Chinese Academy of Sciences successfully developed degradable glass

glass a sustainable material?

Its raw materials are rich natural resources, such as limestone (calcium oxide), soda ash (sodium carbonate) and quartz sand (silicon dioxide); it can be recycled for unlimited times and 100% utilization; compared with plastic, which is the product of petroleum, its production process and waste have much less impact on the environment.

But the sheer demand creates environmental problems that cannot be ignored: sand mining destroys the sandbanks where fish, birds and seals live; sand dredging shrinks beaches and even causes bridges to collapse; kilns consume energy and emit greenhouse gases; and glass, because of its weight, takes more energy to transport than plastic; In fact, how much glass is actually recycled.. and it takes millions of years for glass to decompose in nature.

Cold, hard, and requiring a high-temperature manufacturing process, the properties of glass may make it difficult to associate it with biomaterials. Recently, however, Yan Xuehai, a researcher at the Institute of Process Engineering, Chinese Academy of Sciences, published the Biomolecular glass with amino acid and peptide in

Science Advances

. Nanoarchitectonics, reported that biodegradable glass can also be made using amino acids and peptides.

Amino acids and peptides are abundant biomolecules in organisms and have been widely used to develop functional nanostructured materials. This environmentally friendly material can be recycled in the ecosystem. But its nature is far from that of glass.

Glass is an amorphous solid that is formed by heating at a high temperature above its melting temperature (Tm) and then rapidly cooling (quenching), as sufficiently rapid cooling prevents crystal formation. However, natural amino acids and peptides have poor thermal stability and are easily decomposed into amines and carbon dioxide at high temperatures near Tm. Therefore, glass cannot be made directly from these natural biomolecules.

Previous studies have shown that amino acids and peptides can significantly improve their thermal stability when chemically modified with hydrophobic groups at the end. Inspired by this, researchers began to modify amino acids and peptides.

To avoid molecular breakdown, the researchers used Ac-, Fmoc-, and Cbz- groups to chemically modify a range of amino acids and peptides. After heating, randomly selected natural amino acids, including glutamine (Q), histidine (H), phenylalanine (F), and tyrosine (Y), were found to lose more than 15% in weight, while valine (V) and leucine (L) were completely decomposed, losing more than 90% at a temperature of Tm.

The results show that the Tm values of these modified molecules are much lower than decomposition temperature. The successful melting of biomolecular compounds before decomposition is undoubtedly a breakthrough in the preparation of biomolecular glasses.

Next, these modified amino acids and peptides successfully formed biomolecular glasses by performing a procedural heating and quenching procedure in inert gas with a heating and cooling rate of 10 K/min. The glass forming ability (GFA) and properties of biomolecular glasses, including the kinetic and thermodynamic parameters associated with the glass transition, were subsequently evaluated. Transmission spectra

in the ultraviolet (UV) to visible (200 to 800 nm) and near infrared (NIR) (800 to 3000 nm) regions show that these glasses exhibit good optical properties (about 90% transmission), Better than glass used in common commercial lighting applications (average 80%). In combination with carbon quantum dots (CQDs) and dyes, biomolecules can also form a series of fluorescent colored glasses.

▲ Figure | Transmission spectra of glass in the UV-visible region (left) and the near-infrared region (right) (Source: [1])

▲ Figure | Excited by UV light with a wavelength of 365 nm, Glasses fluoresce differently (Source: [1])

The biomolecular glass also has good mechanical properties and flexible processability. The researchers printed the "CAS" with a commercial bio-3D printer, using a specific mold to obtain a series of shapes of glass.

(Source: [1])

To determine whether biomolecular glass is environmentally friendly, the researchers conducted in vitro and in vivo biodegradation experiments and composting experiments. The above results show that the glass not only has biodegradability, but also shows excellent biocompatibility and biosafety in mice.