Designing Liquid-Infused Surfaces for Medical Applications: A Review.

The development of new technologies is key to the continued improvement of medicine, relying on comprehensive materials design strategies that can integrate advanced therapeutic and diagnostic functions with a variety of surface properties such as selective adhesion, dynamic responsiveness, and optical/mechanical tunability. Liquid-infused surfaces have recently come to the forefront as a unique approach to surface coatings that can resist adhesion of a wide range of contaminants on medical devices. Furthermore, these surfaces are proving highly versatile in enabling the integration of established medical surface treatments alongside the antifouling capabilities, such as drug release or biomolecule organization. Here, the range of research being conducted on liquid-infused surfaces for medical applications is presented, from an understanding of the basics behind the interactions of physiological fluids, microbes, and mammalian cells with liquid layers to current applications of these materials in point-of-care diagnostics, medical tubing, instruments, implants, and tissue engineering. Throughout this exploration, the design parameters of liquid-infused surfaces and how they can be adapted and tuned to particular applications are discussed, while identifying how the range of controllable factors offered by liquid-infused surfaces can be used to enable completely new and dynamic approaches to materials and devices for human health.

Preventing mussel adhesion using lubricant-infused materials.

Mussels are opportunistic macrofouling organisms that can attach to most immersed solid surfaces, leading to serious economic and ecological consequences for the maritime and aquaculture industries. We demonstrate that lubricant-infused coatings exhibit very low preferential mussel attachment and ultralow adhesive strengths under both controlled laboratory conditions and in marine field studies. Detailed investigations across multiple length scales-from the molecular-scale characterization of deposited adhesive proteins to nanoscale contact mechanics to macroscale live observations-suggest that lubricant infusion considerably reduces fouling by deceiving the mechanosensing ability of mussels, deterring secretion of adhesive threads, and decreasing the molecular work of adhesion. Our study demonstrates that lubricant infusion represents an effective strategy to mitigate marine biofouling and provides insights into the physical mechanisms underlying adhesion prevention.

Transparent antifouling material for improved operative field visibility in endoscopy.

Camera-guided instruments, such as endoscopes, have become an essential component of contemporary medicine. The 15-20 million endoscopies performed every year in the United States alone demonstrate the tremendous impact of this technology. However, doctors heavily rely on the visual feedback provided by the endoscope camera, which is routinely compromised when body fluids and fogging occlude the lens, requiring lengthy cleaning procedures that include irrigation, tissue rubbing, suction, and even temporary removal of the endoscope for external cleaning. Bronchoscopies are especially affected because they are performed on delicate tissue, in high-humidity environments with exposure to extremely adhesive biological fluids such as mucus and blood. Here, we present a repellent, liquid-infused coating on an endoscope lens capable of preventing vision loss after repeated submersions in blood and mucus. The material properties of the coating, including conformability, mechanical adhesion, transparency, oil type, and biocompatibility, were optimized in comprehensive in vitro and ex vivo studies. Extensive bronchoscopy procedures performed in vivo on porcine lungs showed significantly reduced fouling, resulting in either unnecessary or ∼10-15 times shorter and less intensive lens clearing procedures compared with an untreated endoscope. We believe that the material developed in this study opens up opportunities in the design of next-generation endoscopes that will improve visual field, display unprecedented antibacterial and antifouling properties, reduce the duration of the procedure, and enable visualization of currently unreachable parts of the body, thus offering enormous potential for disease diagnosis and treatment.

A colloidoscope of colloid-based porous materials and their uses.

Nature evolved a variety of hierarchical structures that produce sophisticated functions. Inspired by these natural materials, colloidal self-assembly provides a convenient way to produce structures from simple building blocks with a variety of complex functions beyond those found in nature. In particular, colloid-based porous materials (CBPM) can be made from a wide variety of materials. The internal structure of CBPM also has several key attributes, namely porosity on a sub-micrometer length scale, interconnectivity of these pores, and a controllable degree of order. The combination of structure and composition allow CBPM to attain properties important for modern applications such as photonic inks, colorimetric sensors, self-cleaning surfaces, water purification systems, or batteries. This review summarizes recent developments in the field of CBPM, including principles for their design, fabrication, and applications, with a particular focus on structural features and materials' properties that enable these applications. We begin with a short introduction to the wide variety of patterns that can be generated by colloidal self-assembly and templating processes. We then discuss different applications of such structures, focusing on optics, wetting, sensing, catalysis, and electrodes. Different fields of applications require different properties, yet the modularity of the assembly process of CBPM provides a high degree of tunability and tailorability in composition and structure. We examine the significance of properties such as structure, composition, and degree of order on the materials' functions and use, as well as trends in and future directions for the development of CBPM.

Pulsed ultrasound enhances nanoparticle penetration into breast cancer spheroids.

Effective treatment of solid tumors requires homogeneous distribution of anticancer drugs within the entire tumor volume to deliver lethal concentrations to resistant cancer cells and tumor-initiating cancer stem cells. However, penetration of small molecular weight chemotherapeutic agents and drug-loaded polymeric and lipid particles into the hypoxic and necrotic regions of solid tumors remains a significant challenge. This article reports the results of pulsed ultrasound enhanced penetration of nanosized fluorescent particles into MCF-7 breast cancer spheroids (300-350 µm diameter) as a function of particle size and charge. With pulsed ultrasound application in the presence of microbubbles, small (20 nm) particles achieve 6-20-fold higher penetration and concentration in the spheroid's core compared to those not exposed to ultrasound. Increase in particle size to 40 and 100 nm results in their effective penetration into the spheroid's core to 9- and 3-fold, respectively. In addition, anionic carboxylate particles achieved higher penetration (2.3-, 3.7-, and 4.7-fold) into the core of MCF-7 breast cancer spheroids compared to neutral (2.2-, 1.9-, and 2.4-fold) and cationic particles (1.5-, 1.4-, and 1.9-fold) upon US exposure for 30, 60, and 90 s under the same experimental conditions. These results demonstrate the feasibility of utilizing pulsed ultrasound to increase the penetration of nanosized particles into MCF-7 spheroids mimicking tumor tissue. The effects of particle properties on the penetration enhancement were also illustrated.