Methylene Blue-Loaded Upconverting Hydrogel Nanocomposite: Potential Material for Near-Infrared Light-Triggered Photodynamic Therapy Application

The property of upconverting nanoparticles to convert the low-energy near-infrared (NIR) light into high-energy visible light has made them a potential candidate for various biomedical applications including photodynamic therapy (PDT). In this work, we show how a surface functionalization approach on the nanoparticle can be used to develop a nanocomposite hydrogel which can be of potential use for the PDT application. The upconverting hydrogel nanocomposite was synthesized by reacting 10-undecenoic acid-capped Yb3+/Er3+-doped NaYF4 nanoparticles with the thermosensitive N-isopropylacrylamide monomer. The formation of hydrogel was completed within 15 min and hydrogel nanocomposites showed strong enhancement in the visible light emission compared to the emission obtained from 10-undecenoic acid-capped Yb3+/Er3+-doped NaYF4 nanoparticles via the upconversion process (under 980 nm laser excitation). The upconverting hydrogel nanocomposites displayed high swelling behavior in water because of their porous nature. The porous structure ensured a higher loading of methylene blue dye (∼78% in 1 h) into the upconverting hydrogel, which was achieved via the swelling diffusion phenomenon. Upon excitation with the NIR light, the visible light emitted from the hydrogel activated the photosensitizer methylene blue which generated reactive oxygen species. Our results were able to show that the methylene blue-loaded composite hydrogel can be a potential platform for the future of NIR-triggered PDT in skin cancer treatment.

Nucleobase-Containing Polymers: Structure, Synthesis, and Applications

Nucleobase interactions play a fundamental role in biological functions, including transcription and translation. Natural nucleic acids like DNA are also widely implemented in material realm such as DNA guided self-assembly of nanomaterials. Inspired by that, polymer chemists have contributed phenomenal endeavors to mimic both the structures and functions of natural nucleic acids in synthetic polymers. Similar sequence-dependent responses were observed and employed in the self-assembly of these nucleobase-containing polymers. Here, the structures, synthetic approaches, and applications of nucleobase-containing polymers are highlighted and a brief look is taken at the future development of these polymers.

Manufacturing of hydrogel biomaterials with controlled mechanical properties for tissue engineering applications

Hydrogels have been recognized as crucial biomaterials in the field of tissue engineering, regenerative medicine, and drug delivery applications due to their specific characteristics. These biomaterials benefit from retaining a large amount of water, effective mass transfer, similarity to natural tissues and the ability to form different shapes. However, having relatively poor mechanical properties is a limiting factor associated with hydrogel biomaterials. Controlling the biomechanical properties of hydrogels is of paramount importance. In this work, firstly, mechanical characteristics of hydrogels and methods employed for characterizing these properties are explored. Subsequently, the most common approaches used for tuning mechanical properties of hydrogels including but are not limited to, interpenetrating polymer networks, nanocomposites, self-assembly techniques, and co-polymerization are discussed. The performance of different techniques used for tuning biomechanical properties of hydrogels is further compared. Such techniques involve lithography techniques for replication of tissues with complex mechanical profiles; microfluidic techniques applicable for generating gradients of mechanical properties in hydrogel biomaterials for engineering complex human tissues like intervertebral discs, osteochondral tissues, blood vessels and skin layers; and electrospinning techniques for synthesis of hybrid hydrogels and highly ordered fibers with tunable mechanical and biological properties. We finally discuss future perspectives and challenges for controlling biomimetic hydrogel materials possessing proper biomechanical properties.

STATEMENT OF SIGNIFICANCE

Hydrogels biomaterials are essential constituting components of engineered tissues with the applications in regenerative medicine and drug delivery. The mechanical properties of hydrogels play crucial roles in regulating the interactions between cells and extracellular matrix and directing the cells phenotype and genotype. Despite significant advances in developing methods and techniques with the ability of tuning the biomechanical properties of hydrogels, there are still challenges regarding the synthesis of hydrogels with complex mechanical profiles as well as limitations in vascularization and patterning of complex structures of natural tissues which barricade the production of sophisticated organs. Therefore, in addition to a review on advanced methods and techniques for measuring a variety of different biomechanical characteristics of hydrogels, the new techniques for enhancing the biomechanics of hydrogels are presented. It is expected that this review will profit future works for regulating the biomechanical properties of hydrogel biomaterials to satisfy the demands of a variety of different human tissues.

Double bond terminated Ln3+-doped LiYF4 nanocrystals with strong single band NIR emission: simple click chemistry route to make water dispersible nanocrystals with various functional groups

A simple thiol–ene click chemistry strategy to develop upconverting nanocrystals with different functional groups.