The aggregation behavior of four samples of hydrophobically modified hyaluronan was examined in water and in 0.15 M NaCl. The samples differed in the length of their hydrocarbon modifying chains, degree of substitution, or hyaluronan molecular weight. The critical aggregation concentration was determined by fluorescence spectroscopy using pyrene as a probe. Aggregation was observed even with hyaluronan modified by a short alkyl chain (C6). The critical aggregation concentration decreased with increasing alkyl chain length and with increasing hyaluronan molecular weight at a comparable degree of substitution. Aggregation was detected over a rather broad concentration interval, indicating a progressive formation of aggregates. Two populations of aggregates were detected for the oleyl substitution. The addition of NaCl had only minor effect on the critical aggregation concentration.
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