Turbinaria Ornata Descriptive Essay

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Description: Plants erect and stiff, 2-20(-30) cm long when reproductive. Plants isolated or in small groups, but occasionally forming low mats, especially in rocky intertidal habitats. Mostly light yellowish brown to dark brown in color when living, but occasionally light grayish or even yellowish white. Holdfast conical or irregular, usually with several unbranched or dichotomously branched stolons growing from basal area of the erect axes. Small juvenile plants with flattened leaves. These leaves and the stolons of larger plants can attach to the substratum and initiate new plants. One cylindrical main axis growing from the holdfast. Larger plants often with secondary branching; rarely with higher orders of branching. Leaves with a petiole and a double row of stiff spines around the margin of the leaves in apical view. Petiole cylindrical near base, becoming triangularly compressed in distal portions. Many buy not all plants have some leaves with hollow centers functioning as floats. Receptacles in tight branched clusters, mostly cylindrical, to 1.5 cm long, with rounded blunt apecies; developing in the leaf petiole near the base.

Introduction and Origin: Native to Hawaii.

Hawaiian Distribution: Molokai, Hawaii, Lanai, Maui, Laysan, Nihoa, Oahu, Kure, Necker, Lisianski, French Frigate Schoals, Pearl and Hermes Reef, Kauai.

Habitat: Very common, found in a wide variety of habitats including exposed rocky intertidal areas, tide pools, intertidal benches, reef flats and in deeper water. Mid intertidal to at least 30 m. Sometimes the most abundant large alga on reef flats in waters from

Environmental Effects: Not studied. May affect recruitment of other species by successfully competing for substrate.

World Distribution: Widely distributed in tropical and subtropical areas of the central and western Pacific and Indian Oceans.

Commercial Interests: None.

Rate of Spread / Method: Growth rate unknown. In a Tahitian coral reef, settlement patterns of germlings observed in situ was limited to within 90 cm of the parental thalli, and the greatest number of settled germlings was observed during the cold season. Dispersal of germlings appears to be influenced by the dominant current during their release. This short-distance dispersal allows rapid establishment and maintenance of local populations. Not all oogonia present were released. The number of oogonia produced varied seasonally, being lower during the hot season (Stiger & Payri, 1999).

Factors likely to influence Spread and Distribution: Temperature, nutrients availability.

Reasons for Success: The particular morphology of the thallus withstands exposure and high wave action. The tendency for fertile thalli to float over long distances, combined with the keeping of part of their oogonia, and high settlement efficiencies, could account for its capacity to colonize new areas (Stiger & Payri, 1999).

Control Methods: None used.

References: Stiger, V. and Payri, C. E. (1999) Spatial and temporal patterns of settlement of the brown macroalgae Turbinaria ornata and Sargassum mangarevense in a coral reef on Tahiti. Marine Ecol. Progress Series 191:91-100

1. Introduction

Nanoparticles have attracted significant attention due to their various applications in the fields of biotechnology and biomedical sciences. The term nanogel is frequently used to define aqueous dispersions of hydrogel particles composed of nanoscale-sized physically or chemically cross-linked polymer networks [1]. Their application in medicine is very promising since they exhibit high stability and loading capacity, as well as responsiveness to environmental factors such as pH, ionic strength and temperature, making them viable candidates for transport and drug release. However, when nanoparticles enter the bloodstream they are often opsonized by plasma proteins and/or rapidly removed from the blood by the mononuclear phagocytic system [2]. Hydrophobic particles are typically opsonized much faster than their hydrophilic counterparts [3]. Several researchers have focused on the camouflaging or masking of nanoparticle surfaces to avoid these events. As a result, some polymers have been evaluated as protecting groups, including polyacrylamides, polyvinyl alcohol (PVA), poly(ethylene glycol) (PEG) and polysaccharides [4].

Recently, self-assembled nanoparticles based on natural polysaccharides have been of particular interest in light of their good biocompatibility, biodegradability, reduced toxic side effects and improved therapeutic effects [5]. Another advantage of using polysaccharides is that these molecules contain reactive groups which can be used to introduce different chemical ligands [6]. For example, polysaccharides can be used to synthesize water-soluble polymers with grafted hydrophobic molecules, that is, amphiphile polymers [7]. Through self-assembly, hydrophobic regions are directed from outside the molecule to form an inner core surrounded by hydrophilic chains. This type of structure is suitable for trapping hydrophobic substances such as hydrophobic drugs [8].

Recently, Bae and colleagues [9] reported that heparin nanogels were able to induce apoptosis in tumor cells. The authors attributed antitumor activity to heparin, a sulfated polysaccharide exhibiting several biological activities. Of these, the most noteworthy and widely studied is anticoagulant activity [10]. Pharmaceutical-grade heparin is derived from porcine intestinal mucosa through several steps of purification. However, the amount of heparin obtained from each animal is small and may be accompanied by impurities, including other sulfated polysaccharides and proteins [11]. Sulfated polysaccharides from seaweed, such as sulfated fucans, are an alternative to heparin.

Synthesis of nanoparticles from fucans is still new and to the best of our knowledge only one article exists describing this process [12]. Sulfated fucans comprise families of polydisperse polysaccharides based on sulfated L-fucose. Heterofucans are also known as fucoidans and are not widespread in nature, occurring only in brown seaweed and tunicates [13,14], with seaweeds being the most important source of fucans. Seaweed synthesizes fucan and displays unique structural characteristics reflected in the biological, pharmacological and biotechnological properties of the polysaccharide. Furthermore, these structural characteristics can be modified by biotic and abiotic factors that seaweed is exposed to, as well as extraction and purification methods used to obtain sulfated polysaccharides. Recent reviews regarding seaweed fucans have been restricted to their structural characteristics and primary biological/pharmacological activities [15].

The brown seaweed Spatoglossum schröederi synthesizes three heterofucans, namely fucan A, fucan B and fucan C. Our group proposes 21 kDa fucan A structure as consisting of a core of β(1–3) glucuronic acid-containing 4.5 kDa oligosaccharide, with branches at C-4 of α(1–3)-linked fucose chains. Fucose is substituted at C-4 and C-2 (minor) with sulfate groups. In addition, some fucose residues are substituted at C-2 with chains of β(1–4) xylose, which, in turn, is also partially sulfated (Figure 1) [16]. This fucan displayed no mutagenicity or genotoxicity [17]. In addition, fucan A shows no toxicity in vivo [18]. Thus, in the present study we synthesized and characterized hydrophobically modified fucan A nanogel (SNFuc), assessing their effect on several tumor and normal cell lines.

Figure 1. Structure of fucan A from Spatoglossum schroederi proposed by Leite and colleagues [16].

Figure 1. Structure of fucan A from Spatoglossum schroederi proposed by Leite and colleagues [16].

2. Results and Discussion

2.1. FT-IR Analysis

The FI-IR analysis of native fucan and SNFuc is showed in Figure 2. Characteristic sulfate absorptions were identified in the FT-IR spectra of compounds: bands around 1274 cm−1 for asymmetric S=O stretching vibration and bands around 1045 cm−1 for symmetric C–O vibration associated with a C–O–SO3 group. The peaks at 810–850 were caused by the bending vibration of C–O–S [19]. At 3000–3400 cm−1 Fuc A and SNFuc showed bands from the stretching vibration of O–H and C–H, respectively [20]. However, the SNFuc FI-IR spectrum showed the intensity of these bands increased due the presence of N–H (3000–3400 cm−1) and stretching vibrations of CH2 in hexadecyl residues (2921 and around 2850 cm−1) [21]. The peak of the C–H symmetric deformation vibration was at 1427 cm−1 [22]. The intensities of this absorption band increased with chain length of the CH2 groups in SNFuc. A band at 1616 cm−1 was identified only in fucan A spectrum and was assigned to antisymmetric stretching vibration of COO of glucuronic acid [23]. The presence glucuronic acid was also confirmed with a symmetric vibration peak around 1410 cm−1. On the other hand, SNFuc spectrum showed a band at 1740 cm−1 caused by C=O stretch vibrations in COOH and esters [24]. The band at1643 cm−1 was due the amine I vibration which is overlapped with the vibration of water. Less intense peak around1550 cm−1 arose from amide II vibration in alkylamides and thus confirmed amidation. Additionally, band at 620 cm−1 was assigned to N–C=O bending vibration [24].

Figure 2. FTIR spectra of native fucan and SNFuc.

Figure 2. FTIR spectra of native fucan and SNFuc.

2.2. 1H NMR and Elemental Analysis

The native fucan A 1H NMR spectrum is shown in Figure 3A. The two main α-anomeric protons, which correspond to α-L-fucose units, were observed at 5.18 and 5.08 ppm. In contrast with the simplicity of both α-fucose residues, β systems show a certain degree of multiplicity, likely due to diversity in the positions of interglycosidic linkages of sugar residues. β-Anomeric protons appeared as two unresolved multiplets centered at 4.4 and 4.9 ppm, together with signals of protons from sulfation sites, whereas the remaining fucan A protons appear in the range of 3.5–4.5 ppm [16]. Signals around 1.2–1.4 ppm were assigned to CH3 protons of fucose residues.

Figure 2B depicts the 1H NMR of SNFuc. The reaction between fucan and hexadecylamine follows a Michael addition mechanism. Signals between 5.6 and 1.0 ppm in the 1H NMR spectrum of SNFuc are assigned to protons from the fucan A scaffold. Proton peaks from hexadecylamine are observed at 2 ppm and at 1.0–1.3 ppm. These overlap the signals of CH3 groups from fucose residues (Figure 3B) [25]. The proton signal near 3 ppm is attributive to neither the fucan nor the hexadeyilamine and thus it seems to arise from a contaminant that could not be eliminated by extensive 2 dialyses. According to COSY experiment (Figure 3C), this signal does not correlated with those of polysaccharide or substituent.

Figure 3.1H NMR spectra of native fucan (A) and SNFuc in D2O at 25 °C (B) and Correlation Spectroscoy analysis (COSY spectrum) of SNFuc (C).

Figure 3.1H NMR spectra of native fucan (A) and SNFuc in D2O at 25 °C (B) and Correlation Spectroscoy analysis (COSY spectrum) of SNFuc (C).

Due to the overlap of the peaks arising from the fucan and the hexadecylamine protons, it was not possible to determine the degree of substitution (DS) using the 1H NMR spectrum analysis. Nonetheless the 1H NMR spectrum confirms the chemical grafting of hexadecylamine molecule to the fucan structure, as evidenced by the hexadecylamine peaks.

Therefore the degree of substitution (DS) was estimated through the SNFuc elemental analysis, based on the ratio of amide nitrogen and the sulfate sulfur from the fucans. This resulted in a N/S ratio of 0.66 (2.9/4.4). Taking into account the proposed structure of the fucan and the corresponding theoretical elemental composition, a degree of substitution superior to 100% is obtained. Indeed, according to the structure shown in Figure 1, fucan has 14 sulfate groups per 6 carboxylic groups. Thus, if 100% of the carboxylic groups react with an hexadecylamine, we would end up with a ratio of 6N/14S, therefore our experimental N/S ratio corresponds to a degree of substitution above the maximum theoretical value. This may be interpreted as significant of a very high degree of substitution, probably close to 100%, the value obtained being certainly overestimated due to heterogeneity of the fucan; the theoretical structure used in this estimation may not accurately correspond to the material used.

2.3. Formation of Nanoparticles

Dissolution of SNFuc in water is expected to give rise to micelle formation, owing to the amphiphilic nature of the molecule. Nanogel formation was assessed by Dynamic Light Scattering (DLS).

DLS analysis provides valuable information on the homogeneity of dispersion. SNFuc (0.1 g/dL) in aqueous media had a mean diameter of 123 nm, with unimodal size distribution and a corresponding average polydispersity index of 0.269 (Figure 4A). Since size distribution intensity is somewhat influenced by the presence of larger particles, whereas volume distribution better characterizes the more representative population, we also analyzed the volume distribution of nanoparticles. SNFuc volume analysis also demonstrated the homogeneity of nanoparticles (Figure 4B). The observation of the nanogel by CryoSEM provides images of particles in the same size range as detected by DLS (Figure 4D).

Figure 4. Particle size distribution (A) and volume (%) (B) of SNFuc nanogels (0.1 g/dL) measured by dynamic light scattering (DLS) and Fucan nanogels observed by Cryo-SEM (C

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