Srinivas Banala

A fine-tuned dimethylamino-fluorenyl core with substituents at the C9-position to improve SWIR fluorescence emissions.

Highly reactive oxygen and nitrogen species (ROS/RNS) play crucial roles in various pathological conditions. Among them, hypochlorous ion (OCl⁻), a potent ROS, is associated in numerous oxidative stress‐related disorders. Elevated levels of OCl⁻ are thus recognized as a biomarker for diagnosing inflammatory conditions. To enable selective detection of OCl⁻ via photoacoustic (PA) imaging, we present development of a near infrared(NIR)‐absorbing BODIPY‐based acoustogenic probe. Four regioisomers of methoxyphenols‐conjugated BODIPYs were synthesized to investigate the positional influence on OCl⁻ selectivity over other ROS/RNS. Our study reveals that only one isomer, 4‐methoxy phenol conjugation, exhibited exceptional selectivity for OCl⁻ without any competitive reactions, making it suitable for PA imaging. This study highlights the importance of regioisomers characterization in achieving intricate selectivity among competing reactive species. The fine‐tuning and development of a suitable dye now enable the optimization of physicochemical properties for in vivo OCl⁻ detection using PA imaging.

During the COVID‐19 pandemic, the use of polypropylene fleece‐based personal protection equipment (PPE) increased significantly to over ten million tons. Typically, most PPEs are discarded after a single use, to prevent self‐infection of users and spread of infectious agents. However, in order to minimize plastic waste without compromising the protective properties of PPE, it is crucial to explore new reusable or longer‐lived materials. Here, a visible light‐activatable antimicrobial photodynamic dye coating for PPEs is presented. In this context, coating with thiomorpholino‐methylene blue (TMB), derived from methylene blue by introducing two thiomorpholine units, is found to show high antibacterial activity. TMB is integrated into rotary printing suspension, a commercial nitrocellulose‐based printing matrix. The concentration of TMB in adhesive is optimized, and found that 5% TMB is suitable for coating PPE, for reducing the number of Gram‐positive and ‐negative bacteria by 99.99% after 6 h of white light irradiation. Bacterial filtration efficiency and breathability tested according to EN 14683, confirmed that TMB coating does not affect the filter performance. Thus, this antimicrobial photodynamic dye coating technique offers a promising solution for a safer and extended use of PPE, and reduction of plastic waste generated by PPEs.

The isolation and characterization of a kinetically stable oxadiazaborinine (ODB) dye are described, which undergoes an unexpected thermal boron rearrangement with a color change and increase in fluorescence. This controllable reaction allows for the use as a practical time‐temperature indicator probe with the advantages of photostability, non‐reversibility, and environmental friendliness.

Short-lived reactive intermediates such as reactive oxygen species (ROS) regulate many physiological processes, but overproduction can also lead to severe tissue dysfunction. Thus, there is a high demand for noninvasive detection of reactive molecules, which, however, is challenging. Herein, we report photoacoustic detection of ROS using conjugated BODIPY probes (ROS-BODIPYs). The ROS reaction with conjugated BODIPYs induced a redshift in absorption by ∼100 nm into the near infrared (from ∼700 to ∼800 nm), quenched fluorescence, and generated strong photoacoustic (PA) signals. Thus, the ROS-activated and ROS-nonactivated states of ROS-BODIPYs can be detected in vivo by PA and fluorescence imaging. Interestingly, ROS activation is reversible, in the presence of excess reducing agents, e.g., citric acid, converted back to its original state, suggesting that ROS-BODIPYs can be useful for the detection of over production of ROS but not physiological amounts. This makes the imaging independent of accumulation of the activated probe with the physiological ROS amounts and thus strongly improves applicability and highlights the translational potential of ROS-BODIPYs for detecting overexpression of ROS in vivo by optical and photoacoustic imaging methods.

Cold‐chain management is of high importance in preserving perishable products and in retaining quality. A visible marker on packages indicating complete maintenance of the cold chain assures safe consumption of products by end‐users and assists in reducing waste. Time‐temperature indicators (TTIs) are integrated markers that provide information about exposure of packages to adverse temperature and have been gaining increased attention by consumers. Here we present a methylene‐blue‐based derivative, N,N,N′,N′‐tetramethyl‐N¹⁰‐Boc‐phenothiazine‐3,7‐diamine (BocPTDA), that can be used as a solid‐state organic TTI dye, exhibiting an irreversible change from colorless to blue green upon heating. The conversion properties, studied using a silicagel‐coated plate, confirmed that BocPTDA undergoes a color change above 20 °C. At temperatures of 4 °C and below, no visible changes are exhibited, making BocPTDA a well‐suited marker for monitoring abrupt temperature deviations indicating improper cold‐chain management. Thus, application of BocPTDA‐based TTI systems on packages could inform consumers about the cold‐chain maintenance, assuring quality and safe consumption.

We report a systematic tuning of optical properties of BODIPY dyes by conjugation of nitrogen-rich heterocycles, and underlying nitrogen influence by TDDFT calculations.

A broad spectrum ROS/RNS sensing butylated phenol tethered leucomethylene blue is presented. This probe detects a variety of ROS/RNS, with up to 100-fold gain in fluorescence in the red range, is suitable for microscopic and macroscopicin vivofluorescence imaging.

Photoacoustic imaging (PAI) is a rapidly evolving field in molecular imaging that enables imaging in the depths of ultrasound and with the sensitivity of optical modalities. PAI bases on the photoexcitation of a chromophore, which converts the absorbed light into thermal energy, causing an acoustic pressure wave that can be captured with ultrasound transducers, in generating an image. For in vivo imaging, chromophores strongly absorbing in the near-infrared range (NIR; > 680 nm) are required. As tetrapyrroles have a long history in biomedical applications, novel tetrapyrroles and inspired mimics have been pursued as potentially suitable contrast agents for PAI. The goal of this review is to summarize the current state of the art in PAI applications using tetrapyrroles and related macrocycles inspired by it, highlighting those compounds exhibiting strong NIR-absorption. Furthermore, we discuss the current developments of other absorbers for in vivo photoacoustic (PA) applications.