This Special Issue on Surface Modification contains twenty‐five papers addressing various aspects of surface modification. This issue grew out of several symposia on particle‐based drug and gene delivery held at the international conference Particles 2002 in Orlando, Florida during April 20–23, 2002, wherein surface modification is important in targeting specific tissues and cell types and in accommodating DNA. This issue focuses on surface modification of particles, generally in the submicron size range, but it also addresses some key aspects of planar surface modification. The issue is divided into two parts: the first part contains reviews and the second part contains research papers. Each part begins with surface modification papers dealing with other than drug or gene delivery and ends with the papers derived from the Particles 2002 (http://nanoparticles.org) conference.
The review section begins with a very nice update on recent developments in soft lithography by Brehmer, Conrad, and Funk. These new methods are becoming increasingly important in self‐assembly processing and in pushing the envelope in developing alternatives to high energy lithography. This paper is followed by a nearly exhaustive review of plasma treatment of polymers by Grace and Gerenser of the Eastman Kodak Company, where arguably more surface area has its surface energy “adjusted” by physical and chemical means than possibly at any other site. The rest of the reviews are particle focused, and Advincula's review on surface initiated polymerization provides excellent current insight into methods for passivating nanoparticles. A review of clay and related particle surface modification follows by van Oss and Giese, where a focus on controlling surface energetics through additives is presented. Shchukin and Ameina provide an excellent discussion of how surface modification by various adsorption processes affects contact interactions between particles and surfaces. This and the preceding paper provide a very physical analysis of surface modification. Papers from Garti's group at the Casali Institute and from Kunieda's laboratory provide insight into the role of additives of various types in modifying interfacial surfaces in single phase microemulsion systems.
The transition into drug and gene delivery commences with a thorough review from Pichot and co‐workers on various useful approaches to functionalizing latex particles. These approaches are complemented by Lambert's review on gene delivery using particle surface complexation and particle encapsulation approaches. Bagwe and Tan provide a concise review of how to make luminescent nanoparticles useful for various applications by use of microemulsion technology and bioconjugation. MacKay and Szoka then provide a very current perspective of how to deliver nanoparticles into cells using transcriptional activator proteins. Jung‐Hyun Kim's group provides a broad perspective on diverse approaches to surface‐functionalized nanoparticles, and they also provide details on diverse approaches to the activation chemistry, including surface reactive micelles for targeting. The last review from Cho's laboratory covers the use and modification of chitosan in gene delivery.
The second section on research papers begins with an excellent description from Moudgil's laboratory of particle/slurry optimization for chemical mechanical polishing applications. This is followed by a thorough description of using metal ion adsorption to control surface forces, from Vithayaverok, Yiacoumi, and Tsouris. A somewhat indirect examination of surface charge modification through metal ion adsorption is provided from Xu's laboratory, where the effects of continuous phase ligands on metal ion binding are examined with respect to titania zeta potentials. The use of ATR‐FTIR in examining interparticle crosslinking is given by Kim and co‐workers. Zhao et al. demonstrate how planar surfaces may be modified to produce analytical tools, such as a fluorescent detection methods for sodium ion. HRTEM and electron diffraction are used to give an excellent description of the preparation and characterization of carbon‐coated nanoparticles by Sun.
The drug and gene delivery research papers of this second section commence with a very extensive paper from Mumper's group on using microemulsion technology to make diverse classes of nanoparticles and subsequently engineering surface functionalization for cell targeting. Bringley and Liebert present an orthogonal picture of novel new chemical approaches to drug (and other chemical) delivery, utilizing a diverse range of layered materials that have yet to be extensively exploited. Li and co‐workers give a very nice description of the preparation of core‐shell latexes with PMMA cores and amino‐modified polymeric shells. The important use of magnetic particles and their surface modification with antibody–antigen chemistry is illustrated by Santana. Sakuma and a lengthy list of co‐workers demonstrate the optimization of particles and surface modification for oral delivery. Finally, Wang and collaborators present an interesting approach to plasmid delivery by using amine‐modified silica particles.
These papers span a range of topics and particularly illustrate the burgeoning importance of particle technology and surface modification chemistry in drug delivery, gene therapy, and biochemical diagnostics. The critical importance of surface modification in many other applications continues, and both synthetic and physical perspectives are given in this special issue.
John Texter
Editor‐in‐Chief