Antimicrobial Activity of Ca-Alginate/Chitosan Nanocomposite Loaded with Camptothecin

The main aim of this study was to prepare antimicrobial nanocomposites consisting of alginate, chitosan, and camptothecin (CPT). CPT-loaded calcium alginate (Ca-Alg₂) and calcium alginate/chitosan (Ca-Alg₂-CH) nanomaterials were synthesized and characterized using infrared (IR) spectroscopy, X-ray diffraction (XRD), UV-Vis spectroscopy, and scanning electron microscopy (SEM). The antimicrobial activity and the genetic effects of Ca-Alg₂/CPT and Ca-Alg₂-CH/CPT nanomaterials on Staphylococcus aureus, Escherichia coli, and Klebsiella pneumonia were studied. The repetitive element polymerase chain reaction analysis technique was used to assess the changes in the bacterial genetic material due to the processing of the nanomaterials. The results showed the presence of a strong chemical interaction between alginate and chitosan, and CPT was loaded successfully in both Ca-Alg₂/CPT and Ca-Alg₂-CH/CPT nanomaterials. Furthermore, the antimicrobial test showed that the Ca-Alg₂/CPT nanocomposite was susceptible to S. aureus, E. coli, and K. pneumonia; on the other hand, Ca-Alg₂-CH/CPT nanocomposite was more susceptible to E. coli and K. pneumonia and was resistant to S. aureus. The results showed that the Ca-Alg₂/CPT nanocomposite was less efficient than Ca-Alg₂-CH/CPT nanocomposite in killing Gram-negative treated bacteria. Moreover, results revealed that the PCR analysis revealed a polymorphic banding pattern. This observation provides an excellent guide to the ability of some polymers to induce point mutations in DNA.

A delivery system for field application of paratransgenic control

BACKGROUND

As an alternative to chemical pesticides, paratransgenesis relies on transformation of symbiotic bacteria of an arthropod vector to deliver molecules that disrupt pathogen transmission. For over a decade paratransgenesis has remained a laboratory-based endeavor owing to regulatory concerns regarding introduction of transformed microorganisms into the environment. To facilitate field application of paratransgenic strategies, risk mitigation approaches that address environmental contamination and gene spread must be developed.

RESULTS

Using biopolymer manipulation, we introduce a novel microencapsulation platform for containment and targeted delivery of engineered bacteria to the gut of a disease-transmitting arthropod. We demonstrate the first proof of principle of targeted delivery of EPA-approved Pantoea agglomerans E325 in a paratransgenic system to control spread of Pierce's Disease by glassy-winged sharpshooters, (Homalodisca vitripennis) under simulated field conditions. Engineered microcapsules may address regulatory concerns regarding containment of recombinant bacteria and environmental spread of foreign genetic material and may represent an important step in translating paratransgenic science beyond the lab and into the field.

CONCLUSIONS

We present, for the first time, a microencapsulation strategy to deliver recombinant bacteria to an insect and demonstrate targeted release of bacteria into the physiologically relevant region of the insect gut. This is a first step toward addressing concerns related to field application of recombinant bacteria. Engineered microparticles may decrease environmental contamination, horizontal gene transfer and competition with native species by acting as a barrier between recombinant bacteria and the environment.