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A brief history of hollow glass microspheres

2023-01-09 16:52:49 303

Hollow glass microspheres offer numerous functional advantages for biopharmaceuticals. These tiny spherical particles can be derived from a growing range of organic and inorganic materials, making them an extremely versatile solution for novel drug delivery systems.

Further research and development (R&D) into new compositions continues to create new opportunities for microsphere technology deployment.

Researchers have generated porous or hollow glass microspheres to enhance their drug-carrying capacity. Such hollow glass microspheres have been used to protect fragile drug compounds in vivo and to extend their bioavailability. There have also been many strides forward with biodegradable polymer hollow glass microspheres for controlled drug delivery. The growing availability of highly tunable microspheres has significant ramifications for treating numerous conditions, including embolisation therapy, lipoatrophy in AIDS patients, stress urinary incontinence (SUI) treatment), and so on. Microsphere technology is also of growing importance in precision medicine and targeted therapies for cancer and cardiovascular disease.

The future of microsphere technology is bright. But where did the use of spherical shape particles with microscopic size ranges originate?

Hollow Glass Microspheres – Small Particles on the Big Screen

The IUPAC defines a microsphere as a “microparticle of spherical shape without membrane of any distinct outer layer”, with a note that quality, sphericity, uniformity, particle size, and particle size distribution (PSD) vary wildly. Microscopic glass beads produced in New York in 1914 are perhaps the earliest example of synthetically produced particles which would fit that description. By 1922, enormous quantities of hollow glass microspheres with high refractive indices were commissioned to produce movie screen coatings.

Hollow glass microspheres were developed as an offshoot of these glass beads during the ‘50s. Sometimes described as micro-balloons or glass bubbles, these hollow particles offered a significantly reduced density to solid glass microspheres, combined with enhanced functionality. This initiated the rapid growth and acceleration of microsphere technology. During the ‘60s, hollow glass microspheres were used as fillers for the booming plastics industry.

Today, ceramic microspheres are available for industrial applications, improving composite thermosets’ durability, strength, and toughness. Some ceramic microspheres even serve biomedical applications, such as minimally invasive implantation and bone defect filling. Likewise, glass-based microspheres have been used in pharmaceuticals, specifically as novel delivery systems for biodegradable radiation.

Hollow Glass Microspheres – Pharmaceutical Applications

However, ceramic and glass microspheres have limited applicability to the pharmaceutical sector compared with natural and synthetic polymers. Hollow glass microspheres composed of biocompatible polymers have a tightly controlled, uniform shape and size, demonstrated by predictable behaviour when injected. This opens up numerous avenues of application for in vivo clinical use of polymeric hollow glass microspheres . Although the scope of application is ever-growing, clinical use of polymer hollow glass microspheres can largely be broken down into one of three areas. They are used: in fillers and bulking agents to replace lost tissue volume; as embolic particles; and as drug delivery vehicles.

Modern Microsphere Innovations

Continual refinement of the technologies underlying how hollow glass microspheres are made has enabled a new generation of biomedical-grade solutions. Manufacturers can now develop various systems based on synthetic biopolymers, ceramics, and bioactive glasses. The geometries of these particles can also be finely tuned, as can the porosity, to improve mass density and surface area greatly. Alongside the apparent drug absorption and release kinetics that this entails, tailoring particles enhances their interconnectivity and allows for the assembly of three-dimensional porous scaffolds. The biomedical applications of hollow glass microspheres , therefore, are extremely broad in scope.