Metal Removal by Seaweed Biomass

Environmental metal pollution is a serious public problem, and it has become an issue leading to research in the effluent remediation area. Techniques involving biosorption processes have been found to be promising due to the low cost of nonliving biomaterials, which have the potential to adsorb metal ions from wastewaters. One of the most promising types of biomasses to be used as biosorbents is the seaweed biomass, particularly from brown algae. The biosorption capability of the seaweed biomass relies on their cell wall chemical composition, mainly composed of alginates and fucoidans, molecules with a high presence of functional groups that interact with metal ions. This book chapter focuses on the use of seaweed biomass for metal biosorption and the chemical basis underlying the process. The current state of the commercial status of biosorption technology based on seaweed biomass is presented. Examples of complementary uses of the algae biomass other than industrial wastewater cleaning processes are presented, and the potential reuse of the biomass after the biosorption focused on biofuel production is discussed

Materials of marine origin: a review on polymers and ceramics of biomedical interest

Marine organisms are constituted by materials with a vast range of properties and characteristics that may justify their potential application within the biomedical field. Moreover, assuring the sustainable exploitation of natural marine resources, the valorisation of residues from marine origin, like those obtained from food processing, constitutes a highly interesting platform for development of novel biomaterials, with both economic and environmental benefits. In this perspective, an increasing number of different types of compounds are being isolated from aquatic organisms and transformed into profitable products for health applications, including controlled drug delivery and tissue engineering devices. This report reviews the work that is being developed on the isolation and characterisation of some polysaccharides, proteins, glycosaminoglycans and ceramics from marine raw materials. Emphasis is given to agar, alginates, carrageenans, chitin and chitosan, among other polysaccharides, collagen, glycosaminoglycans such as chondroitin sulphate, heparin and hyaluronic acid, calcium phosphorous compounds and biosilica. Finally, this report ends by reviewing the application of the previously mentioned materials on specific biomedical applications, in particular their participation on the development of controlled drug delivery systems and tissue engineering scaffolds.European Fund for Regional Development (EFRD)Fundação para a Ciência e a Tecnologia (FCT

Studies of nanoparticles-bacteria interactions to develop potential bio-based reagents for separation of fine mineral particles.

The increasing demand for minerals worldwide and the depletion of high-grade ores necessitate the extraction of minerals from low-grade ores. This requires processing the low-grade ores to fine and ultra-fine particles to liberate the minerals. But separating fine mineral particles via flotation is challenging and the process requires reagents with a large environmental imprint. Therefore, as an effective and eco-friendly alternative, the work in the present doctoral thesis explores the use of microbes and microbe-derived metabolites as potential reagents (biocollectors/bioflocculants) for the separation of ultrafine mineral particles. The main work has been done on an actinomycetes bacterium Rhodococcus opacus. It has a unique cell wall structure, marked by the presence of mycolic acids (2-alkyl, 3-hydroxy fatty acids). Mycolic acids impart hydrophobicity to the cell envelope of R. opacus. Hence, the cells have been explored for separating various minerals in previous studies. But most of these studies were on micro-range minerals, but here we explored its use for the separation of minerals that are in the nano-range. In this work, the cells were genetically modified and also naturally through adaptation to the inhibitory substances to use them for mineral separation. The cells were adapted to the metal oxide nanoparticles (used as model systems for the nano-range minerals). Adapted cells showed changed surface properties, and they could be used as excellent bioflocculants for the separation of ultra-fine mineral particles. Polysaccharides are also reported to work as good flocculating agents therefore, further, we explored the flocculating potential of the fully characterized alginates from Pseudomonas fluorescens and Laminaria hyperborea, for metal oxide nanoparticles. It was found that the alginates' flocculating property depends on their composition and the cations used to form the gel

Acetylation of Seaweed Alginate by Pseudomonas Syringae.

Acetylation of bacterial alginate by Pseudomonas syringae subsp. phaseolicola ATCC 19304 was independent of alginate biosynthesis. This allowed the development of a process for acetylating seaweed alginate using immobilized P. syringae ATCC 19304 cells. About 50% of the mannuronic acid residues of seaweed alginate were acetylated by carbon immobilized P. syringae cells in a fluidized bed, up-flow reactor system fed continuously with seaweed alginate and gluconic acid. O-Acetylation by this process was found to be specific for the C-2 and/or C-3 position(s) of mannuronate residues. Acetylated seaweed alginate showed altered properties including increased viscosity and changed affinities for some cations

Inter-Grade and Inter-Batch Variability of Pharmaceutical-Grade Sodium Alginate

Polymeric excipients are generally the least well-characterized components of pharmaceutical formulations. The aim of this dissertation work is to facilitate the quality-by-design (QbD) approach to pharmaceutical formulation and manufacturing by evaluating the inter-grade and inter-batch variability of pharmaceutical-grade polymeric excipients. Sodium alginate, a widely used polymeric excipient, was selected for evaluation using appropriate analytical methods and test conditions, especially rheological methods. The materials used were six different grades of sodium alginate and an additional ten batches of one of the grades. To compare the six grades, steady shear measurements were conducted on solutions at 1, 2, and 3% w/w, consistent with their use as thickening or binding agents. Small amplitude oscillation (SAO) measurements were conducted on sodium alginate solutions at higher concentrations (4-13% w/w) corresponding to their use in controlled release matrices. In order to compare the ten batches of one grade, steady shear and SAO measurements were performed on their solutions at 2% w/w and 8% w/w, respectively. Results show that rheological properties of sodium alginate solutions are influenced by both molecular weight and chemical composition of sodium alginate. ¡§One-point¡¨ apparent viscosity data obtained at one low concentration and one shear rate is not representative of the complex rheological behavior of various grades of sodium alginate solutions at higher concentrations or other shear rates. The potential interchangeability of these different grades used as thickening or binding agents could be established by comparing the apparent viscosities of their solutions as a function of both alginate concentration and shear conditions. For sodium alginate used in controlled release formulations, both steady shear (at one low concentration, e.g., 2% w/w) and SAO measurements (at one high concentration indicative of polymer gel state, e.g., 8% w/w) are recommended to be performed on sodium alginate solutions to ensure interchangeability. Furthermore, among batches of the same grade, significant differences in rheological properties were observed, especially at the high solution concentration (i.e., 8% w/w). In summary, inter-grade and inter-batch variability of sodium alginate can be determined using steady shear and SAO methods. The influence of inter-grade and inter-batch variability of sodium alginate on the functionality of sodium alginate used in matrix tablets was investigated with a focus on compression properties, swelling, erosion behavior of alginate matrix tablets, and drug release from matrix tablets. The compression behavior of four grades and three batches of sodium alginate were studied by compaction energetics, out-of-die Gurnham, and out-of-die Heckel analysis. It was found that sodium alginates deform less plastically than microcrystalline cellulose (MCC PH102) but similar to lactose anhydrous. Sodium alginates also demonstrate more elastic deformations during compression than both MCC PH102 and lactose anhydrous. Compacts prepared from multiple batches of the same grade varied in porosity. The same tensile strength of compacts can be achieved by compressing the multiple batches to the same porosity. Sodium alginate tablets undergo both swelling and erosion in water. Grades with substantially higher apparent viscosities at low solution concentration exhibit a higher percentage of water uptake and a low percentage of erosion. Those batches not significantly different in their apparent viscosities at low solution concentration but significantly different in viscoelasticity at high solution concentrations do demonstrate significant differences in their swelling and erosion behavior. Acetaminophen release from sodium alginate matrix tablets prepared from the four grades and three batches can be well described by a zero-order equation. Significant differences in release profile were observed among various grades and batches. In conclusion, the inter-grade and inter-batch variability of sodium alginate has a significant influence on the swelling, erosion, and drug release behavior of sodium alginate matrix tablets. Apparent viscosities of sodium alginate solution at low concentration alone are not sufficient to predict the functionality of sodium alginate used in matrix tablets. Viscoelastic properties of sodium alginate solutions at high concentrations indicative of polymer gel state are appropriate to be characterized. Further study was conducted to determine whether sodium alginate solutions\u27 rheological parameters are relevant to sodium alginate\u27s use in the formulation of calcium alginate gels. Among the grades with similar guluronic acid percentage (%G), there is a significant correlation between gel fracture force and apparent viscosity. However, the results for the partial correlation analysis for all six grades of sodium alginate show that gel fracture force is significantly correlated with %G, but not with the rheological properties of the sodium alginate solutions. Studies of the ten batches of one grade of sodium alginate show that apparent viscosities of their solutions do not correlate with gel fracture force while tan δ values are significantly, but minimally, correlated to gel fracture force. Inter-batch differences in the rheological behavior for one specific grade of sodium alginate are insufficient to predict the corresponding calcium alginate gel\u27s mechanical properties. In summary, rheological methods, including steady shear and small amplitude oscillation, are able to identify the inter-grade and inter-batch variability of sodium alginate. Inter-grade and inter-batch variability of sodium alginate could lead to substantial differences in the functionality of sodium alginate in matrix tablets and in calcium alginate gels. Rheological properties of sodium alginate in solution are suggestive of its functionality as thickeners, or as controlled release agent. However, rheological properties of sodium alginate in solution do not seem to be sufficient to predict the mechanical properties of the corresponding calcium alginate gels

Antimicrobial wafers as a novel technology for infection control in chronic wounds.

Bacterial contamination and persistent infection is a common cause of impaired wound healing. Generally, non-healing wounds display similar physiological features with regards to mixed bacterial flora, ischemia and production of exudate. The application of topical, broad spectrum antimicrobial compounds embedded in absorbent dressings has been shown to control bioburden and improve healing. Lyophilised, biopolymeric antimicrobial wafers can offer a contemporary, user-friendly, self-adhesive and effective approach for the management of suppuration and polybacterial contamination in a wide range of non-healing wounds. Cohesive, non-friable, porous, disc shape wafers were successfully produced with sodium alginate (SA) (18.17 plusminus 0.70 Pa.s), guar gum (GG) (82.21 plusminus 5.41 Pa.s; 95.87 plusminus 2.31 Pa), xanthan gum (XG) (2.86 plusminus 0.12 Pa.s; 23.61 plusminus 0.68 Pa), karaya gum (KAG) (12.89 plusminus 0.93 Pa.s) and an original gel consisting of a blend of a synergistic SA-KAG (7.75 plusminus 0.64 Pa.s; 86.34 plusminus 5.19 Pa) (1:1 ratio). Clinical concentrations of the broad spectrum, topical, antimicrobial compounds, neomycin sulphate (0.5 % w/v NS), chlorhexidine digluconate (0.5 % v/v CHD), povidone iodine (1.0 % v/v PVP-I) and silver sulfadiazine (1.0 % w/v SS) were mixed with compatible biopolymers and appeared to alter the rheological properties of the biopolymers. Rheological analysis of pre-lyophilised gels was undertaken to quantify the flow properties of the gels. The necessity of producing sterile wafers was investigated by exposing all biopolymer-antimicrobial combinations to 25 and 40 kGy of gamma irradiation. Gamma-rays caused total degradation of GG, KAG, SA and SA-KAG, while XG appeared to withstand irradiation. A novel free standing dissolution raft (FSDR) was designed and used to quantify the CHD released from both gels and wafers. CHD released from wafers ranged from 3.5 plusminus 0.01 to 17.4 plusminus 0.39 %. Gels and wafers released CHD in a sustained manner and the release profile of wafers was similar to the respective gels, with the exception of GG. Neither gels nor wafers released 100% of the incorporated antimicrobial indicating that drug-polymer interactions governed the general performance of antimicrobial wafers, in terms of adhesion, expansion ratio (ER), inhibition ratio (IR), water uptake capacity (WUC) and antimicrobial delivery. Molecular modelling studies undertaken for KAG-antimicrobial complexes demonstrated an unusual Z-shape geometry for cationic CHD. The charge and geometry of CHD was plausibly responsible for the antimicrobials entrapment within biopolymeric networks. The efficacy of antimicrobial wafers was demonstrated in vitro under simulated conditions of an exuding wound using modified disc diffusion and an original antimicrobial diffusion cell (ADC). All wafers were effective in vitro against common chronic wound pathogens of such as methicillin-resistant Staphylococcus aureus (MRSA), methicillin-sensitive Staphylococcus aureus (MSSA), E. coli and P. aeruginosa. Antimicrobial activity depended on the sensitivity of the microorganisms to a specific antimicrobial compound and the presence of organic material. Data obtained demonstrated that the presence of protein (BSA) in the pseudo-exudate inhibited the antimicrobial activity of CHD and PVP-I, while enhancing the antimicrobial activity of SS and NS against MRSA. The general findings summarised in this thesis conclude that factors such as protein content, electrolyte content and pH of exudate play a key role in the efficacy of self-adhesive, absorbent formulations intended for the topical delivery of antimicrobial compounds to non-healing, infected wounds. Drug-polymer interactions developed between biopolymers and incorporated antimicrobial compounds have a profound effect on the general performance of lyophilised antimicrobial wafers

Recent Developments of Carboxymethyl Cellulose.

Carboxymethyl cellulose (CMC) is one of the most promising cellulose derivatives. Due to its characteristic surface properties, mechanical strength, tunable hydrophilicity, viscous properties, availability and abundance of raw materials, low-cost synthesis process, and likewise many contrasting aspects, it is now widely used in various advanced application fields, for example, food, paper, textile, and pharmaceutical industries, biomedical engineering, wastewater treatment, energy production, and storage energy production, and storage and so on. Many research articles have been reported on CMC, depending on their sources and application fields. Thus, a comprehensive and well-organized review is in great demand that can provide an up-to-date and in-depth review on CMC. Herein, this review aims to provide compact information of the synthesis to the advanced applications of this material in various fields. Finally, this article covers the insights of future CMC research that could guide researchers working in this prominent field