Photocuring 3D printing technology as an advanced tool for promoting angiogenesis in hypoxia-related diseases

Three-dimensional (3D) bioprinting has emerged as a promising strategy for fabricating complex tissue analogs with intricate architectures, such as vascular networks. Achieving this necessitates bioink formulations that possess highly printable properties and provide a cell-friendly microenvironment mimicking the native extracellular matrix. Rapid advancements in printing techniques continue to expand the capabilities of researchers, enabling them to overcome existing biological barriers. This review offers a comprehensive examination of ultraviolet-based 3D bioprinting, renowned for its exceptional precision compared to other techniques, and explores its applications in inducing angiogenesis across diverse tissue models related to hypoxia. The high-precision and rapid photocuring capabilities of 3D bioprinting are essential for accurately replicating the intricate complexity of vascular networks and extending the diffusion limits for nutrients and gases. Addressing the lack of vascular structure is crucial in hypoxia-related diseases, as it can significantly improve oxygen delivery and overall tissue health. Consequently, high-resolution 3D bioprinting facilitates the creation of vascular structures within three-dimensional engineered tissues, offering a potential solution for addressing hypoxia-related diseases. Emphasis is placed on fundamental components essential for successful 3D bioprinting, including cell types, bioink compositions, and growth factors highlighted in recent studies. The insights provided in this review underscore the promising prospects of leveraging 3D printing technologies for addressing hypoxia-related diseases through the stimulation of angiogenesis, complementing the therapeutic efficacy of cell therapy.

A general photoiniferter approach to the surface functionalization of acrylic and methacrylic structures written by two-photon stereolithography

Two-photon stereolithography (TPS) is an established additive fabrication technique allowing the voxel-by-voxel direct writing of even intricate 3D nano/microstructures via the polymerization of a photoresin. An obvious way to tune the chemical functionalities of such nano/microstructures is formulating a photoresin with the desired functional monomer(s). Unfortunately, this makes every photoresin "unique" in terms of viscosity and reactivity, thus requiring a tedious and often time-consuming optimization of its printing parameters. In this work, we describe a general approach for the chemical functionalization of TPS-written structures based on two commercial photoresins. Our strategy entailed the grafting of functional polymer layers via an innovative approach based on photoiniferter coupling to unreacted double bonds and photopolymerization. After writing woodpiles as 3D model structures, we demonstrated the viability of this approach by anchoring a photoiniferter via its photoinduced addition to the residual CC on the structure's surface triggered by green light. This in turn allowed for the blue light-mediated, surface-initiated photopolymerization of functional monomers. Molecularly imprinted polymer films were also easily synthesized by using the same approach on model honeycombs. The imprinted layers resulted in only a minimal increase in size with no effect on the geometrical features of the honeycombs. Overall, this strategy offers a general approach for the surface modification of TPS-written (meth)acrylic structures with a wide variety of functional polymers via photoiniferter polymerization.

Photoinduced Iron-Catalyzed ATRP of Renewable Monomers in Low-Toxicity Solvents: A Greener Approach

Producing polymers from renewable resources via more sustainable approaches has become increasingly important. Herein we present the polymerization of monomers obtained from biobased renewable resources, employing an environmentally friendly photoinduced iron-catalyzed atom transfer radical polymerization (ATRP) in low-toxicity solvents. We demonstrate that renewable monomers can be successfully polymerized into sustainable polymers with controlled molecular weights and narrow molar mass distributions (Đ as low as 1.17). This is in contrast to reversible addition-fragmentation chain-transfer (RAFT) polymerization, arguably the most commonly employed method to polymerize biobased monomers, which led to poorer molecular weight control and higher dispersities for these specific monomers (Đs ∼ 1.4). The versatility of our approach was further highlighted by the temporal control demonstrated through intermittent "on/off" cycles, controlled polymerizations of a variety of monomers and chain lengths, oxygen-tolerance, and high end-group fidelity exemplified by the synthesis of block copolymers. This work highlights photoinduced iron-catalyzed ATRP as a powerful tool for the synthesis of renewable polymers.

Bioscreening and pre-clinical evaluation of the impact of bioactive molecules from Ptychotis verticillata on the multilineage potential of mesenchymal stromal cells towards immune- and inflammation-mediated diseases

OBJECTIVE AND DESIGN

Mesenchymal stromal cells (MSCs) are currently used in cell reparative medicine due to their trophic and ant-inflammatory properties. The modulation of stem cell properties by phytochemicals has been suggested as a tool to empower their tissue repair capacity. In vitro, MSCs are characterized by their tri-lineage potential that holds great interest for tissue regeneration. Ptychotis Verticillata (PV), an aromatic and medicinal plant, may be thus used to modulate the in vitro multilineage potential of MSCs.

MATERIALS AND METHODS

We screened the impact of PV-derived essential oil and their bioactive molecules (thymol and carvacrol) on the in vitro multilineage potential of MSCs. Different concentrations and incubation times of these compounds were assessed during the osteogenesis and adipogenesis of MSCs.

RESULTS

The analysis of 75 conditions indicates that these compounds are biologically active by promoting two major differentiation lineages from MSCs. In a time- and dose-dependent manner, thymol and carvacrol increased the osteogenesis and adipogenesis.

CONCLUSION

According to these preliminary observations, the addition of PV extract may stimulate the tissue regenerative and repair functions of MSCs. Further optimization of compound extraction and characterization from PV as well as cell treatment conditions should increase their therapeutic value in combination with MSCs.

Antibacterial and cytotoxic properties of star-shaped quaternary ammonium-functionalized polymers with different pendant groups

The correlation between the structure and biological activity of polymers is critically important for rationally designing effective antibacterial polymers. Here, the antibacterial activity, cytotoxicity, and selectivity of structurally well-defined, star-shaped...

Phloroglucinol-enhanced whey protein isolate hydrogels with antimicrobial activity for tissue engineering

Aging populations in developed countries will increase the demand for implantable materials to support tissue regeneration. Whey Protein Isolate (WPI), derived from dairy industry by-products, can be processed into hydrogels with the following desirable properties for applications in tissue engineering: (i) ability to support adhesion and growth of cells; (ii) ease of sterilization by autoclaving and (iii) ease of incorporation of poorly water-soluble drugs with antimicrobial activity, such as phloroglucinol (PG), the fundamental phenolic subunit of marine polyphenols. In this study, WPI hydrogels were enriched with PG at concentrations between 0 and 20% w/v. PG solubilization in WPI hydrogels is far higher than in water. Enrichment with PG did not adversely affect mechanical properties, and endowed antimicrobial activity against a range of bacteria which occur in healthcare-associated infections (HAI). WPI-PG hydrogels supported the growth of, and collagen production by human dental pulp stem cells and - to a lesser extent - of osteosarcoma-derived MG-63 cells. In summary, enrichment of WPI with PG may be a promising strategy to prevent microbial contamination while still promoting stem cell attachment and growth.

Multiphoton Laser Fabrication of Hybrid Photo-Activable Biomaterials

The possibility to shape stimulus-responsive optical polymers, especially hydrogels, by means of laser 3D printing and ablation is fostering a new concept of “smart” micro-devices that can be used for imaging, thermal stimulation, energy transducing and sensing. The composition of these polymeric blends is an essential parameter to tune their properties as actuators and/or sensing platforms and to determine the elasto-mechanical characteristics of the printed hydrogel. In light of the increasing demand for micro-devices for nanomedicine and personalized medicine, interest is growing in the combination of composite and hybrid photo-responsive materials and digital micro-/nano-manufacturing. Existing works have exploited multiphoton laser photo-polymerization to obtain fine 3D microstructures in hydrogels in an additive manufacturing approach or exploited laser ablation of preformed hydrogels to carve 3D cavities. Less often, the two approaches have been combined and active nanomaterials have been embedded in the microstructures. The aim of this review is to give a short overview of the most recent and prominent results in the field of multiphoton laser direct writing of biocompatible hydrogels that embed active nanomaterials not interfering with the writing process and endowing the biocompatible microstructures with physically or chemically activable features such as photothermal activity, chemical swelling and chemical sensing.

Antimicrobial Hybrid Coatings Combining Enhanced Biocidal Activity under Visible-Light Irradiation with Stimuli-Renewable Properties

Hybrid, organic-inorganic, biocidal films exhibiting polishing properties were developed as effective long-lasting antimicrobial surface coatings. The films were prepared using cationically modified chitosan, synthesized by the reaction with 3-bromo-N,N,N-trimethylpropan-1-aminium bromide, to introduce permanent biocidal quaternary ammonium salt (QAS) groups along the polymer backbone and were cross-linked by a novel, pH-cleavable acetal cross-linker, which allowed polishing the hybrid coatings with the solution pH. TiO₂ nanoparticles, modified with reduced graphene oxide (rGO) sheets, to narrow their band gap energy value and shift their photocatalytic activity in the visible light regime, were introduced within the polymer film to enhance its antibacterial activity. The hybrid coatings exhibited an effective biocidal activity in the dark (∼2 Log and ∼3 Log reduction for Gram-negative and Gram-positive bacteria, respectively), when only the QAS sites interacted with the bacteria membrane, and an excellent biocidal action upon visible-light irradiation (∼5 Log and ∼6 Log reduction for Gram-negative and Gram-positive bacteria, respectively) due to the synergistic antimicrobial effect of the QAS moieties and the rGO-modified TiO₂ nanoparticles. The gradual decrease in the film thickness, upon immersion of the coatings in mildly basic (pH 8), neutral (pH 7), and acidic (pH 6) media, reaching 10, 20, and 70% reduction, respectively, after 60 days of immersion time, confirmed the polishing behavior of the films, whereas their effective antimicrobial action was retained. The biocompatibility of the hybrid films was verified in human cell culture studies. The proposed approach enables the facile development of highly functional coatings, combining biocompatibility and bactericidal action with a "kill and self-clean" mechanism that allows the regeneration of the outer surface of the coating leading to a strong and prolonged antimicrobial action.