Academic journal article Journal of Sustainable Development

Biocompatible Hydrogel from a Green Tide-Forming Chiorophyta

Academic journal article Journal of Sustainable Development

Biocompatible Hydrogel from a Green Tide-Forming Chiorophyta

Article excerpt

Abstract

The green-tide chlorophyta Ulva contains the functional acidic polysaccharide ulvan in its cell wall. Here, we focused on the development of a novel soft material that can be used as a biocompatible ion exchanger. Combining chitosan and ulvan solutions was found to yield a hydrogel with various functions. This ulvan-chitosan polyion complex gel was more stable than an alginic acid-chitosan gel under both acidic and basic conditions. However, an ulvan-chitosan gel-coated vessel showed only a mild effect of preventing blood clotting, whereas a heparin-chitosan gel-coated vessel prolonged clotting time. In terms of the ion-exchange behavior, the ratio of the CuSO^sub 4^-concentration in a CuSO^sub 4^ solution treated with the gel to that in a solution without the gel showed that increasing the initial CuSO^sub 4^ concentration increased CuSO^sub 4^ adsorption in the gel. These studies show that this novel hydrogel can be used as an ion exchanger as well as in other applications.

Keywords: Soft material, Ulvan, Chitosan, Polyion complex, Green-tide chlorophyta, Ion exchange

1. Introduction

A study on the economics of ecosystems and biodiversity has revealed the importance of biodiversity for economics (Bishop et al., 2010). Wise use of biodiversity is important for sustainable development because ecosystem services are provided by biodiversity. Scientific approaches to sustainable development have been reported in various fields such as nature conservation (Alvarez, 2010), chemical technologies for recycling plastics (Chen, 2006), materials science (Wu et al., 2009), and education for the wise use of biodiversity (Kanno et al., 2011). At the 10th conference of the parties of the convention on biological diversity (CBD-COP10) held in Nagoya, Japan, delegates from more than 100 countries agreed on the new strategic plan of the Convention on Biological Diversity (CBD), namely, the 'The Aichi Biodiversity Targets' (Strategic Plan for 2020 and the Aichi Targets, 2010). The Strategic Plan is comprised of a shared vision, a mission, strategic goals, and 20 ambitious yet achievable targets. A study on the utilization of species that are both problematic and a resource is one of the possible ways to achieve strategic goal B of the Aichi Targets-to reduce the direct pressures on biodiversity and promote sustainable use.

For species that are both problematic (e.g., invasive) and a resource, various means have been employed to increase their utility and thereby, in some cases, to reduce their environmental impact. New Zealand used the hair of the invasive possum by mixing it with lamb's wool and angora to produce wool. Another example is that of the crab. Although not an invasive alien species, a vast amount of crab shell waste is released by the aquatic food industry, creating an environmental problem. Chitin is a polysaccharide found in crab shells, shellfish, insects, and some fungi. A number of investigations on chitin and chitosan revealed that they possessed biological activities such as anti-bacterial effects. This research added value to crab shell waste to produce novel valuable materials.

Green algae blooms, which are often referred to as "green tides" occur throughout the world. Local self-governing bodies and NGOs (non-governmental organizations) engage in removing the algal mats from mudflat because they devastate the scenery and emit a foul odor. In Fukuoka, Japan, green tides and algal mats are removed by special ships, heavy machinery, and volunteer workers (Figure 1). Algal mats are incinerated or buried in landfills in Hakata bay. The Wajiro tideland is important because it is where the black-faced spoonbill (Platalea minor), an endangered species that numbers less than 1,000 worldwide, passes the winter. Although the seaweed Ulva is a natural resource, it is also an environmental challenge because it causes algal blooms. Pollution and nutrient loading (e.g., of nitrogen and phosphorous) can result in an increase in seaweed growth and a resultant lack of oxygen because of rotting seaweed on the mudflats, and many animals living in the mud under the rotting Ulva suffocate (Donna et al. …

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