All-optical switching in dye-doped DNA nanofibers

Electrospun composite nanofibers of deoxyribonucleic acid and polylactic acid for skincare applications

The development of useful biomaterials has resulted in significant advances in various fields of science and technology. The demand for new biomaterial designs and manufacturing techniques continues to grow, with the goal of building a sustainable society. In this study, two types of DNA-cationic surfactant complexes were synthesized using commercially available deoxyribonucleic acid from herring sperm DNA (hsDNA, <50 bp) and deoxyribonucleic acid from salmon testes DNA (stDNA, ~2000 bp). The DNA-surfactant complexes were blended with a polylactic acid (PLA) biopolymer and electrospun to obtain nanofibers, and then copper nanoparticles were synthesized on nanofibrous webs. Scanning electron microscopic images showed that all nanofibers possessed uniform morphology. Interestingly, different diameters were observed depending on the base pairs in the DNA complex. Transmission electron microscopy showed uniform growth of copper nanoparticles on the nanofibers. Fourier-transform infrared spectroscopy spectra confirmed the uniform blending of both types of DNA complexes in PLA. Both stDNA- and hsDNA-derived nanofibers showed greater biocompatibility than native PLA nanofibers. Furthermore, they exerted significant antibacterial activity in the presence of copper nanoparticles. This study demonstrates that DNA is a potentially useful material to generate electrospun nanofibrous webs for use in biomedical sciences and technologies.

A Modified Oxazolone Dye Dedicated to Spectroscopy and Optoelectronics

Here we present a newly synthesized bifunctional organic chromophore with appealing spectroscopic and nonlinear optical features. The positions of absorption and emission maxima of the dye vary with increasing solvent polarity and exhibit positive solvatochromism. The determined change in the dipole moment upon excitation based on the Bilot and Kawski theory is 5.94 D, which corresponds to the intermolecular displacement of a charge equal to 1.24 Å. An investigated organic-based system represents a significant, repeatable, and stable over time optical signal modulation in the manner of the refractive index value. Its magnitude is varied both by optical pumping intensity as well as by external frequency modulation, which indicates that such system is an alluring and alternative core unit for optoelectronic devices and complex networks. Then, the same active system, due to the nonresonant mechanism of higher harmonics of light inducement, can provide second and third harmonic signals. According to the introduced laser line spatial modifications (parallel or perpendicular polarization directions), it is resulted in output SHG signal with magnitude varied about 100%. Its magnitude is noticeably small; however, to construct sensitive optical sensors or infrared indicators, such feature may guarantee satisfying circumstances.

Multifunctional Oxazolone Derivative as an Optical Amplifier, Generator, and Modulator

An optical control of many working optoelectronic systems (real-time sensors, optical modulators, light amplifiers, or phase retarders) giving efficient optical gain or remote signal modulation is currently included as scientifically and industrially interesting. In here, an oxazolone derivative as the multifunctional organic system is given in this contribution. The molecule possesses a stilbene group and an oxazolone heteroatomic ring, which implies effective refractive index manipulation and multimode lasing action, respectively. The light modulation is repeatable and stable, also in the hundreds of Hz regime. On the other hand, the amplified optical signal can be easily generated by an external optical pumping source. Thus, signal control is fully available, as is read-in and read-out of the information in real time. Furthermore, this third-order, nonlinear, optical phenomenon using a third harmonic generation technique was also observed. We discovered that only by changing the energy and time regime of the supplied optical signal is the optical or nonlinear optical response observed. Two heteroenergetic molecular states (trans (E) and cis (Z)) can efficiently operate in modern multifunctional optoelectronic systems, which can provide and generate an optical signal. Such functionalities are commonly used in all-optical photonic switchers and logic gates and can be utilized in optical-core networks and computers.

Self-Assembled Biophotonic Lasing Network Driven by Amyloid Fibrils in Microcavities

Self-assembled biological structures have played a significant role in many living systems for its functionality and distinctiveness. Here, we experimentally demonstrate that the random dynamic behavior of strong light-matter interactions in complex biological structures can provide hidden information on optical coupling in a network. The concept of biophotonic lasing network is therefore introduced, where a self-assembled human amyloid fibril network was confined in a Fabry-Perot optical cavity. Distinctive lasing patterns were discovered from self-assembled amyloids with different structural dimensions (0D, 1D, 2D, and 3D) confined in a microcavity. Network laser emission exhibiting evidence of light coupling at different wavelengths and locations was spectrally resolved. Dynamic changes of lasing patterns can therefore be interpreted into a graph to reveal the optical correlation in biophotonic networks. Our findings indicate that each graph represents the highly unclonable features of a self-assembled network which can sensitively respond to environmental stimulus. This study offers the potential for studying dynamic biological networks through amplified interactions, shedding light on the development of biologically controlled photonic devices, biosensing, and information encryption.

Advances in Fabricating the Electrospun Biopolymer-Based Biomaterials

Biopolymers formed into a fibrous morphology through electrospinning are of increasing interest in the field of biomedicine due to their intrinsic biocompatibility and biodegradability and their ability to be biomimetic to various fibrous structures present in animal tissues. However, their mechanical properties are often unsatisfactory and their processing may be troublesome. Thus, extensive research interest is focused on improving these qualities. This review article presents the selection of the recent advances in techniques aimed to improve the electrospinnability of various biopolymers (polysaccharides, polynucleotides, peptides, and phospholipids). The electrospinning of single materials, and the variety of co-polymers, with and without additives, is covered. Additionally, various crosslinking strategies are presented. Examples of cytocompatibility, biocompatibility, and antimicrobial properties are analyzed. Special attention is given to whey protein isolate as an example of a novel, promising, green material with good potential in the field of biomedicine. This review ends with a brief summary and outlook for the biomedical applicability of electrospinnable biopolymers.

DNA Self-Switchable Microlaser

Advances in switchable microlasers have emerged as a building block with immense potential in controlling light-matter interactions and integrated photonics. Compared to artificially designed interfaces, a stimuli-responsive biointerface enables a higher level of functionalities and versatile ways of tailoring optical responses at the nanoscale. However, switching laser emission with biological recognition has yet to be addressed, particularly with reversibility and wavelength tunability over a broad spectral range. Here we demonstrate a self-switchable laser exploiting the biointerface between label-free DNA molecules and dye-doped liquid crystal matrix in a Fabry-Perot microcavity. Laser emission switching among different wavelengths was achieved by utilizing DNA conformation changes as the switching power, which alters the orientation of the liquid crystals. Our findings demonstrate that different concentrations of single-stranded DNA lead to different temporal switching of lasing wavelengths and intensities. The lasing wavelength could be reverted upon binding with the complementary sequence through DNA hybridization process. Both experimental and theoretical studies revealed that absorption strength is the key mechanism accounting for the laser shifting behavior. This study represents a milestone in achieving a biologically controlled laser, shedding light on the development of programmable photonic devices at the sub-nanoscale by exploiting the complexity and self-recognition of biomolecules.

Photoactivated Refractive Index Anisotropy in Fluorescent Thiophene Derivatives

The optical control of anisotropy in materials is highly advantageous for many technological applications, including the real-time modulation of another light signal in photonic switches and sensors. Here, we introduce three thiophene derivatives with a donor-acceptor structure, which feature different positions of an electron-acceptor nitrile group, and both photoalignment and luminescence properties. Quantum chemical calculations highlight the presence of trans-forms stable at room temperature and metastable cis-isomers. Besides photoluminescence peaked at 440-460 nm and 0.4 ns lifetime, the three nonlinear optical chromophores exhibit photoinduced anisotropy of the refractive index closely depending on the specific molecular structure, with higher values of birefringence at lower driving signal being obtained for ortho substitution of the nitrile group. All-optical modulation of an external light beam at rates of hundreds of hertz is demonstrated in the fluorescent systems. This finding opens an interesting route to multispectral photonic switches embedded in the active layers of light-emitting devices.

Dye Stabilization and Wavelength Tunability in Lasing Fibers Based on DNA

Lasers based on biological materials are attracting an increasing interest in view of their use in integrated and transient photonics. Deoxyribonucleic acid (DNA) as optical biopolymer in combination with highly emissive dyes has been reported to have excellent potential in this respect. However, achieving miniaturized lasing systems based on solid-state DNA shaped in different geometries to confine and enhance emission is still a challenge, and the physicochemical mechanisms originating fluorescence enhancement are not fully understood. Herein, a class of wavelength-tunable lasers based on DNA nanofibers is demonstrated, for which optical properties are highly controlled through the system morphology. A synergistic effect is highlighted at the basis of lasing action. Through a quantum chemical investigation, it is shown that the interaction of DNA with the encapsulated dye leads to hindered twisting and suppressed channels for the nonradiative decay. This is combined with effective waveguiding, optical gain, and tailored mode confinement to promote morphologically controlled lasing in DNA-based nanofibers. The results establish design rules for the development of bright and tunable nanolasers and optical networks based on DNA nanostructures.

High-Speed All-Optical Modulator Based on a Polymer Nanofiber Bragg Grating Printed by Femtosecond Laser

On-chip optical modulator for high-speed information processing system has been widely investigated by many researchers, but the connection with the fiber system is difficult. The fiber-based optical modulator is a good solution to this problem. Fiber Bragg Grating has good potential to be used as an optical modulator because of its linear temperature response, narrow bandwidth, and compact structure. In this paper, a new fiber-integrated all-optical modulator has been realized based on a polymer nanofiber Bragg grating printed by a femtosecond laser. This device exhibits a fast temporal response of 176 ns and a good linear modulation of -45.43 pm/mW. Moreover, its stability has also been studied. This work first employs Bragg resonance to realize a fiber-integrated all-optical modulator and paves the way toward realization of multifunctional lab-in-fiber devices.

Advanced Evanescent-Wave Optical Biosensors for the Detection of Nucleic Acids: An Analytic Perspective

Evanescent-wave optical biosensors have become an attractive alternative for the screening of nucleic acids in the clinical context. They possess highly sensitive transducers able to perform detection of a wide range of nucleic acid-based biomarkers without the need of any label or marker. These optical biosensor platforms are very versatile, allowing the incorporation of an almost limitless range of biorecognition probes precisely and robustly adhered to the sensor surface by covalent surface chemistry approaches. In addition, their application can be further enhanced by their combination with different processes, thanks to their integration with complex and automated microfluidic systems, facilitating the development of multiplexed and user-friendly platforms. The objective of this work is to provide a comprehensive synopsis of cutting-edge analytical strategies based on these label-free optical biosensors able to deal with the drawbacks related to DNA and RNA detection, from single point mutations assays and epigenetic alterations, to bacterial infections. Several plasmonic and silicon photonic-based biosensors are described together with their most recent applications in this area. We also identify and analyse the main challenges faced when attempting to harness this technology and how several innovative approaches introduced in the last years manage those issues, including the use of new biorecognition probes, surface functionalization approaches, signal amplification and enhancement strategies, as well as, sophisticated microfluidic solutions.