A simple, high throughput method for the quantification of sodium alginates on oesophageal mucosa

All-Aqueous Freeform Fabrication of Perfusable Self-Standing Soft Compartments

Compartmentalized structures obtained in all-aqueous settings have shown promising properties as cell encapsulation devices, as well as reactors for trans-membrane chemical reactions. While most approaches focus on the preparation of spherical devices, advances on the production of complex architectures have been enabled by the interfacial stability conferred by emulsion systems, namely mild aqueous two-phase systems (ATPS), or non-equilibrated analogues. However, the application of non-spherical structures has mostly been reported while keeping the fabricated materials at a stable interface, limiting the free-standing character, mobility and transposition of the obtained structures to different setups. Here, the fabrication of self-standing, malleable and perfusable tubular systems through all-aqueous interfacial assembly is shown, culminating in the preparation of independent objects with stability and homogeneity after disruption of the polymer-based aqueous separating system. Those hollow structures can be fabricated with a variety of widths, and rapidly printed as long structures at flow rates of 15 mm s^-1 . The materials are used as compartments for cell culture, showcasing high cytocompatibility, and can be tailored to promote cell adhesion. Such structures may find application in fields that benefit from freeform tubular structures, including the biomedical field with, for example, cell encapsulation, and benchtop preparation of microfluidic devices.

Players over the Surface: Unraveling the Role of Exopolysaccharides in Zinc Biosorption by Fluorescent Pseudomonas Strain Psd

Fluorescent Pseudomonas strain Psd is a soil isolate, possessing multiple plant growth promoting (PGP) properties and biocontrol potential. In addition, the strain also possesses high Zn²⁺ biosorption capability. In this study, we have investigated the role exopolysaccharides (EPS) play in Zn²⁺ biosorption. We have identified that alginates are the prime components contributing to Zn²⁺ biosorption. Deletion of the alg8 gene, which codes for a sub-unit of alginate polymerase, led to a significant reduction in EPS production by the organism. We have also demonstrated that the increased alginate production in response to Zn²⁺ exposure leads to improved biofilm formation by the strain. In the alg8 deletion mutant, however, biofilm formation was severely compromised. Further, we have studied the functional implications of Zn²⁺ biosorption by Pseudomonas strain Psd by demonstrating the effect on the PGP and biocontrol potential of the strain.

Method for quantifying alginate and determining release from a food vehicle in gastrointestinal digesta

To assess the efficacy of alginate as a modifier of enzyme activity, a suitable method to quantify its release must be developed. This paper develops and assesses the ability of the Periodic Acid Schiffs (PAS) assay to quantify alginate, and its release from bread during digestion in a model gut. Control and alginate enriched (4% w/w wet dough) bread were used. A model gut replicating the mouth, stomach and small intestines was used. Standard curves were created for alginate in deionised H2O and model gut solutions using a modified PAS to remove interference. The PAS assay quantified alginate with excellent linearity (R(2)=0.99), and optical density range (0.02-0.5). There was a significant difference in alginate release at 180 min compared to 0 and 60 min. The data indicate the modified PAS assay is a simple method for quantifying alginate release and release rate from alginate enriched products.

Synchronized release of Doxil and Nutlin-3 by remote degradation of polysaccharide matrices and its possible use in the local treatment of colorectal cancer

A novel approach to the prevention of colorectal cancer (CRC) recurrence by the local, luminal application of the combined therapies: Nutlin-3 (NUT) and the liposomal preparation of doxorubicin, Doxil(*) (Doxil) is presented here. The two drug entities were loaded into calcium alginate beads, engineered to erode upon exposure to a de-crosslinking agent, to allow for the controlled, concomitant release of the two. The synchronized release-driven improved cytotoxicity of NUT and Doxil was tested in vitro in RKO (wild-type p53) and HT-29 (mutant p53) CRC cells, by measuring intracellular expression of p53, p21 and Mdm2, as well as monitoring cell proliferation and viable cell numbers. NUT treatment alone was identified to be cytotoxic exclusively towards RKO cells. However, coadministration of NUT enhanced Doxil's anti-proliferative effects and cell death induction in a synergistic manner in both cell types. It was also identified that combinatorial treatment in a wt p53 context affected the p53 pathway by elevating the expression of p53 and its target p21. The capability of the formulation to erode in the presence of a de-crosslinking agent was demonstrated in vivo in the cecum of the anesthetized rat using indomethacin as a poorly water-soluble PK probe.

Novel preparation techniques for alginate-poloxamer microparticles controlling protein release on mucosal surfaces

The objective of this study was to develop novel preparation techniques for protein-loaded, controlled release alginate-poloxamer microparticles with a size range suitable for pulmonary administration. Bovine serum albumin (BSA)-loaded microparticles were prepared by spray-drying aqueous polymer-drug solutions, followed by cross-linking the particles in aqueous or ethanolic CaCl(2) or aqueous ZnSO(4) solutions. The microparticles were characterized with respect to their morphology (optical and scanning electron microscopy), particle size (laser light diffraction), calcium content (atom absorption spectroscopy), alginate content (complexation with 1,9-dimethyl methylene blue) and in vitro drug release (modified Franz diffusion cell). The spray-dried microparticles were spherical in shape with a size range of 4-6μm. Aqueous cross-linking led to a significant size increase (10-15μm), whereas ethanolic cross-linking did not. The substantial drug loss (∼50%) during aqueous CaCl(2) cross-linking could be avoided by using aqueous ZnSO(4) or ethanolic CaCl(2) solutions. Protein release from microparticles cross-linked with ethanolic CaCl(2) solutions was much faster than in the case of aqueous CaCl(2) solutions, probably due to the lower calcium content. The salt concentration and temperature of the cross-linking solutions also affected the composition of and drug release from the microparticles. Cross-linked alginate-poloxamer microparticles can be produced in a size range appropriate for deep lung delivery and with controlled protein release kinetics (time frame: hours to days) with these novel preparation techniques. The systems offer an interesting potential for the controlled mucosal delivery of protein drugs.

Oesophageal bioadhesion of sodium alginate suspensions

Sodium alginate suspensions in a range of water miscible vehicles were investigated as novel bioadhesive liquids for targeting the oesophageal mucosa. Such a dosage form might be utilised to coat the oesophageal surface and provide a protective barrier against gastric reflux, or to deliver therapeutic agents site-specifically. Alginate suspensions swelled and formed an adherent viscous layer on contact with the mucosa. The swelling kinetics of alginate particles on the oesophageal surface was examined with respect to vehicle composition and related to the extent, duration and location of bioadhesion within the oesophagus. Mucosal retention was evaluated in two in vitro models utilising tissue immersion and a peristaltic tube. By varying the vehicle composition it was possible to modulate the rate of swelling of alginate particles on the mucosa and the mucosal retention of suspensions. Suspensions containing predominantly glycerol exhibited superior retention and were preferentially retained within the lower oesophagus. The propensity of these suspensions to rapidly swell on the mucosa and establish adhesive/cohesive bonds may explain their enhanced retention. The potential to control, through vehicle composition, the extent, duration and location of oesophageal retention could provide a useful tool for site targeting of viscous polymers to the oesophagus.

Oesophageal bioadhesion of sodium alginate suspensions: particle swelling and mucosal retention

This paper describes a prospective bioadhesive liquid dosage form designed to specifically adhere to the oesophageal mucosa. It contains a swelling polymer, sodium alginate, suspended in a water-miscible vehicle and is activated by dilution with saliva to form an adherent layer of polymer on the mucosal surface. The swelling of alginate particles and the bioadhesion of 40% (w/w) sodium alginate suspensions were investigated in a range of vehicles: glycerol, propylene glycol, PEG 200 and PEG 400. Swelling of particles as a function of vehicle dilution with artificial saliva was quantified microscopically using 1,9-dimethyl methylene blue (DMMB) as a visualising agent. The minimum vehicle dilution to initiate swelling varied between vehicles: glycerol required 30% (w/w) dilution whereas PEG 400 required nearly 60% (w/w). Swelling commenced when the Hildebrand solubility parameter of the diluted vehicle was raised to 37 MPa(1/2). The bioadhesive properties of suspensions were examined by quantifying the amount of sodium alginate retained on oesophageal mucosa after washing in artificial saliva. Suspensions exhibited considerable mucoretention and strong correlations were obtained between mucosal retention, the minimum dilution to initiate swelling, and the vehicle Hildebrand solubility parameter. These relationships may allow predictive design of suspensions with specific mucoretentive properties, through judicious choice of vehicle characteristics.