin activity against bacterial biofilm, especially MDR bacteria. Different antibacterial agents, such as antimicrobial peptides, bacteriophages, natural compounds, antibiotics from different families, N-acetylcysteine, and quorum-sensing inhibitors, showed promising results when combined with colistin. Additionally, the use of different drug platforms could also boost the efficacy of this antibiotic against biofilm. The mentioned colistin-based combination therapy not only could suppress the formation of biofilm but also could destroy the established biofilm. These kinds of treatments also avoided the emergence of colistin-resistant subpopulations, reduced the required dosage of colistin for inhibition of biofilm, and finally enhanced the dosage of this antibiotic at the site of infection. However, the exact interaction of colistin with other antibacterial agents has not been elucidated yet; therefore, further studies are required to identify the precise mechanism underlying the efficient removal of biofilms by colistin-based combination therapy.

A Novel Bifunctional Alginate Lyase and Antioxidant Activity of the Enzymatic Hydrolysates

Alginate lyase Aly448, a potential new member of the polysaccharide lyase (PL) 7 family, which was cloned and identified from the macroalgae-associated bacterial metagenomic library, showed bifunctionality. The molecular docking results revealed that Aly448 has two completely different binding sites for alginate (polyMG), poly-α-l-guluronic acid (polyG), and poly-β-d-mannuronic acid (polyM) substrates, respectively, which might be the molecular basis for the enzyme's bifunctionality. Truncational results confirmed that predicted key residues affected the bifunctionality of Aly448, but did not wholly explain. Besides, Aly448 presented excellent biochemical characteristics, such as higher thermal stability and pH tolerance. Degradation of polyMG, polyM, and polyG substrates by Aly448 produced tetrasaccharide (DP4), disaccharide (DP2), and galactose (DP1), which exhibited excellent antioxidant activity. These findings provide novel insights into the substrate recognition mechanism of bifunctional alginate lyases and pave a new path for the exploitation of natural antioxidant agents.

Elicitor Activity of Low-Molecular-Weight Alginates Obtained by Oxidative Degradation of Alginates Extracted from Sargassum muticum and Cystoseira myriophylloides

Alginates extracted from two Moroccan brown seaweeds and their derivatives were investigated for their ability to induce phenolic metabolism in the roots and leaves of tomato seedlings. Sodium alginates (ALSM and ALCM) were extracted from the brown seaweeds Sargassum muticum and Cystoseira myriophylloides, respectively. Low-molecular-weight alginates (OASM and OACM) were obtained after radical hydrolysis of the native alginates. Elicitation was carried out by foliar spraying 20 mL of aqueous solutions (1 g/L) on 45-day-old tomato seedlings. Elicitor capacities were evaluated by monitoring phenylalanine ammonia-lyase (PAL) activity, polyphenols, and lignin production in the roots and leaves after 0, 12, 24, 48, and 72 h of treatment. The molecular weights (Mw) of the different fractions were 202 kDa for ALSM, 76 kDa for ALCM, 19 kDa for OACM, and 3 kDa for OASM. FTIR analysis revealed that the structures of OACM and OASM did not change after oxidative degradation of the native alginates. These molecules showed their differential capacity to induce natural defenses in tomato seedlings by increasing PAL activity and through the accumulation of polyphenol and lignin content in the leaves and roots. The oxidative alginates (OASM and OACM) exhibited an effective induction of the key enzyme of phenolic metabolism (PAL) compared to the alginate polymers (ALSM and ALCM). These results suggest that low-molecular-weight alginates may be good candidates for stimulating the natural defenses of plants.

How Three Self-Secreted Biofilm Exopolysaccharides of Pseudomonas aeruginosa, Psl, Pel, and Alginate, Can Each Be Exploited for Antibiotic Adjuvant Effects in Cystic Fibrosis Lung Infection

In cystic fibrosis (CF), pulmonary infection with Pseudomonas aeruginosa is a cause of increased morbidity and mortality, especially in patients for whom infection becomes chronic and there is reliance on long-term suppressive therapies. Current antimicrobials, though varied mechanistically and by mode of delivery, are inadequate not only due to their failure to eradicate infection but also because they do not halt the progression of lung function decline over time. One of the reasons for this failure is thought to be the biofilm mode of growth of P. aeruginosa, wherein self-secreted exopolysaccharides (EPSs) provide physical protection against antibiotics and an array of niches with resulting metabolic and phenotypic heterogeneity. The three biofilm-associated EPSs secreted by P. aeruginosa (alginate, Psl, and Pel) are each under investigation and are being exploited in ways that potentiate antibiotics. In this review, we describe the development and structure of P. aeruginosa biofilms before examining each EPS as a potential therapeutic target for combating pulmonary infection with P. aeruginosa in CF, with a particular focus on the current evidence for these emerging therapies and barriers to bringing these therapies into clinic.

Gut-Spleen Axis: Microbiota via Vascular and Immune Pathways Improve Busulfan-Induced Spleen Disruption

Fecal microbiota transplantation (FMT) is an effective means of modulating gut microbiota for the treatment of many diseases, including Clostridioides difficile infections. The gut-spleen axis has been established, and this is involved in the development and function of the spleen. However, it is not understood whether gut microbiota can be used to improve spleen function, especially in spleens disrupted by a disease or an anti-cancer treatment. In the current investigation, we established that alginate oligosaccharide (AOS)-improved gut microbiota (A10-FMT) can rescue anticancer drug busulfan-disrupted spleen vasculature and spleen function. A10-FMT improved the gene and/or protein expression of genes involved in vasculature development, increased the cell proliferation rate, enhanced the endothelial progenitor cell capability, and elevated the expression of the cell junction molecules to increase the vascularization of the spleen. This investigation found for the first time that the reestablishment of spleen vascularization restored spleen function by improving spleen immune cells and iron metabolism. These findings may be used as a strategy to minimize the side effects of anti-cancer drugs or to improve spleen vasculature-related diseases. IMPORTANCE Alginate oligosaccharide (AOS)-improved gut microbiota (A10-FMT) can rescue busulfan disrupted spleen vasculature. A10-FMT improved the cell proliferation rate, endothelial progenitor cell capability, and cell junction molecules to increase vasculature formation in the spleen. This reestablishment restored spleen function by improving spleen immune cells and iron metabolism. These findings are useful for the treatment of spleen vasculature-related diseases.

Alginate Oligosaccharides Repair Liver Injury by Improving Anti-Inflammatory Capacity in a Busulfan-Induced Mouse Model

Liver diseases are associated with many factors, including medicines and alcoholics, which have become a global problem. It is crucial to overcome this problem. Liver diseases always come with inflammatory complications, which might be a potential target to deal with this issue. Alginate oligosaccharides (AOS) have been demonstrated to have many beneficial effects, especially anti-inflammation. In this study, 40 mg/kg body weight (BW) of busulfan was intraperitoneally injected once, and then the mice were dosed with ddH₂O or AOS 10 mg/kg BW every day by oral gavage for five weeks. We investigated AOS as a potential no-side-effect and low-cost therapy for liver diseases. For the first time, we discovered that AOS 10 mg/kg recovered liver injury by decreasing the inflammation-related factors. Moreover, AOS 10 mg/kg could improve the blood metabolites related to immune and anti-tumor effects, and thus, ameliorated impaired liver function. The results indicate that AOS may be a potential therapy to deal with liver damage, especially in inflammatory conditions.

Cloning, Expression and Characterization of an Alginate Lyase in Bacillus subtilis WB600

The aim of this study was to further broaden the heterologous expression of alginate lyase from Vibrio alginolyticus in a Bacillus subtilis expression vector. A B. subtilis WB600/pP43NMK-alg62 strain was constructed. (NH4)2SO4 precipitation and Ni-affinity chromatography were performed to purify the enzyme. We then characterized the enzyme. Its molecular weight was 57.64 kDa, and it worked optimally at 30 °C with a pH of 8.0. Ca2+ markedly enhanced the enzymatic activity of Alg62 while Cu2+ and Ni2+ inhibited its activity. Alg62 had a wide range of substrate specificity, showing high activity toward sodium alginate and polyG. Following optimization of the fermentation process, the optimal conditions for the recombinant expression of Alg62 were as follows: temperature of 37 °C, pH of 7.0, medium consisting of glycerol 15 g/L, yeast powder 25 g/L and K+ 1.5 mmol/L. At these optimal conditions, enzyme activity reached 318.21 U/mL, which was 1.54 times higher than the initial enzyme activity.

Process and applications of alginate oligosaccharides with emphasis on health beneficial perspectives

Alginates are linear polymers comprising 40% of the dry weight of algae possess various applications in food and biomedical industries. Alginate oligosaccharides (AOS), a degradation product of alginate, is now gaining much attention for their beneficial role in food, pharmaceutical and agricultural industries. Hence this review was aimed to compile the information on alginate and AOS (prepared from seaweeds) during 1994-2020. As per our knowledge, this is the first review on the potential use of alginate oligosaccharides in different fields. The alginate derivatives are grouped according to their applications. They are involved in the isolation process and show antimicrobial, antioxidant, anti-inflammatory, antihypertension, anticancer, and immunostimulatory properties. AOS also have significant applications in prebiotics, nutritional supplements, plant growth development and others products.

The Spray-Dried Alginate/Gelatin Microparticles with Luliconazole as Mucoadhesive Drug Delivery System

Candida species are opportunistic fungi, which are primary causative agents of vulvovaginal candidiasis. The cure of candidiasis is difficult, lengthy, and associated with the fungi resistivity. Therefore, the research for novel active substances and unconventional drug delivery systems providing effective and safe treatment is still an active subject. Microparticles, as multicompartment dosage forms due to larger areas, provide short passage of drug diffusion, which might improve drug therapeutic efficiency. Sodium alginate is a natural polymer from a polysaccharide group, possessing swelling, mucoadhesive, and gelling properties. Gelatin A is a natural high-molecular-weight polypeptide obtained from porcine collagen. The purpose of this study was to prepare microparticles by the spray-drying of alginate/gelatin polyelectrolyte complex mixture, with a novel antifungal drug-luliconazole. In the next stage of research, the effect of gelatin presence on pharmaceutical properties of designed formulations was assessed. Interrelations among polymers were evaluated with thermal analysis and Fourier transform infrared spectroscopy. A valid aspect of this research was the in vitro antifungal activity estimation of designed microparticles using Candida species: C. albicans, C. krusei, and C. parapsilosis. It was shown that the gelatin addition affected the particles size, improved encapsulation efficiency and mucoadhesiveness, and prolonged the drug release. Moreover, gelatin addition to the formulations improved the antifungal effect against Candida species.

Polyguluronate simulations shed light onto the therapeutic action of OligoG CF-5/20

Chronic mucoid P. aeruginosa cystic fibrosis (CF) lung infections are associated with the development of a biofilm composed of anionic acetylated exopolysaccharide (EPS) alginate, electrostatically stabilised by extracellular Ca2+ ions. OligoG CF-5/20, a low molecular weight guluronate rich oligomer, is emerging as a novel therapeutic capable of disrupting mature P. aeruginosa biofilms. However, its method of therapeutic action on the mucoid biofilm EPS is not definitively known at a molecular level. This work, utilising molecular dynamics (MD) and Density-Functional Theory (DFT), has revealed that OligoG CF-5/20 interaction with the EPS is facilitated solely through bridging Ca2+ ions, which are not liberated from their native EPS binding sites upon OligoG CF-5/20 dispersal, suggesting that OligoG CF-5/20 does not cause disruptions to mature P. aeruginosa biofilms through breaking EPS-Ca2+-EPS ionic cross-links. Rather it is likely that the therapeutic activity arises from sequestering free Ca2+ ions and preventing further Ca2+ induced EPS aggregation.

Alginate oligosaccharides increase boar semen quality by affecting gut microbiota and metabolites in blood and sperm

Alginate oligosaccharides (AOS), natural polymers from brown seaweeds (such as Laminaria japonica, Undaria pinnatifida, and Sargassum fusiforme), have been reported to possess many beneficial advantages for health. In the current study, after 9 weeks of dietary supplementation, AOS 10 mg/kg group (AOS 10) group increased boar sperm motility from 87.8% to 93.5%, p < 0.05. Moreover, AOS10 increased the relative abundances of Bifidobacterium, Coprococcus, Butyricicoccus (1.3–2.3-fold; p < 0.05) to increase the beneficial blood and sperm metabolites (1.2–1.6-fold; p < 0.05), and important sperm proteins such as gelsolin, Zn-alpha2 glycoprotein, Cation Channel Sperm-Associated Protein, outer dense fiber of sperm tails, etc. (1.5–2.2-fold; p < 0.05). AOS had a long-term beneficial advantage on boar semen quality by the increase in semen volume (175 vs. 160 ml/ejaculation, p < 0.05). AOS may be used as dietary additives for improving semen quality.

A bifunctional exolytic alginate lyase from Microbulbifer sp. ALW1 with salt activation and calcium-dependent catalysis

Alginate lyases can depolymerize alginate to oligomers with potential applications in many fields. Here a new alginate lyase, namely AlgL6, was characterized from Microbulbifer sp. ALW1, phylogenetically classified into the polysaccharide lyase family 6 (PL6). The recombinant alginate lyase AlgL6 exerted enzymatic activities towards polymannuronate, polyguluronate, and sodium alginate in an exolytic manner. AlgL6 had an optimum temperature of 35 °C and good stability at 30 °C or below. Its optimum pH was 8.0, and it had good stability over the pH range of 5.0-9.0. AlgL6 exhibited excellent halo-stability against Na⁺, and its activity can be increased up to about 1.8 times by 0.5 M NaCl. AlgL6 also showed strong stability in the presence of some nonionic detergents such as Tween 20 and Tween 80. The degradation products of sodium alginate by AlgL6 exhibited more effective antioxidant activities than the undigested polysaccharides. Structure analysis illustrated the catalytic mechanism defined by the coordination of the acid/base residues Arg269 and Lys248 of AlgL6. The replacement of Ca²⁺-interacting amino acid residues in AlgL6 and depletion of Ca²⁺ suggested the involvement of Ca²⁺ in the enzyme's catalytic activity. These properties of AlgL6 supply support to its industrial application for development of alginate bioresource.

Alginate Oligosaccharides Ameliorate DSS-Induced Colitis through Modulation of AMPK/NF-κB Pathway and Intestinal Microbiota

Alginate oligosaccharides (AOS) are shown to have various biological activities of great value to medicine, food, and agriculture. However, little information is available about their beneficial effects and mechanisms on ulcerative colitis. In this study, AOS with a polymerization degree between 2 and 4 were found to possess anti-inflammatory effects in vitro and in vivo. AOS could decrease the levels of nitric oxide (NO), IL-1β, IL-6, and TNFα, and upregulate the levels of IL-10 in both RAW 264.7 and bone-marrow-derived macrophage (BMDM) cells under lipopolysaccharide (LPS) stimulation. Additionally, oral AOS administration could significantly prevent bodyweight loss, colonic shortening, and rectal bleeding in dextran sodium sulfate (DSS)-induced colitis mice. AOS pretreatment could also reduce disease activity index scores and histopathologic scores and downregulate proinflammatory cytokine levels. Importantly, AOS administration could reverse DSS-induced AMPK deactivation and NF-κB activation in colonic tissues, as evidenced by enhanced AMPK phosphorylation and p65 phosphorylation inhibition. AOS could also upregulate AMPK phosphorylation and inhibit NF-κB activation in vitro. Moreover, 16S rRNA gene sequencing of gut microbiota indicated that supplemental doses of AOS could affect overall gut microbiota structure to a varying extent and specifically change the abundance of some bacteria. Medium-dose AOS could be superior to low- or high-dose AOS in maintaining remission in DSS-induced colitis mice. In conclusion, AOS can play a protective role in colitis through modulation of gut microbiota and the AMPK/NF-kB pathway.

Does the Freeze-Thaw Technique Affect the Properties of the Alginate/Chitosan Glutamate Gels with Posaconazole as a Model Antifungal Drug?

Hydrogels are semi-solid systems with high flexibility, which, due to holding large amounts of water, are similar to natural tissues and are very useful in the field of biomedical applications. Despite the wide range of polymers available to form hydrogels, novel techniques utilized to obtain hydrogels with adequate properties are still being developed. The aim of this study was to evaluate the impact of the freeze–thaw technique on the properties of cryogels based on sodium alginate and chitosan glutamate with posaconazole as a model antifungal substance. The effect of the freezing and thawing process on the physicochemical, rheological, textural and bioadhesive properties of prepared cryogels was examined. Additionally, the antifungal activity against Candida albicans, Candida parapsilosis and Candida krusei of designed formulations was examined. It was shown that the freeze–thaw technique significantly improved viscosity, bioadhesiveness, textural properties and prolonged the in vitro posaconazole release. Moreover, alginate/chitosan glutamate cryogels exhibited higher values of inhibition zone in C. parapsilosis culture than traditional hydrogel formulations.

The role of functional oligosaccharides as prebiotics in ulcerative colitis

The incidence rate of ulcerative colitis (UC) has increased significantly over the past decades and it places an increasing burden on health and social systems. The current studies on UC implicate a strong correlation between host gut microbiota immunity and the pathogenesis of UC. Meanwhile, more and more functional oligosaccharides have been reported as prebiotics to alleviate UC, since many of them can be metabolized by gut microbiota to produce short-chain fatty acids (SCFAs). The present review is focused on the structure, sources and specific applications of various functional oligosaccharides related to the prevention and treatment of UC. The available evidence for the usage of functional oligosaccharides in UC treatment are summarized, including fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), chito-oligosaccharides (COS), alginate-oligosaccharides (AOS), xylooligosaccharides (XOS), stachyose and inulin.

Enhancing Colistin Activity against Colistin-Resistant Escherichia coli through Combination with Alginate Nanoparticles and Small Molecules

Bacterial resistance to antibiotics has become a major public health problem worldwide, with the yearly number of deaths exceeding 700,000. To face this well-acknowledged threat, new molecules and therapeutic methods are considered. In this context, the application of nanotechnology to fight bacterial infection represents a viable approach and has experienced tremendous developments in the last decades. Escherichia coli (E. coli) is responsible for severe diarrhea, notably in the breeding sector, and especially in pig farming. The resulting infection (named colibacillosis) occurs in young piglets and could lead to important economic losses. Here, we report the design of several new formulations based on colistin loaded on alginate nanoparticles (Alg NPs) in the absence, but also in the presence, of small molecules, such as components of essential oils, polyamines, and lactic acid. These new formulations, which are made by concomitantly binding colistin and small molecules to Alg NPs, were successfully tested against E. coli 184, a strain resistant to colistin. When colistin was associated with Alg NPs, the minimal inhibition concentration (MIC) decreased from 8 to 1 µg/mL. It is notable that when menthol or lactic acid was co-loaded with colistin on Alg NPs, the MIC of colistin drastically decreased, reaching 0.31 or 0.62 µg/mL, respectively. These novel bactericidal formulations, whose innocuity towards eukaryotic HT-29 cells was established in vitro, are presumed to permeabilize the bacterial membrane and provoke the leakage of intracellular proteins. Our findings revealed the potentiating effect of the Alg NPs on colistin, but also of the small molecules mentioned above. Such ecological and economical formulations are easy to produce and could be proposed, after confirmation by in vivo and toxicology tests, as therapeutic strategies to replace fading antibiotics.

Preparation and potential applications of alginate oligosaccharides

Alginate, a linear polymer consisting of β-D-mannuronic acid (M) and α-L-guluronic acid (G) with 1,4-glycosidic linkages and comprising 40% of the dry weight of algae, possesses various applications in the food and nutraceutical industries. However, the potential applications of alginate are restricted in some fields because of its low water solubility and high solution viscosity. Alginate oligosaccharides (AOS) on the other hand, have low molecular weight which result in better water solubility. Hence, it becomes a more popular target to be researched in recent years for its use in foods and nutraceuticals. AOS can be obtained by multiple degradation methods, including enzymatic degradation, from alginate or alginate-derived poly G and poly M. AOS have unique bioactivity and can bring human health benefits, which render them potentials to be developed/incorporated into functional food. This review comprehensively covers methods of the preparation and analysis of AOS, and discussed the potential applications of AOS in foods and nutraceuticals.

Alginate oligosaccharides enhance diffusion and activity of colistin in a mucin-rich environment

In a number of chronic respiratory diseases e.g. cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD), the production of viscous mucin reduces pulmonary function and represents an effective barrier to diffusion of inhaled therapies e.g. antibiotics. Here, a 2-compartment Transwell model was developed to study impaired diffusion of the antibiotic colistin across an artificial sputum (AS) matrix/medium and to quantify its antimicrobial activity against Pseudomonas aeruginosa NH57388A biofilms (alone and in combination with mucolytic therapy). High-performance liquid chromatography coupled with fluorescence detection (HPLC-FLD) revealed that the presence of AS medium significantly reduced the rate of colistin diffusion (> 85% at 48 h; p < 0.05). Addition of alginate oligosaccharide (OligoG CF-5/20) significantly improved colistin diffusion by 3.7 times through mucin-rich AS medium (at 48 h; p < 0.05). Increased diffusion of colistin with OligoG CF-5/20 was shown (using confocal laser scanning microscopy and COMSTAT image analysis) to be associated with significantly increased bacterial killing (p < 0.05). These data support the use of this model to study drug and small molecule delivery across clinically-relevant diffusion barriers. The findings indicate the significant loss of colistin and reduced effectiveness that occurs with mucin binding, and support the use of mucolytics to improve antimicrobial efficacy and lower antibiotic exposure.

Alginate oligosaccharides protect against fumonisin B1-induced intestinal damage via promoting gut microbiota homeostasis

Fumonisin B1 (FB1), one of the most common mycotoxins contaminating feed and food, has been shown to induce intestinal barrier degradation. However, its role on gut microbiota in this process is still unclear. Alginate oligosaccharides (AOS) have been reported to exert their anti-inflammatory and anti-apoptotic function partially via modulation the gut microbiota. However, little is known about the beneficial effect of AOS on gut microbiota upon FB1 exposure. Results show that FB1 degraded intestinal epithelial barrier function as evidenced by increased pathological epithelial cell shedding, reduced the number of goblet cells, and promoted intestinal cell apoptosis. Markedly, FB1 disturbed the cecal and fecal microbiota composition. FB1 increased the level of Lactobacillus and decreased the relative abundance of beneficial microbes. FB1 largely inhibited the production of short chain fatty acids (SCFAs). AOS greatly ameliorated FB1-induced intestinal damage, inflammation, and oxidative stress (eg., T-SOD and MDA). AOS alleviated gut microbial dysbiosis by promoting the growth of beneficial microbes such as Roseburia, Bifidobacterium, and Akkermansia, and increasing SCFAs production upon FB1 exposure. Moreover, the correlation analysis showed that FB1- and AOS-treated gut microbiota alteration is closely associated with the change of intestinal phenotype. We have thus provided a novel insight into the protective role of AOS on FB1-induced gut microbial dysbiosis.

Combination and nanotechnology based pharmaceutical strategies for combating respiratory bacterial biofilm infections

Respiratory infections are one of the major global health problems. Among them, chronic respiratory infections caused by biofilm formation are difficult to treat because of both drug tolerance and poor drug penetration into the complex biofilm structure. A major part of the current research on combating respiratory biofilm infections have been focused on destroying the matrix of extracellular polymeric substance and eDNA of the biofilm or promoting the penetration of antibiotics through the extracellular polymeric substance via delivery technologies in order to kill the bacteria inside. There are also experimental data showing that certain inhaled antibiotics with simple formulations can effectively penetrate EPS to kill surficially located bacteria and centrally located dormant bacteria or persisters. This article aims to review recent advances in the pharmaceutical strategies for combating respiratory biofilm infections with a focus on nanotechnology-based drug delivery approaches. The formation and characteristics of bacterial biofilm infections in the airway mucus are presented, which is followed by a brief review on the current clinical approaches to treat respiratory biofilm infections by surgical removal and antimicrobial therapy, and also the emerging clinical treatment approaches. The current combination of antibiotics and non-antibiotic adjuvants to combat respiratory biofilm infections are also discussed.

Brown Algae Carbohydrates: Structures, Pharmaceutical Properties, and Research Challenges

Brown algae (Phaeophyceae) have been consumed by humans for hundreds of years. Current studies have shown that brown algae are rich sources of bioactive compounds with excellent nutritional value, and are considered functional foods with health benefits. Polysaccharides are the main constituents of brown algae; their diverse structures allow many unique physical and chemical properties that help to moderate a wide range of biological activities, including immunomodulation, antibacterial, antioxidant, prebiotic, antihypertensive, antidiabetic, antitumor, and anticoagulant activities. In this review, we focus on the major polysaccharide components in brown algae: the alginate, laminarin, and fucoidan. We explore how their structure leads to their health benefits, and their application prospects in functional foods and pharmaceuticals. Finally, we summarize the latest developments in applied research on brown algae polysaccharides.

Secretory Expression of an Alkaline Alginate Lyase With Heat Recovery Property in Yarrowia lipolytica

Alginate lyase possesses wide application prospects for the degradation of brown algae and preparation of alginate oligosaccharides, and its degradation products display a variety of biological activities. Although many enzymes of this type have been reported, alginate lyases with unique properties are still relatively rare. In the present work, an alginate lyase abbreviated as Alyw203 has been cloned from Vibrio sp. W2 and expressed in food-grade Yarrowia lipolytica. The Alyw203 gene consists of an open reading frame (ORF) of 1,566 bp containing 521 amino acids, of which the first 17 amino acids are considered signal peptides, corresponding to secretory features. The peak activity of the current enzyme appears at 45°C with a molecular weight of approximately 57.0 kDa. Interestingly, Alyw203 exhibits unique heat recovery performance, returning above 90% of its initial activity in the subsequent incubation for 20 min at 10°C, which is conducive to the recovery of current enzymes at low-temperature conditions. Meanwhile, the highest activity is obtained under alkaline conditions of pH 10.0, showing outstanding pH stability. Additionally, as an alginate lyase independent of NaCl and resistant to metal ions, Alyw203 is highly active in various ionic environments. Moreover, the hydrolyzates of present enzymes are mainly concentrated in the oligosaccharides of DP1–DP2, displaying perfect product specificity. The alkali suitability, heat recovery performance, and high oligosaccharide yield of Alyw203 make it a potential candidate for industrial production of the monosaccharide and disaccharide.

Potential applications of alginate oligosaccharides for biomedicine - A mini review

Extensive research on marine algae, especially on their health-promoting properties, has been conducted. Various ingredients with potential biomedical applications have been discovered and extracted from marine algae. Alginate oligosaccharides are low molecular weight alginate polysaccharides present in cell walls of brown algae. They exhibit various health benefits such as anti-inflammatory, anti-microbial, anti-oxidant, anti-tumor and immunomodulation. Their low-toxicity, non-immunogenicity, and biodegradability make them an excellent material in biomedicine. Alginate oligosaccharides can be chemically or biochemically modified to enhance their biological activity and potential in pharmaceutical applications. This paper provides a brief overview on alginate oligosaccharides characteristics, modification patterns and highlights their vital health promoting properties.

Alginate oligosaccharide protects against enterotoxigenic Escherichia coli-induced porcine intestinal barrier injury

Alginate oligosaccharide (AOS) possesses various pharmaceutical benefits, making it an attractive candidate for biomedical applications. In the present study, we prepared AOS by depolymerising alginate; its degree of polymerisation mainly ranged from 2 to 8. We confirmed the enteroprotective potential of AOS against enterotoxigenic Escherichia coli (ETEC)-induced intestinal barrier injury in weaned pigs. Next, we illustrated the mechanisms underlying this effect of AOS using the porcine small intestinal epithelial cell line IPEC-J2. AOS potently reduced the binding of the bacteria-deprived endotoxin lipopolysaccharide (LPS) to the IPEC-J2 cell surface. Moreover, it suppressed the LPS-induced production of pro-inflammatory cytokines and the nuclear translocation of nuclear factor-κB (NF-κB) p65 in IPEC-J2 cells. These results indicate that AOS protects the intestinal epithelium from ETEC-induced inflammatory injury by preventing the activation of NF-κB, implying that AOS could be used as an anti-inflammatory agent for treating inflammation-related intestinal diseases in mammals.

Alginate derived functional oligosaccharides: Recent developments, barriers, and future outlooks

Alginate is a biopolymer used extensively in the food, pharmaceutical, and chemical industries. Alginate oligosaccharides (AOS) derived from alginate exhibit superior biological activities and therapeutic potential. Alginate lyases with characteristic substrate specificity can facilitate the production of a broad array of AOS with precise structure and functionality. By adopting innovative analytical tools in conjunction with focused clinical studies, the structure-bioactivity relationship of a number of AOS has been brought to light. This review covers fundamental aspects and recent developments in AOS research. Enzymatic and microbial processes involved in AOS production from brown algae and sequential steps involved in AOS structure elucidation are outlined. Biological mechanisms underlying the health benefits of AOS and their potential industrial and therapeutic applications are elaborated. Withal, various challenges in AOS research are traced out, and future directions, specifically on recombinant systems for AOS preparation, are delineated to further widen the horizon of these exceptional oligosaccharides.

Quantifying the effects of antibiotic treatment on the extracellular polymer network of antimicrobial resistant and sensitive biofilms using multiple particle tracking

Novel therapeutics designed to target the polymeric matrix of biofilms requires innovative techniques to accurately assess their efficacy. Here, multiple particle tracking (MPT) was developed to characterize the physical and mechanical properties of antimicrobial resistant (AMR) bacterial biofilms and to quantify the effects of antibiotic treatment. Studies employed nanoparticles (NPs) of varying charge and size (40-500 nm) in Pseudomonas aeruginosa PAO1 and methicillin-resistant Staphylococcus aureus (MRSA) biofilms and also in polymyxin B (PMB) treated Escherichia coli biofilms of PMB-sensitive (PMBSens) IR57 and PMB-resistant (PMBR) PN47 strains. NP size-dependent and strain-related differences in the diffusion coefficient values of biofilms were evident between PAO1 and MRSA. Dose-dependent treatment effects induced by PMB in PMBSens E. coli biofilms included increases in diffusion and creep compliance (P < 0.05), not evident in PMB treatment of PMBR E. coli biofilms. Our results highlight the ability of MPT to quantify the diffusion and mechanical effects of antibiotic therapies within the AMR biofilm matrix, offering a valuable tool for the pre-clinical screening of anti-biofilm therapies.

Enzymes and biopolymers. The opportunity for the smart design of molecular delivery systems

Enzymes exhibit a tremendous potential due to the catalytic activity in response to physiological conditions and specific microenvironments. Exploiting these properties in combination with the versatility of biopolymers, a fascinating field for the rational development of a new class of "smart" delivery systems for therapeutic molecules is proposed. Many strategies have been recently developed to produce matrices with the desirable properties of molecular release, and enzymes could be playing a relevant role in modify the chemical composition of the polymers, the porosity and surface area of the matrices and modulate the kinetic of controlled release. Enzyme based computational systems have appeared as a relevant complementary tool to design novel smart bioactive matrices for programmable drug delivery. The present review is reporting the recent advances and projections of smart biopolymeric matrices activated by enzymes for sustained release of therapeutic molecules, highlighting various applications in the area of advanced drug delivery.

Phenotypic and Genotypic Adaptations in Pseudomonas aeruginosa Biofilms following Long-Term Exposure to an Alginate Oligomer Therapy

Chronic Pseudomonas aeruginosa lung infections in cystic fibrosis (CF) evolve to generate environmentally adapted biofilm communities, leading to increased patient morbidity and mortality. OligoG CF-5/20, a low-molecular-weight inhaled alginate oligomer therapy, is currently in phase IIb/III clinical trials in CF patients. Experimental evolution of P. aeruginosa in response to OligoG CF-5/20 was assessed using a bead biofilm model allowing continuous passage (45 days; ∼245 generations). Mutants isolated after OligoG CF-5/20 treatment typically had a reduced biofilm-forming ability and altered motility profile. Genotypically, OligoG CF-5/20 provided no selective pressure on genomic mutations within morphotypes. Chronic exposure to azithromycin, a commonly prescribed antibiotic in CF patients, with or without OligoG CF-5/20 in the biofilm evolution model also had no effect on rates of resistance acquisition. Interestingly, however, cross-resistance to other antibiotics (e.g., aztreonam) was reduced in the presence of OligoG CF-5/20. Collectively, these findings show no apparent adverse effects from long-term exposure to OligoG CF-5/20, instead resulting in both fewer colonies with multidrug resistance (MDR)-associated phenotypes and improved antibiotic susceptibility of P. aeruginosa IMPORTANCE The emergence of multidrug-resistant (MDR) pathogens within biofilms in the cystic fibrosis lung results in increased morbidity. An inhalation therapy derived from alginate, OligoG CF-5/20, is currently in clinical trials for cystic fibrosis patients. OligoG CF-5/20 has been shown to alter sputum viscoelasticity, disrupt mucin polymer networks, and disrupt MDR pseudomonal biofilms. Long-term exposure to inhaled therapeutics may induce selective evolutionary pressures on bacteria within the lung biofilm. Here, a bead biofilm model with repeated exposure of P. aeruginosa to OligoG CF-5/20 (alone and in combination with azithromycin) was conducted to study these long-term effects and characterize the phenotypic and genotypic adaptations which result. These findings, over 6 weeks, show that long-term use of OligoG CF-5/20 does not lead to extensive mutational changes and may potentially decrease the pathogenicity of the bacterial biofilm and improve the susceptibility of P. aeruginosa to other classes of antibiotics.

Implementation of microbiota analysis in clinical trials for cystic fibrosis lung infection: Experience from the OligoG phase 2b clinical trials

Culture-independent microbiota analysis is widely used in research and being increasingly used in translational studies. However, methods for standardisation and application of these analyses in clinical trials are limited. Here we report the microbiota analysis that accompanied two phase 2b clinical trials of the novel, non-antibiotic therapy OligoG CF-5/20 for cystic fibrosis (CF) lung infection. Standardised protocols (DNA extraction, PCR, qPCR and 16S rRNA gene sequencing analysis) were developed for application to the Pseudomonas aeruginosa (NCT02157922) and Burkholderia cepacia complex (NCT02453789) clinical trials involving 45 and 13 adult trial participants, respectively. Microbiota analysis identified that paired sputum samples from an individual participant, taken within 2 h of each other, had reproducible bacterial diversity profiles. Although culture microbiology had identified patients as either colonised by P. aeruginosa or B. cepacia complex species at recruitment, microbiota analysis revealed patient lung infection communities were not always dominated by these key CF pathogens. Microbiota profiles were patient-specific and remained stable over the course of both clinical trials (6 sampling points over the course of 140 days). Within the Burkholderia trial, participants were infected with B. cenocepacia (n = 4), B. multivorans (n = 6), or an undetermined species (n = 3). Colonisation with either B. cenocepacia or B. multivorans influenced the overall bacterial community structure in sputum. Overall, we have shown that sputum microbiota in adults with CF is stable over a 2 h time-frame, suggesting collection of a single sample on a collection day is sufficient to capture the microbiota diversity. Despite the uniform pathogen culture-positivity status at recruitment, trial participants were highly heterogeneous in their lung microbiota. Understanding the microbiota profiles of individuals with CF ahead of future clinical trials would be beneficial in the context of patient stratification and trial design.

Characteristics and applications of alginate lyases: A review

Brown algae, as the main source of alginate, are a type of marine biomass with a very high output. Alginate, a polysaccharide composed of β-D-mannuronic acid (M) and α-L-guluronic acid (G), has great potential for applications in the food, cosmetic and pharmaceutical industries. Alginate lyases (Alys) can degrade alginate polymers into oligosaccharides or monosaccharides, resulting in a broad application field. Alys can be used for both the production of alginate oligosaccharides and the biorefinery of brown algae. In view of their important functions, an increasing number of Alys have been isolated and characterized. For better application, a comprehensive understanding of Alys is essential. Therefore, in this paper, we summarized recently discovered Alys, discussed their characteristics, and introduced their structural properties, degradation patterns and biological roles in alginate-degrading organisms. In addition, applications of Alys have been illustrated with examples. This paper provides a relatively comprehensive description of Alys, which is significant for Alys exploration and application.

Exploiting Mannuronan C-5 Epimerases in Commercial Alginate Production

Alginates are one of the major polysaccharide constituents of marine brown algae in commercial manufacturing. However, the content and composition of alginates differ according to the distinct parts of these macroalgae and have a direct impact on the concentration of guluronate and subsequent commercial value of the final product. The Azotobacter vinelandii mannuronan C-5 epimerases AlgE1 and AlgE4 were used to determine their potential value in tailoring the production of high guluronate low-molecular-weight alginates from two sources of high mannuronic acid alginates, the naturally occurring harvested brown algae (Ascophyllum nodosum, Durvillea potatorum, Laminaria hyperborea and Lessonia nigrescens) and a pure mannuronic acid alginate derived from fermented production of the mutant strain of Pseudomonas fluorescens NCIMB 10,525. The mannuronan C-5 epimerases used in this study increased the content of guluronate from 32% up to 81% in both the harvested seaweed and bacterial fermented alginate sources. The guluronate-rich alginate oligomers subsequently derived from these two different sources showed structural identity as determined by proton nuclear magnetic resonance (1H NMR), high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and size-exclusion chromatography with online multi-angle static laser light scattering (SEC-MALS). Functional identity was determined by minimum inhibitory concentration (MIC) assays with selected bacteria and antibiotics using the previously documented low-molecular-weight guluronate enriched alginate OligoG CF-5/20 as a comparator. The alginates produced using either source showed similar antibiotic potentiation effects to the drug candidate OligoG CF-5/20 currently in development as a mucolytic and anti-biofilm agent. These findings clearly illustrate the value of using epimerases to provide an alternative production route for novel low-molecular-weight alginates.

Bi-Functional Alginate Oligosaccharide-Polymyxin Conjugates for Improved Treatment of Multidrug-Resistant Gram-Negative Bacterial Infections

The recent emergence of resistance to colistin, an antibiotic of last resort with dose-limiting toxicity, has highlighted the need for alternative approaches to combat infection. This study aimed to generate and characterise alginate oligosaccharide (“OligoG”)–polymyxin (polymyxin B and E (colistin)) conjugates to improve the effectiveness of these antibiotics. OligoG–polymyxin conjugates (amide- or ester-linked), with molecular weights of 5200–12,800 g/mol and antibiotic loading of 6.1–12.9% w/w, were reproducibly synthesised. In vitro inflammatory cytokine production (tumour necrosis factor alpha (TNFα) ELISA) and cytotoxicity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) of colistin (2.2–9.3-fold) and polymyxin B (2.9–27.2-fold) were significantly decreased by OligoG conjugation. Antimicrobial susceptibility tests (minimum inhibitory concentration (MIC), growth curves) demonstrated similar antimicrobial efficacy of ester- and amide-linked conjugates to that of the parent antibiotic but with more sustained inhibition of bacterial growth. OligoG–polymyxin conjugates exhibited improved selectivity for Gram-negative bacteria in comparison to mammalian cells (approximately 2–4-fold). Both OligoG–colistin conjugates caused significant disruption of Pseudomonas aeruginosa biofilm formation and induced bacterial death (confocal laser scanning microscopy). When conjugates were tested in an in vitro “time-to-kill” (TTK) model using Acinetobacter baumannii, only ester-linked conjugates reduced viable bacterial counts (~2-fold) after 4 h. Bi-functional OligoG–polymyxin conjugates have potential therapeutic benefits in the treatment of multidrug-resistant (MDR) Gram-negative bacterial infections, directly reducing toxicity whilst retaining antimicrobial and antibiofilm activities.

Comparative genomics of the sequential Pseudomonas aeruginosa isolates obtained from the continuous imipenem stress evolution

Pseudomonas aeruginosa is a major opportunistic human pathogen that causes nosocomial infections, and the proportion of carbapenem resistance has recently dramatically increased in P. aeruginosa due to the overuse of them. In this study, strains G10 and G20, with minimum inhibitory concentration (MIC) of imipenem of 16 μg/ml and more than 32 μg/ml, were isolated during continuous subculture of cells exposed to stepwise increasing concentrations of imipenem, respectively. The genomes of G10 and G20 were sequenced and compared with parental strain (P. aeruginosa ATCC 27853, G0). There were 59, 59, and 58 genes involved in antibiotic resistance which were predicted in G0, G10, and G20, respectively, while 374, 366, and 363 genes involved in virulence factors were identified among these three strains. Due to the significantly different MICs of imipenem and highly similar profiles of antibiotic resistance and virulence factors related genes among three strains, the specific genetic variations that occurred were identified and compared, including single nucleotide polymorphisms (SNPs), insertions and deletions (InDels), and structural variations (SVs). The increase in the MIC of imipenem was proposed to be linked to mutations involved in polyamine biosynthesis, biofilm formation, OprD, and efflux pump functions. This study aims to clarify the underlying mechanism of imipenem resistance and provide alternative strategies for reducing resistance in P. aeruginosa. KEY POINTS: • Strains with different imipenem MIC were obtained via laboratory selection evolution. • Whole genomes of two strains with different MIC of imipenem were sequenced. • Underlying mechanism of imipenem resistance was clarified via comparative genomics.

Inhaled dry powder alginate oligosaccharide in cystic fibrosis: a randomised, double-blind, placebo-controlled, crossover phase 2b study

Background

OligoG is a low molecular-weight alginate oligosaccharide that improves the viscoelastic properties of cystic fibrosis (CF) mucus and disrupts biofilms, thereby potentiating the activity of antimicrobial agents. The efficacy of inhaled OligoG was evaluated in adult patients with CF.

Methods

A randomised, double-blind, placebo-controlled multicentre crossover study was used to demonstrate safety and efficacy of inhaled dry powder OligoG. Subjects were randomly allocated to receive OligoG 1050 mg per day (10 capsules three times daily) or matching placebo for 28 days, with 28-day washout periods following each treatment period. The primary end-point was absolute change in percentage predicted forced expiratory volume in 1 s (FEV₁) at the end of 28-day treatment. The intention-to-treat (ITT) population (n=65) was defined as randomised to treatment with at least one administration of study medication and post-dosing evaluation.

Results

In this study, 90 adult subjects were screened and 65 were randomised. Statistically significant improvement in FEV₁ was not observed in the ITT population. Adverse events included nasopharyngitis, cough and pulmonary exacerbation. The number and proportions of patients with adverse events and serious adverse events were similar between OligoG and placebo group.

Conclusions

Inhalation of OligoG-dry powder over 28 days was safe in adult CF subjects. Statistically significant improvement of FEV₁ was not reached. The planned analyses did not indicate a significant treatment benefit with OligoG compared to placebo. Post hoc exploratory analyses showed subgroup results that indicate that further studies of OligoG in this patient population are justified.

Inhalation of OligoG-DPI over 28 days was shown to be safe in adult CF subjects. Statistically significant improvement of FEV₁ was not reached. Post hoc subgroup analyses support mechanism of action for OligoG and warrant further prospective studies.https://bit.ly/2PHq6Z0

Microbiota from alginate oligosaccharide-dosed mice successfully mitigated small intestinal mucositis

BACKGROUND

The increasing incidence of cancer and intestinal mucositis induced by chemotherapeutics are causing worldwide concern. Many approaches such as fecal microbiota transplantation (FMT) have been used to minimize mucositis. However, it is still unknown whether FMT from a donor with beneficial gut microbiota results in more effective intestinal function in the recipient. Recently, we found that alginate oligosaccharides (AOS) benefit murine gut microbiota through increasing "beneficial" microbes to rescue busulfan induced mucositis.

RESULTS

In the current investigation, FMT from AOS-dosed mice improved small intestine function over FMT from control mice through the recovery of gene expression and an increase in the levels of cell junction proteins. FMT from AOS-dosed mice showed superior benefits over FMT from control mice on recipient gut microbiotas through an increase in "beneficial" microbes such as Leuconostocaceae and recovery in blood metabolome. Furthermore, the correlation of gut microbiota and blood metabolites suggested that the "beneficial" microbe Lactobacillales helped with the recovery of blood metabolites, while the "harmful" microbe Mycoplasmatales did not.

CONCLUSION

The data confirm our hypothesis that FMT from a donor with superior microbes leads to a more profound recovery of small intestinal function. We propose that gut microbiota from naturally produced AOS-treated donor may be used to prevent small intestinal mucositis induced by chemotherapeutics or other factors in recipients. Video Abstract.

Anti-Pathogenic Functions of Non-Digestible Oligosaccharides In Vitro

Non-digestible oligosaccharides (NDOs), complex carbohydrates that resist hydrolysis by salivary and intestinal digestive enzymes, fulfill a diversity of important biological roles. A lot of NDOs are known for their prebiotic properties by stimulating beneficial bacteria in the intestinal microbiota. Human milk oligosaccharides (HMOs) represent the first prebiotics that humans encounter in life. Inspired by these HMO structures, chemically-produced NDO structures (e.g., galacto-oligosaccharides and chito-oligosaccharides) have been recognized as valuable food additives and exert promising health effects. Besides their apparent ability to stimulate beneficial microbial species, oligosaccharides have shown to be important inhibitors of the development of pathogenic infections. Depending on the type and structural characteristics, oligosaccharides can exert a number of anti-pathogenic effects. The most described effect is their ability to act as a decoy receptor, thereby inhibiting adhesion of pathogens. Other ways of pathogenic inhibition, such as interference with pathogenic cell membrane and biofilm integrity and DNA transcription, are less investigated, but could be equally impactful. In this review, a comprehensive overview of In vitro anti-pathogenic properties of different NDOs and associated pathways are discussed. A framework is created categorizing all anti-pathogenic effects and providing insight into structural necessities for an oligosaccharide to exert one of these effects.

Multitarget Approaches against Multiresistant Superbugs

Despite efforts to develop new antibiotics, antibacterial resistance still develops too fast for drug discovery to keep pace. Often, resistance against a new drug develops even before it reaches the market. This continued resistance crisis has demonstrated that resistance to antibiotics with single protein targets develops too rapidly to be sustainable. Most successful long-established antibiotics target more than one molecule or possess targets, which are encoded by multiple genes. This realization has motivated a change in antibiotic development toward drug candidates with multiple targets. Some mechanisms of action presuppose multiple targets or at least multiple effects, such as targeting the cytoplasmic membrane or the carrier molecule bactoprenol phosphate and are therefore particularly promising. Moreover, combination therapy approaches are being developed to break antibiotic resistance or to sensitize bacteria to antibiotic action. In this Review, we provide an overview of antibacterial multitarget approaches and the mechanisms behind them.

Biochemical characterization and degradation pattern analysis of a novel PL-6 alginate lyase from Streptomyces coelicolor A3(2)

Alginate is the main component of brown algae which contributes to a huge biomass. The alginate oligosaccharides (AOs) have been widely used in food, cosmetic and pharmaceutical industries due to their various physiological activities. In this study, we expressed and characterized a novel PL-6 alginate lyase, named OUC-ScCD6. The results indicated that OUC-ScCD6 showed highest activity at 50 °C and pH 9.0. OUC-ScCD6 prefers to degrade poly M blocks and could digest poly G blocks as well. Endolytic action mode towards polysaccharides contributes to the creation of AOs with the degrees of polymerization 2-6. Degradation towards saturated oligosaccharides showed that saturated trisaccharides (M3 and G3) were minimum identifiable substrates. Furthermore, OUC-ScCD6 shows an even-numbered glycosidic bonds preference from non-reducing end which provided clearer insights into the substrate recognition and action mode of PL-6 family alginate lyases.

Alginate oligosaccharides improve germ cell development and testicular microenvironment to rescue busulfan disrupted spermatogenesis

Rationale: Busulfan is currently an indispensable anti-cancer drug, particularly for children, but the side effects on male reproduction are so serious that critical drug management is needed to minimize any negative impact. Meanwhile, alginate oligosaccharides (AOS) are natural products with many consequent advantages, that have attracted a great deal of pharmaceutical attention. In the current investigation, we performed single-cell RNA sequencing on murine testes treated with busulfan and/or AOS to define the mitigating effects of AOS on spermatogenesis at the single cell level.

Methods: Testicular cells (in vivo) were examined by single cell RNA sequencing analysis, histopathological analysis, immunofluorescence staining, and Western blotting. Testes samples (ex vivo) underwent RNA sequencing analysis. Blood and testicular metabolomes were determined by liquid chromatography-mass spectrometry (LC/MS).

Results: We found that AOS increased murine sperm concentration and motility, and rescued busulfan disrupted spermatogenesis through improving (i) the proportion of germ cells, (ii) gene expression important for spermatogenesis, and (iii) transcriptional factors in vivo. Furthermore, AOS promoted the ex vivo expression of genes important for spermatogenesis. Finally, our results showed that AOS improved blood and testis metabolomes as well as the gut microbiota to support the recovery of spermatogenesis.

Conclusions: AOS could be used to improve fertility in patients undergoing chemotherapy and to combat other factors that induce infertility in humans.

Single-cell RNA sequencing analysis reveals alginate oligosaccharides preventing chemotherapy-induced mucositis

Worldwide the incidence of cancer has been continuing increasing. Mucositis of the gastrointestinal tract is a common side effect in patients under chemotherapy. Anticancer drug busulfan, used for treating chronic myeloid leukemia especially in pediatric patients, causes mucositis of the gastrointestinal tract. Alginate oligosaccharides (AOS) are natural products with attractive pharmaceutical potentials. We aimed to investigate, at the single-cell level, AOS preventing small intestine mucositis induced by busulfan. We found that busulfan disturbed the endoplasmic reticulum and mitochondria of cells in the small intestine, damaged cell membranes especially cell junctions, and disrupted microvilli; all of which were rescued by AOS. Single-cell RNA sequencing analysis and functional enrichment analysis showed that AOS could recover small intestinal function. Deep analysis found that AOS improved the expression of transcriptional factors which explained AOS regulating gene expression to improve small intestine function. Further investigation in IPEC-J2 cells found that AOS acts its function through mannose receptor signaling pathway. Moreover, the improved blood metabolome confirmed small intestinal function was recovered by AOS. As a natural product with many advantages, AOS could be developed to assist in the recovery of intestinal functions in patients undergoing anticancer chemotherapy or other treatments.

Alginate Oligosaccharides Affect Mechanical Properties and Antifungal Activity of Alginate Buccal Films with Posaconazole

Sodium alginate and its oligosaccharides through potential antifungal properties might improve the activity of antifungal drugs enhancing their efficacy and potentially reducing the frequency of application. Mucoadhesive buccal films are oral dosage forms designed for maintaining both local or systemic drug effects and seem to be a very promising alternative to conventional oral formulations. Hence, in this study, mucoadhesive buccal films based on the alginate and its oligosaccharide oligomer composed predominantly of mannuronic acid for the administration of posaconazole-antifungal drug from the azole group were developed. As the polymer gelation method, a relatively new freeze-thaw technique was chosen. All prepared formulations were examined for pharmaceutical tests, swelling, mechanical, and mucoadhesive properties. In addition, the influence of sodium alginate (ALG) and alginate oligosaccharides (OLG) on POS antifungal activity on Candida species was performed. It was observed that film formulation containing 1% ALG and 1% OLG (F2) was characterized by optimal mucoadhesive and swelling properties and prolonged drug release up to 5 h. Additionally, it was shown that OLG affected the growth reduction of all tested Candida spp. The obtained data has opened the way for future research for developing OLG-based dosage forms, which might increase the activity of antifungal drugs.

Cellulose Nanofibril Formulations Incorporating a Low-Molecular-Weight Alginate Oligosaccharide Modify Bacterial Biofilm Development

Cellulose nanofibrils (CNFs) from wood pulp are a renewable material possessing advantages for biomedical applications because of their customizable porosity, mechanical strength, translucency, and environmental biodegradability. Here, we investigated the growth of multispecies wound biofilms on CNF formulated as aerogels and films incorporating the low-molecular-weight alginate oligosaccharide OligoG CF-5/20 to evaluate their structural and antimicrobial properties. Overnight microbial cultures were adjusted to 2.8 × 10⁹ colony-forming units (cfu) mL^-1 in Mueller Hinton broth and growth rates of Pseudomonas aeruginosa PAO1 and Staphylococcus aureus 1061A monitored for 24 h in CNF dispersions sterilized by γ-irradiation. Two CNF formulations were prepared (20 g m^-2) with CNF as air-dried films or freeze-dried aerogels, with or without incorporation of an antimicrobial alginate oligosaccharide (OligoG CF-5/20) as a surface coating or bionanocomposite, respectively. The materials were structurally characterized by scanning electron microscopy (SEM) and laser profilometry (LP). The antimicrobial properties of the formulations were assessed using single- and mixed-species biofilms grown on the materials and analyzed using LIVE/DEAD staining with confocal laser scanning microscopy (CLSM) and COMSTAT software. OligoG-CNF suspensions significantly decreased the growth of both bacterial strains at OligoG concentrations >2.58% (P < 0.05). SEM showed that aerogel-OligoG bionanocomposite formulations had a more open three-dimensional structure, whereas LP showed that film formulations coated with OligoG were significantly smoother than untreated films or films incorporating PEG400 as a plasticizer (P < 0.05). CLSM of biofilms grown on films incorporating OligoG demonstrated altered biofilm architecture, with reduced biomass and decreased cell viability. The OligoG-CNF formulations as aerogels or films both inhibited pyocyanin production (P < 0.05). These novel CNF formulations or bionanocomposites were able to modify bacterial growth, biofilm development, and virulence factor production in vitro. These data support the potential of OligoG and CNF bionanocomposites for use in biomedical applications where prevention of infection or biofilm growth is required.