PDITC

Figure 7.25 The multivalent nature of dendrimers can be used to add increased functionality to surfaces. Aminopropyl silane surfaces can be activated with either PDITC or through use of a cyclic anhydride plus DCC/ NHS to give amine-reactive surfaces. These reactive surfaces can be used to couple amine-dendrimers to provide a high density of amine groups on the surface for further bioconjugation.

Enzyme Conjugation to Diamine-Modified DNA Using PDITC... 

Dissolve lOmg of PDITC (Aldrich) in 500pi of DMF. Add this solution to the oligo prepared in step 1. 

Figure 27.16 The homobifunctional crosslinker PDITC may be used to conjugate an enzyme to a 5 -diamine-modified oligonucleotide, creating isothiourea linkages.

Fig. 8 Covalent attachment of amine-terminated oligonucleotides to amino-modified (APS) supports via a PDITC linker...

To extract excess reactant, add to the reaction medium, 3 ml of w-butanol and 3 ml of water. Mix well. Centrifuge the mixture to separate the two phases. Discard the upper yellow layer. Repeat the extraction process several times, then dry the remaining solution containing activated oligo using a lyophilizer or a rotary evaporator. The PDITC-activated DNA is stable in a dry state. 

PAMAM]. The final step of this functionalization relied on activation and cross-linking of attached dendrimers with a homobifunctional spacer (DSG or PDITC). Alternatively, after attachment of dendrimers to the surface, glutaric anhydride activated with V-h ydrox vsucc i n i m i de can be used. This surface modification yields a thin, chemically reactive polymer film, which is covalently attached to the glass support and can be directly used for the covalent attachment of amino-modified components, such as DNA or peptides (Fig. 14.2b). 

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