Effects of pH on the Morphological Structures and Release Properties in Chitosan Microspheres

With an attempt to expand the versatilities and applications in chitosan microspheres, distinct morphological structures and properties of chitosan microspheres were produced by treating with various pH values of Na
₅
P
₃
O
₁₀
/NaOH solution reagents, also under various volume ratio of these solution (17/3, 19/1, pure Na
₅
P
₃
O
₁₀
or pure NaOH solution). The prepared chitosan microsphere had a good spherical shape and was in a range of 185.8±13.8 μm to 380.9±11.5 μm in diameter. When pH values decreased from initially pH 12 (except in case for pure Na
₅
P
₃
O
₁₀
where the pH being 8.8) to pH 7, the chitosan microspheres size varied, and reached a maximum diameter after treatment with pH 7 of these reaction agents. The prepared chitosan microspheres upon treatment with pH 7 of various ratios Na
₅
P
₃
O
₁₀
/NaOH solution, all exhibited a shrunken surface morphological structure. This densely shrunken structure of microspheres yielded a stronger mechanical strength and a slower release rate of drug (5-FU), no matter what the ratios of Na
₅
P
₃
O
₁₀
/NaOH solution was used. From the data of FTIR analyses, the protonated amino peak of NH
₃
⁺
at around 1562 cm
^-1
has decreased significantly. It could be attributed to the crosslinking reaction between phosphoric and ammonium ion of the chitosan microspheres.