Multifunctional Surface Modification: Facile and Flexible Reactivity toward a Precisely Controlled Biointerface.

A multicomponent functional polymer is synthesized to support specific reactivity for successful conjugation with the vast array of functionality present in biological systems and the flexibility to conjugate biomolecules without requiring additional modification to install a terminal functional group. The multifunctional surface is realized using a novel coating composed of distinct N-hydroxysuccinimide (NHS) ester and benzoyl functionalities, which can provide accessibility to both the NHS ester-amine coupling reaction and the photochemically induced benzophenone crosslinking reaction, respectively. In addition, the multifunctional polymer is fabricated and transformed to form nanoscale colloids through the solvent displacement of a water/DMF system due to solubility characteristics of the resulting polymer with high polarity. A facile and efficient fabrication approach using the multifunctional nanocolloid is thus demonstrated to create a drug carrier by installing paclitaxel and folic acid for targeted cancer therapy.

Fabrication of multipotent poly-para-xylylene particles in controlled nanoscopic dimensions.

In this study, poly-para-xylylene-based multifunctional nanoparticles (PPX-NPs) were fabricated. Based on the solubility characteristics determined for asymmetrically substituted poly-para-xylylenes in polar solvents, well-dispersed nanocolloids with a controllable size ranging from 50 to 800nm were produced in solution by the displacement of the solvent (water). These size ranges were found to have acceptable cellular compatibility through examinations of cultured 3T3 fibroblasts and adipose-derived stem cells treated with the PPX-NPs. In addition, these nanoscale PPX-NPs exhibited versatile bioconjugation properties in that a variety of available functional groups can be adopted from their counterpart, thin-film poly-para-xylylenes, during the production of these nanoparticles. For instance, bifunctional PPX-NPs with maleimide and benzoyl moieties were produced to enable immobilization via a maleimide-thiol reaction concurrent with a photochemical reaction. A cleavable PPX-NP was also produced with a thiol-exchangeable surface property. Additionally, by performing electrohydrodynamic jetting of parallel polymer solutions of selected poly-para-xylylenes, Janus-type or multicompartment PPX-NPs were created. The PPX-NPs can potentially be used for various biomedical applications such as combined diagnostics and drug delivery, multiplexing of detection, multiple-drug loading, and the targeted delivery of biomolecules or drugs.

Switching the Biointerface of Displaceable Poly-p-xylylene Coatings.

A new class of functionalized poly-p-xylyene coating has been synthesized to provide switchable and displaceable surface properties for biomaterials. The switchability is achieved through a mechanism for detaching/attaching biomolecules and/or a mechanism through which the programmed restoration of functions or their replacement by other functions can be carried out. This advanced version of poly-p-xylylene comprises an integrated disulfide moiety within the functional side group, and the switching phenomenon between the immobilized functional molecules is triggered by the redox thiol-disulfide interchange reaction. These dynamically well-defined molecules on the surfaces respond simultaneously to altered biological properties and controlled biointerfacial functions, for example, switching wettability or reversibly altered cell adhesion activity. Poly-p-xylylenes are a key player in controlling surface properties for many important applications, such as medical implants, biosensors, bioMEMS devices, and microfluidics. The introduction of this new facet of poly-p-xylylenes enables the dynamic mimicry of biological functions relevant to the design of new biomaterials.