Spatial variation in the macrobenthic assemblages of intertidal seagrass along the long axis of an estuary
- Authors: Barnes, R S K , Ellwood, M D F
- Date: 2014-05-29
- Language: English
- Type: Article
- Identifier: vital:6870 , http://hdl.handle.net/10962/d1011513
- Description: Invertebrate macrofaunal biodiversity within intertidal seagrass meadows was investigated over a salinity gradient of <5–35 in the Knysna estuarine system (Garden Route National Park, South Africa). Rather than the classic gradual decline in species richness with distance from the mouth there were zones of considerable faunal stability separated by relatively sharp discontinuities. At the point upstream at which salinity regularly falls below 30, the rich, diverse and highly spatially variable downstream faunal assemblage changed to a less rich, less diverse and more uniform one that dominated the upstream stretch without any further upstream reduction in richness. Nevertheless, without loss of overall richness, assemblage composition changed, again rapidly, in the upper region of the upstream stretch to a zone dominated by the microgastropod Hydrobia, which otherwise occurs in the Knysna system only in highly sheltered regions of the downstream stretch where it is also dominant. The upstream faunal assemblage was a subset of that in the marine-influenced downstream region not a different replacing one. Position along the estuarine gradient accounted for 29% of total assemblage variation. Overall faunal abundance declined with distance upstream until the Hydrobia zone where it rose sharply, but there was no evidence of increase in density of those species remaining on putative release from competition.
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(Dis)allowances of lesbians’ sexual identities: Lesbian identity construction in racialised, classed, familial, and institutional spaces
- Authors: Gibson, Alexandra , Macleod, Catriona I
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6222 , http://hdl.handle.net/10962/d1006536 , http://dx.doi.org/10.1177/0959353512459580
- Description: This article explores how lesbian identity construction is facilitated and constrained by the raced, classed, gendered, familial, and geographical spaces that women occupy. We present a narrative-discursive analysis of eight lesbians’ stories of sexuality, told within a historically white university in South Africa. Three interpretative repertoires that emerged in the narratives are discussed. The ‘disallowance of lesbian identity in particular racialised and class-based spaces’ repertoire, deployed by black lesbians only, was used to account for their de-emphasis of a lesbian identity through the invocation of a threat of danger and stereotyping. The ‘disjuncture of the (heterosexual) family and lesbian identity’ repertoire emphasised how the expectation of support and care within a family does not necessarily extend to acceptance of a lesbian identity.
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- Date Issued: 2012
A quantitative post-release evaluation of biological control of water lettuce, Pistia stratiotes L. (Araceae) by the weevil Neohydronomus affinis Hustache (Coleoptera: Curculionidae) at Cape Recife Nature Reserve, Eastern Cape Province, South Africa
- Authors: Moore, Gareth R , Hill, Martin P
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6839 , http://hdl.handle.net/10962/d1010987 , http://dx.doi.org/10.4001/003.020.0217 , https://orcid.org/0000-0003-0579-5298
- Description: [from the introduction] Water lettuce, Pistia stratiotes L. (Araceae) is recognized as being among the world’s worst aquatic weeds. In its adventive range, the plant forms extensive mats capable of blocking navigation channels, impeding water flow in irrigation and flood control canals, and disrupting hydropower generation (Holm et al. 1977). Dense mats of the weed prevent light penetration into the water column which negatively affects submerged aquatic plant communities, causing a lowering of the oxygen concentration and thereby reducing benthic invertebrate and fish populations (Neuenschwander et al. 2009).
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- Date Issued: 2012
An ion-imprinted polymer for the selective extraction of mercury(II) ions in aqueous media
- Authors: Batlokwa, Bareki Shima , Chimuka, Luke , Tshentu, Zenixole R , Cukrowska, Ewa , Torto, Nelson
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6566 , http://hdl.handle.net/10962/d1004125
- Description: A double-imprinted polymer exhibiting high sensitivity for mercury(II) in aqueous solution is presented. Polymer particles imprinted with mercury(II) were synthesised by copolymerising the functional and cross-linking monomers, N’–[3– (Trimethoxysilyl)–propyl]diethylenetriamine (TPET) and tetraethylorthosilicate (TEOS). A double-imprinting procedure employing hexadecyltrimethylammonium bromide (CTAB), as a second template to improve the efficiency of the polymer, was adopted. The imprinted polymer was characterised by FTIR, scanning electron microscopy (SEM) and the average size determined by screen analysis using standard test sieves. Relative selective coefficients (k`) of the imprinted polymer evaluated from selective binding studies between Hg2+ and Cu2+ or Hg2+ and Cd2+ were 10 588 and 3 147, respectively. These values indicated highly-favoured Hg2+ extractions over the 2 competing ions. The results of spiked and real water samples showed high extraction efficiencies of Hg2+ ions, (over 84%) as evaluated from the detected unextracted Hg2+ ions by ICP-OES. The method exhibited a dynamic response concentration range for Hg2+ between 0.01 and 20 μg/mℓ, with a detection limit (LOD, 3σ) of 0.000036 μg/mℓ (36 ng/ℓ) that meets the monitoring requirements for the USA EPA of 2 000 ng/ℓ for Hg2+ in drinking water. Generally, the data (n=10) had percentage relative standard deviations (%RSD) of less than 4%. Satisfactory results were also obtained when the prepared sorbent was applied for the pre-concentration of Hg2+ from an aqueous certified reference material. These findings indicate that the double-imprinted polymer has potential to be used as an efficient extraction material for the selective pre–concentration of mercury(II) ions in aqueous environments.
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- Date Issued: 2012
Anatomy of a pottery bonfiring in the Port St Johns region, Eastern Cape, South Africa
- Authors: Steele, John
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/11260/1034 , vital:30232
- Description: This paper seeks to document and contextualise the unique bonfiring methods of octogenarian potter Alice Gqa Nongebeza, who works from her homestead at Nkonxeni village in the Tombo area near Port St Johns. Her firing technique is compared with those of fellow local potters Debora Nomathamsanqa Ntloya and Nontwazana Dunjana. These three Mpondo potters, and their understudies, create ceramic utilityware and other items for a mainly local market that sometimes also appeals to collectors and tourists. Although they are aware of each other, they use their own clay sources and clayworking methods, and have evolved very different firing techniques. This paper, with reference also to potters in KwaZulu-Natal, shows that Nongebeza, in particular, has developed a rare approach to firing, and calls for the inclusion of her type of firing technique in African firing lexicons. It also calls for greater attention to sequential firing detail as practised by individual potters, in forthcoming reports that add to knowledge about zeroelectricity- usage ceramics production in southern Africa, and elsewhere.
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- Date Issued: 2012
Changing sediment yield and sediment dynamics in the Karoo uplands, South Africa : post-European impacts
- Authors: Foster, I D L , Rowntree, Kate M , Boardman, J , Mighall, T M
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6684 , http://hdl.handle.net/10962/d1006683
- Description: We provide an overview of published results and a significant body of new data from an ongoing research programme designed to reconstruct sediment yields and sources in small (<60 km2) catchments in the Eastern Cape, South Africa over the last 150 years. Our analysis of four catchments has determined that sediment yield increased significantly in the latter half of the 20th Century but that the exact timing of these increases was different in each of the four catchments. In two high altitude locations, sediment yield increases were not associated with a significant change in sediment source, although in one case areas of former cultivation appear to have made a slightly greater contribution since the 1960s. In a third catchment, increases in sediment yield appear to have been driven by the development of badlands and by an increase in connectivity between the badlands and the main channel network in the 1960s. In the fourth catchment, increased connectivity between the main catchment and dam occurred as a result of the construction of a causeway to carry a main road and by the construction of culverts beneath the road. Occasional changes in sediment source have also been identified in the sedimentary record but these were not linked directly to road construction. Research to date shows the complexity of sediment delivery in these semi-arid catchment systems and emphasises the need to combine sediment yield with source ascription in order to better understand the dynamics of these systems.
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- Date Issued: 2012
Contrasting habitat associations of imperilled endemic stream fishes from a global biodiversity hot spot
- Authors: Chakona, Albert , Swartz, Ernst R
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:7148 , http://hdl.handle.net/10962/d1011850 , http://www.biomedcentral.com/1472-6785/12/19
- Description: Knowledge of the factors that drive species distributions provides a fundamental baseline for several areas of research including biogeography, phylogeography and biodiversity conservation. Data from 148 minimally disturbed sites across a large drainage system in the Cape Floristic Region of South Africa were used to test the hypothesis that stream fishes have similar responses to environmental determinants of species distribution. Two complementary statistical approaches, boosted regression trees and hierarchical partitioning, were used to model the responses of four fish species to 11 environmental predictors, and to quantify the independent explanatory power of each predictor.
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- Date Issued: 2012
Cooperative wasp-killing by mixed-species colonies of honeybees, Apis cerana and Apis mellifera
- Authors: Tan, K , Yang, M-Y , Li, H , Zhang, Z-L , Radloff, Sarah E , Hepburn, H Randall
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6838 , http://hdl.handle.net/10962/d1010979 , http://dx.doi.org/10.1007/s13592-011-0098-5
- Description: The cooperative defensive behaviour of mixed-species colonies of honeybees, Apis cerana and Apis mellifera, were tested against a predatory wasp, Vespa velutina. When vespine wasps hawk honeybees at their nest entrances, the difference in the numbers of bees involved in heat-balling among pure species and mixed-species colonies was not significantly different. However, in the mixed colonies, the numbers of A. cerana and A. mellifera workers involved in heat-balling were significantly different. The duration of heat-balling among these three groups was significantly different. During heat-balling, guard bees of both species in mixed colonies raised their thoracic temperatures and the core temperatures of the heat-balls were about 45°C, which is not significantly different from that of the pure species. These results suggest that the two species of honeybees can cooperate in joint heat-balling against the wasps, but A. cerana was more assertive in such defence.
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- Date Issued: 2012
Cryptic variation in an ecological indicator organism: mitochondrial and nuclear DNA sequence data confirm distinct lineages of Baetis harrisoni Barnard (Ephemeroptera: Baetidae) in southern Africa
- Authors: Pereira-da-Conceicoa, L L , Price, Benjamin W , Barber-James, Helen M
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:7151 , http://hdl.handle.net/10962/d1011855
- Description: Baetis harrisoni Barnard is a mayfly frequently encountered in river studies across Africa, but the external morphological features used for identifying nymphs have been observed to vary subtly between different geographic locations. It has been associated with a wide range of ecological conditions, including pH extremes of pH 2.9–10.0 in polluted waters. We present a molecular study of the genetic variation within B. harrisoni across 21 rivers in its distribution range in southern Africa.
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- Date Issued: 2012
Cryptic variation in an ecological indicator organism: mitochondrial and nuclear DNA sequence data confirm distinct lineages of Baetis harrisoni Barnard (Ephemeroptera: Baetidae) in Southern Africa
- Authors: Pereira-da-Conceicoa, Lyndall L , Price, Benjamin W , Barber-James, Helen M , Barker, Nigel P , de Moor, Ferdy C , Villet, Martin H
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6535 , http://hdl.handle.net/10962/d1005976 , https://dx.doi.org/10.1186/1471-2148-12-26
- Description: Baetis harrisoni Barnard is a mayfly frequently encountered in river studies across Africa, but the external morphological features used for identifying nymphs have been observed to vary subtly between different geographic locations. It has been associated with a wide range of ecological conditions, including pH extremes of pH 2.9–10.0 in polluted waters. We present a molecular study of the genetic variation within B. harrisoni across 21 rivers in its distribution range in southern Africa.
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- Date Issued: 2012
Dynamics of a lattice Universe : the dust approximation in cosmology
- Authors: Bruneton, J-P , Larena, Julien
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6789 , http://hdl.handle.net/10962/d1006941
- Description: We find a solution to Einstein field equations for a regular toroidal lattice of size L with equal masses M at the centre of each cell; this solution is exact at order M/L. Such a solution is convenient to study the dynamics of an assembly of galaxy-like objects. We find that the solution is expanding (or contracting) in exactly the same way as the solution of a Friedman–Lemaître–Robertson–Walker Universe with dust having the same average density as our model. This points towards the absence of backreaction in a Universe filled with an infinite number of objects, and this validates the fluid approximation, as far as dynamics is concerned, and at the level of approximation considered in this work.
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- Date Issued: 2012
Effects of patch-size on populations of intertidal limpets, Siphonaria spp., in a linear landscape
- Authors: Cole, Victoria J , Johnson, Linda G , McQuaid, Christopher D
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6845 , http://hdl.handle.net/10962/d1011050
- Description: Organisms with different life-histories and abilities to disperse often utilise habitat patches in different ways. We investigated the influence of the size of patches of rock (separated by stretches of sand) on the density of pulmonate limpets (Siphonaria spp.) along 1500 km of the linear landscape of the South African coastline. We compared the influence of patch-size on two congeneric species with different modes of development, S. serrata a direct developer, and S. concinna a planktonic developer. We tested the spatial and temporal consistency of the effects of patch-size by sampling 7 independent regions spanning the distributional range of both species of limpets, and by sampling one region at monthly intervals for 1 year. Within each region or month, 4 small patches (<20 m in length) interspersed with the 4 large patches (>60 m in length) were sampled. Across the entire geographic range and throughout the year, there were more of both species of limpets in large patches than in small patches. In most regions, there was greater variability in large patches than small patches. Variability within patches in a single region was similar throughout the year, with greater variability of both species in large than in small patches. We found little influence of the mode of development on the response of limpets to patch-size. Our findings highlight the importance of understanding patterns of distribution of species with respect to habitat heterogeneity in linear landscapes, and contradict the idea that organism mobility at an early ontogenetic stage directly affects habitat use.
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- Date Issued: 2012
Evaluation of a service-learning elective as an approach to enhancing the pharmacist's role in health promotion in South Africa
- Authors: Srinivas, Sunitha C , Wrench, Wendy W
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6443 , http://hdl.handle.net/10962/d1006630
- Description: Background. A service-learning (SL) elective offered to final-year pharmacy students was introduced in 2007. The elective demonstrated a holistic approach to creating opportunities for future pharmacists to understand the current needs and future challenges of the burden of disease in developing countries such as South Africa and to foresee their key roles in health promotion. Methods. The 2007 Sasol National Festival of Science and Technology (SciFest) was chosen as the ideal platform to implement this elective. Evaluation of the elective was carried out in association with the Academic Development Centre using a web-based software tool known as the ADC evaluation assistant (ADCEA). The ADCEA consisted of a ‘question bank’ from which the course facilitators selected nine ranked closed questions as well as two open-ended questions. Results. SciFest participation, in the course of the service-learning elective, was acknowledged by students to have prepared them as responsible citizens to undertake health promotion in the public sector healthcare system. Conclusion. Students’ experiences of the learning opportunities provided in the SciFest elective highlight the strengths of this SL programme.
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- Date Issued: 2012
From the grave to the cradle : the possibility of post-mortem gamete retrieval and reproduction in South Africa
- Authors: Kruuse, Helen
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:24533 , http://hdl.handle.net/10962/36254 , http://www.tandfonline.com/doi/abs/10.1080/19962126.2012.11865059
- Description: The development of reproductive technologies in the last century, such as effective contraceptive methods, artificial insemination, pre-implantation genetic diagnosis, amongst others, has fundamentally reshaped traditional concepts of reproduction parenthood and has raised practical and ethical concerns. This article describes one such development, namely, post-mortem gamete retrieval (PMGR) for the purposes of posthumous reproduction. In exploring the particular concerns arising from this technology, I argue that South Africa lacks a coherent, considered approach to the issue. In considering models adopted in overseas jurisdictions, and the various bases for the legalisation of such a procedure, I adopt an interest theory of rights to argue for restricted access to such a technology in suitable circumstances.
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- Date Issued: 2012
Gravitational entropy and thermodynamics away from the horizon
- Authors: Brustein, R , Medved, A J M
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6818 , http://hdl.handle.net/10962/d1004328
- Description: We define, by an integral of geometric quantities over a spherical shell of arbitrary radius, an invariant gravitational entropy. This definition relies on defining a gravitational energy and pressure, and it reduces at the horizon of both black branes and black holes to Wald's Noether charge entropy. We support the thermodynamic interpretation of the proposed entropy by showing that, for some cases, the field theory duals of the entropy, energy and pressure are the same as the corresponding quantities in the field theory. In this context, the Einstein equations are equivalent to the field theory thermodynamic relation TdS=dE+PdV supplemented by an equation of state
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- Date Issued: 2012
Graviton n-point functions for UV-complete theories in Anti-de Sitter space
- Authors: Brustein, R , Medved, A J M
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6820 , http://hdl.handle.net/10962/d1004427
- Description: We calculate graviton n-point functions in an anti-de Sitter black brane background for effective gravity theories whose linearized equations of motion have at most two time derivatives. We compare the n-point functions in Einstein gravity to those in theories whose leading correction is quadratic in the Riemann tensor. The comparison is made for any number of gravitons and for all physical graviton modes in a kinematic region for which the leading correction can significantly modify the Einstein result. We find that the n-point functions of Einstein gravity depend on at most a single angle, whereas those of the corrected theories may depend on two angles. For the four-point functions, Einstein gravity exhibits linear dependence on the Mandelstam variable s versus a quadratic dependence on s for the corrected theory.
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- Date Issued: 2012
In vitro dissolution kinetics of Captopril from microspheres manufactured by solvent evaporation
- Authors: Khamanga, Sandile M , Walker, Roderick B
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6390 , http://hdl.handle.net/10962/d1006311
- Description: The aim of this study was to develop and assess captopril-loaded microspheres in which Methocel and Eudragit RS were used as release-controlling factors and to evaluate captopril (CPT) release using kinetic models. Drug-excipient interactions were evaluated using infrared studies, and the physical appearance was characterized using scanning electron microscopy (SEM). A burst effect was observed during the first stage of dissolution for most batches of microspheres. SEM results reveal that this may be attributed to dissolution of captopril crystals that were present on the surface, embedded in the superficial layer of the matrix materials, trapped near the surface of the microspheres, or that may have diffused rapidly through the porous surface of the capsules. The release data generated during in vitro release studies were fitted to zero-order, first-order, Higuchi, Korsmeyer–Peppas, Kopcha, and Makoid–Banakar models. The release kinetics of captopril from most formulations followed a classical Fickian diffusion mechanism. SEM photographs showed that diffusion took place through pores located in the surface of the microcapsules. The Kopcha model diffusion and erosion terms showed a predominance of diffusion relative to swelling or erosion throughout the entire test period. The drug release mechanism was also confirmed by the Makoid–Banakar and Korsmeyer–Peppas model exponents. This further supports a diffusion–release mechanism for most formulations. The models postulate that the total drug released is a summation of several mechanisms (viz., burst release, relaxation-induced controlled release, and diffusional release). These results also support the potential application of Eudragit/Methocel microspheres as a suitable sustained-release drug delivery system for captopril.
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- Date Issued: 2012
Investigating the nature of epistemological access afforded by a first-year chemistry intervention programme : towards a pedagogy of possibility!
- Authors: Southwood, Sue , Samson, Duncan , Sewry, Joyce D
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6083 , http://hdl.handle.net/10962/d1003918 , http://hdl.handle.net/10520/EJC132134
- Description: This paper describes a study motivated by a general concern to capture innovative and effective practice in higher education, supporting a move towards a ‘pedagogy of possibility’, ‘understanding who we are and what we do’, opening up ‘new ways of being in the university’ (Boughey, 2010). The research seeks to investigate the nature of epistemological access afforded by a first-year chemistry intervention programme, with an ultimate aim of contributing to the development of effective spaces for learning in higher education. The study is regarded as dynamic in terms of its emergence from, and its intended contribution to, practice. The outcome of this somewhat emergent process not only suggests relevant and useful insights into educational practice in higher education but also offers an appropriate and meaningful model for conducting research in higher education. This research contributes to the field both pedagogically as well as methodologically.
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- Date Issued: 2012
Large pollen loads of a South African asclepiad do not interfere with the foraging behaviour or efficiency of pollinating honey bees
- Authors: Coombs, Gareth , Dold, Anthony P , Brassine, Eleanor I , Peter, Craig I
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6509 , http://hdl.handle.net/10962/d1005936
- Description: The pollen of asclepiads (Asclepiadoideae, Apocynaceae) and most orchids (Orchidaceae) are packaged as large aggregations known as pollinaria that are removed as entire units by pollinators. In some instances, individual pollinators may accumulate large loads of these pollinaria. We found that the primary pollinator of Cynanchum ellipticum (Apocynaceae-Asclepiadoideae), the honey bee Apis mellifera, accumulate very large agglomerations of pollinaria on their mouthparts when foraging on this species. We tested whether large pollinarium loads negatively affected the foraging behaviour and foraging efficiency of honey bees by slowing foraging speeds or causing honey bees to visit fewer flowers, and found no evidence to suggest that large pollinarium loads altered foraging behaviour. C. ellipticum displayed consistently high levels of pollination success and pollen transfer efficiency (PTE). This may be a consequence of efficiently loading large numbers of pollinaria onto pollinators even when primary points of attachment on pollinators are already occupied and doing so in a manner that does not impact the foraging behaviour of pollinating insects.
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- Date Issued: 2012
Like a bolt from the blue : phthalocyanines in biomedical optics
- Authors: Sekkat, N , Van den Berg, H , Nyokong, Tebello , Lange, N
- Date: 2012
- Subjects: Biomedical optics Fluorescence diagnosis Phthalocyanines NIR dyes Photodynamic therapy
- Language: English
- Type: Article
- Identifier: vital:6597 , http://hdl.handle.net/10962/d1004346 , http://dx.doi.org/10.3390/molecules17010098
- Description: The purpose of this review is to compile preclinical and clinical results on phthalocyanines (Pcs) as photosensitizers (PS) for Photodynamic Therapy (PDT) and contrast agents for fluorescence imaging. Indeed, Pcs are excellent candidates in these fields due to their strong absorbance in the NIR region and high chemical and photo-stability. In particular, this is mostly relevant for their in vivo activation in deeper tissular regions. However, most Pcs present two major limitations, i.e., a strong tendency to aggregate and a low water-solubility. In order to overcome these issues, both chemical tuning and pharmaceutical formulation combined with tumor targeting strategies were applied. These aspects will be developed in this review for the most extensively studied Pcs during the last 25 years, i.e., aluminium-, zinc- and silicon-based Pcs.
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- Date Issued: 2012