Microparticles (MPs) derived from acid-sensitive biopolymers enable rapid degradation and cargo release under acidic conditions, such as at tumor microenvironments, within lysosomal/phagosomal compartments inside phagocytic cells, or at sites of inflammation. One such acid-sensitive biopolymer, acetalated dextran (Ace-DEX), has tunable degradation rates and pH-neutral degradation byproducts consisting of dextran, acetone, and ethanol. By studying the degradation profiles of Ace-DEX MPs with varying cyclic acetal coverage (CAC) and dextran molecular weight (MW), we concluded that MPs composed of low CAC or high MW polymer degraded the fastest at both pH 7.4 and 5.0. To further understand the properties of this unique polymer, we encapsulated a model drug resiquimod, which is a toll-like receptor (TLR) 7/8 agonist, into Ace-DEX MPs of different polymer CAC and dextran MW. It was observed that resiquimod was released faster from MPs of lower CAC or higher MW. By evaluating the activation of RAW macrophages cultured with different types of resiquimod-loaded Ace-DEX MPs, we found that MPs of lower CAC or higher MW promoted greater nitrite production and resulted in more robust cell activation. Our results indicate we can precisely control the degradation profile, release kinetics, and bioactivity of encapsulated cargos by altering CAC and MW, furthering Ace-DEX MPs' novelty as a drug carrier.

Almond anthracnose was reported for the first time in Australia in 1998 and has since been observed in all of the major almond-growing regions. The organism causing anthracnose was confirmed as Colletotrichum acutatum using taxon-specific polymerase chain reaction (PCR). Three main morphotypes of C. acutatum from almond in Australia were identified (namely, pink, orange, and cream colony color) and the optimum temperature for mycelial growth of representative isolates was 25 degrees C. Australian isolates of C. acutatum were more similar morphologically to the pink subpopulation of C. acutatum from California than to the gray Californian subpopulation and the isolates of Colletotrichum from Israel. Inter-simple-sequence-repeat (ISSR) PCR analysis revealed that the majority of Australian isolates shared an identical banding pattern whereas Australian isolates of C. acutatum from almond were distinct from isolates of the pink and gray subpopulations of C. acutatum from almond in California and of Colletotrichum spp. from almond in Israel. Sequence analysis of the internally transcribed spacer (ITS1-2) ribosomal DNA region of representative isolates differed from the results of ISSR-PCR in that polymorphisms were revealed among isolates, indicating that some genetic variation may be present. Pathogenicity experiments on detached leaves and fruit revealed pathogenic variation among representative isolates of C. acutatum from almond in Australia, California, and Israel; however, all isolates tested caused disease. Distinct subgroups among Australian isolates of C. acutatum from almond were not supported on the basis of morphology, mycelial growth rates, ISSR-PCR, and pathogenicity.

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