Photoacoustic monitoring of angiogenesis predicts response to therapy in healing wounds

Optically pH-Sensing in smart wound dressings towards real-time monitoring of wound states: A review

BACKGROUND

Over the recent years, the investigations on wound dressings have been undergoing significant evolution, and now smart dressings with the function of the real-time monitoring of the wound states have been recognized as one of the most advanced treatment modalities. Among a variety of wound-related biomarkers, pH represents a promising candidate for in situ supervising the wound healing status. In this regard, a variety of optically pH sensing agents have been widely incorporated into different types of wound dressings.

RESULTS

Herein, we first presented an overview of the advanced wound dressings, especially those commonly used in wound pH sensing. Then, a comprehensive summary of the optical pH sensing agents that could be incorporated into the wound dressings for detecting the pH alteration on the wound bed was described in detail. These materials were classified into colorimetric dyes (i.e., synthetic and plant-based dyes) and fluorescent probes (i.e., small-molecular fluorescein and fluorescent nanomaterials). Each type of pH sensing agent was fully discussed with advantages and limitations for monitoring the wound pH alteration, as well as typical examples of practical applications. To well interpret messages produced by the color-coding dressings, the approaches for defining and communicating color were also summarized, and a proof-of-concept, the smartphone-based remote supervision was particularly highlighted.

SIGNIFICANCE

This review provides a comprehensive overview of the utilization of optically pH sensing in advanced wound dressings for the real-time monitoring of the wound states. It was expected to be an informative source for the exploitation of novel diagnostic dressings for wound management, and also a reference the for application of these materials in the biosensing of other physiological or pathological fluids.

Influence of Infrared Thermography Predictors in Dental Implant Osteotomies: An Ex Vivo Study

OBJECTIVE

To evaluated the contribution of irrigation, drill type, motor, and dental implant system on infrared thermographic variations in osteotomies.

METHODS

Osteotomy sites for 240 implants were prepared with three implant systems (Arcys, NeoBiotech and Osstem), with 80 samples analyzed in each group. Each group was further subdivided according to the drilling conditions (with and without irrigation) and motor type (Coxo, W&H, Dentflex, Driller). The drill sequence included baseline, pilot, second and third drills at 1200 rpm and 40 Ncm. Infrared thermographic measurements were performed using a Fluke TiS55+ camera, with a resolution of 220 × 165 pixels and a temperature range of -20 °C to 450 °C. Statistical analysis consisted of ANOVA with Bonferroni post hoc test and linear regression model, with a view to evaluate the influence of the variables on final temperature changes.

RESULTS

Irrigation caused a much lower temperature across all implant systems (P < .001). When not irrigated, Arcys showed the highest temperatures, while in both NeoBiotech and Osstem the heat dissipated better. The Bonferroni post hoc test revealed no significant temperature difference existed among implant systems without irrigation. With irrigation, however, Arcys had a higher temperature than NeoBiotech and Osstem (P < .001). The type of motor had no statistically significant influence on the temperature of the final drilling (P > .05). Based on the regression analysis, the baseline, pilot, and second drill temperatures were the strongest predictors of the final drill temperature, with irrigation influencing the effects of the drill temperature.

CONCLUSION

Irrigation decreased the thermal stress during osteotomy, while NeoBiotech and Osstem showed better heat dispersing abilities. The motor type does not have a significant influence on the temperature differences. These findings establish the basic need for effective irrigation protocols to avoid thermal osteodisruption and promote osseointegration in implantology.

Dual photoacoustic/ultrasound technologies for preclinical research: current status and future trends

Photoacoustic (PA) imaging, by integrating optical and ultrasound (US) modalities, combines high spatial resolution with deep tissue penetration, making it a transformative tool in biomedical research. This review presents a comprehensive analysis of the current status of dual PA/US imaging technologies, emphasising their applications in preclinical research. It details advancements in light excitation strategies, including tomographic and microscopic modalities, innovations in pulsed laser and alternative light sources, and US instrumentation. The review further explores preclinical methodologies, encompassing dedicated instrumentation, signal processing, and data analysis techniques essential for PA/US systems. Key applications discussed include the visualisation of blood vessels, micro-circulation, and tissue perfusion; diagnosis and monitoring of inflammation; evaluation of infections, atherosclerosis, burn injuries, healing, and scar formation; assessment of liver and renal diseases; monitoring of epilepsy and neurodegenerative conditions; studies on brain disorders and preeclampsia; cell therapy monitoring; and tumour detection, staging, and recurrence monitoring. Challenges related to imaging depth, resolution, cost, and the translation of contrast agents to clinical practice are analysed, alongside advancements in high-speed acquisition, artificial intelligence-driven reconstruction, and innovative light-delivery methods. While clinical translation remains complex, this review underscores the crucial role of preclinical studies in unravelling fundamental biomedical questions and assessing novel imaging strategies. Ultimately, this review delves into the future trends of dual PA/US imaging, highlighting its potential to bridge preclinical discoveries with clinical applications and drive advances in diagnostics, therapeutic monitoring, and personalised medicine.

Conductive Hybrid Hydrogel of Carbon Nanotubes-Protein-Cellulose: In Vivo Treatment of Diabetic Wound via Photothermal Therapy and Tracking Real-Time Wound Assessment via Photoacoustic Imaging

Diabetic wounds pose significant challenges in healthcare due to their slow healing rates and susceptibility to infections, leading to severe complications. In this study, we developed a carbon nanotube-based conductive protein-cellulose hydrogel designed to enhance wound healing through photothermal therapy. The hydrogel's unique properties, including high electrical conductivity and biocompatibility, were assessed in vitro for cell viability, hemolysis, and histological evaluations. In vivo studies on diabetic rats revealed that the hydrogel significantly improved wound healing, with faster wound closure rates. These results were supported by noticeable reductions in inflammatory markers and enhanced blood vessel formation, as observed through immunohistochemical analysis. Additionally, photoacoustic imaging offered real-time data on blood flow and tissue oxygen levels, showing positive trends in the healing process. Overall, these findings point to the potential of this conductive hydrogel, especially when paired with photothermal therapy, to serve as an effective treatment for diabetic wounds, offering promising possibilities in wound care strategies.

Application of infrared thermography for predicting pressure injury healing: A prospective study

BACKGROUND

An accurate assessment of pressure injury healing is crucial for the timely implementation of nursing intervention. This study aimed to investigate the accuracy of infrared thermography-based wound temperature measurement in predicting wound outcomes.

METHODS

This prospective, 16 days observational study included 156 adults with pressure injury. The temperature of wound bed, periwound skin and normal skin was recorded by using infrared thermography every three days. After that, three relative temperatures of PI were analyzed. The aim was to assess the significance of wound temperature in predicting healing outcomes for pressure injuries.

RESULTS

Relative temperature between periwound skin and normal skin was positively correlated with pressure injury healing (r > 0.64). Particularly the first day of follow up, it was found to be closely related to pressure injury healing (r = 0.687). On the last day and median time (the eighth to ninth day) of follow up, the optimal cutoff values of the indicator were negative values (periwound skin temperature was lower than normal skin). COX proportional hazard regression model analysis showed that relative temperature between periwound skin and normal skin on the first day of follow-up was the most significant predictor of pressure injury healing, and the healing risk increased largest- 8.79 times (95%CI: 4.53, 17.05), when its temperature greater than 0.000 °C.

CONCLUSION

Relative temperature between periwound skin and normal skin monitoring by infrared thermography better than visual assessment which can objectively serve as an indicator for predicting the healing status of pressure injury.

Evaluations of a Cutaneous Wound Healing Model Using Oxygen Enhanced - Dynamic Contrast Enhanced Photoacoustic Imaging (OE-DCE PAI)

PURPOSE

Preclinical models of cutaneous wound healing can be useful for improving clinical wound care. Oxygen Enhanced Photoacoustic imaging (OE PAI) can measure oxygenation, and Dynamic Contrast Enhanced (DCE) PAI can measure vascular perfusion. We investigated how a combined OE-DCE PAI protocol can measure vascular oxygenation and perfusion to a cutaneous healing model.

PROCEDURES

We developed a cutaneous "punch" wound model and photographed the wounds to track healing for 9 days. We performed OE-DCE PAI on Day 0, 3, 6, and 9. OE PAI was performed with 21% O2 and 100% O2 breathing gases to measure oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), total hemoglobin (HbT), and oxygen saturation (%sO2), along with changes in these parameters caused by a change in breathing gas (ΔHb, ΔHbO2, ΔHbT, ΔsO2). To perform DCE PAI, indocyanine green (ICG) was administered intravenously while monitoring the PAI signal for 10 min as the agent washed through the wound area, which was used to evaluate the wash-out rate.

RESULTS

The average wound size was significantly smaller only by Day 6. For comparison, OE PAI measured a significant increase in HbO2, Hb, HbT, and %sO2 immediately after creating the wound, which significantly decreased by Day 3 and continued to decrease towards values for normal tissue by Day 9. The vascular wash-out rate significantly increased by Day 3, and continued to increase during the healing process. Notably, the wash-out rate can be assessed at a single PAI absorbance wavelength and by simply comparing signal amplitudes without advanced analysis, which may facilitate clinical translation.

CONCLUSIONS

OE-DCE PAI can monitor significant changes in vascular perfusion and oxygenation prior to significant changes in cutaneous wound size. These results establish OE-DCE PAI as a tool for future pre-clinical wound healing studies and eventual clinical translation.

One Molecule, Many Faces: Repositioning Cardiovascular Agents for Advanced Wound Healing

Chronic wound treatments pose a challenge for healthcare worldwide, particularly for the people in developed countries. Chronic wounds significantly impair quality of life, especially among the elderly. Current research is devoted to novel approaches to wound care by repositioning cardiovascular agents for topical wound treatment. The emerging field of medicinal products' repurposing, which involves redirecting existing pharmaceuticals to new therapeutic uses, is a promising strategy. Recent studies suggest that medicinal products such as sartans, beta-blockers, and statins have unexplored potential, exhibiting multifaceted pharmacological properties that extend beyond their primary indications. The purpose of this review is to analyze the current state of knowledge on the repositioning of cardiovascular agents' use and their molecular mechanisms in the context of wound healing.

Mini review of photoacoustic clinical imaging: a noninvasive tool for disease diagnosis and treatment evaluation

Significance

Photoacoustic (PA) imaging is an imaging modality that integrates anatomical, functional, metabolic, and histologic insights. It has been a hot topic of medical research and draws extensive attention.

Aim

This review aims to explore the applications of PA clinical imaging in human diseases, highlighting recent advancements.

Approach

A systemic survey of the literature concerning the clinical utility of PA imaging was conducted, with a particular focus on its application in tumors, autoimmune diseases, inflammatory conditions, and endocrine disorders.

Results

PA imaging is emerging as a valuable tool for human disease investigation. Information provided by PA imaging can be used for diagnosis, grading, and prognosis in multiple types of tumors including breast tumors, ovarian neoplasms, thyroid nodules, and cutaneous malignancies. PA imaging facilitates the monitoring of disease activity in autoimmune and inflammatory diseases such as rheumatoid arthritis, systemic sclerosis, arteritis, and inflammatory bowel disease by capturing dynamic functional alterations. Furthermore, its unique capability of visualizing vascular structure and oxygenation levels aids in assessing diabetes mellitus comorbidities and thyroid function.

Conclusions

Despite extant challenges, PA imaging offers a promising noninvasive tool for precision disease diagnosis, long-term evaluation, and prognosis anticipation, making it a potentially significant imaging modality for clinical practice.

Bacteriophage entrapped chitosan microgel for the treatment of biofilm-mediated polybacterial infection in burn wounds

Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) bacteria are most commonly present in burn wound infections. Multidrug resistance (MDR) and biofilm formation make it difficult to treat these infections. Bacteriophages (BPs) are proven as an effective therapy against MDR as well as biofilm-associated wound infections. In the present work, a naturally inspired bacteriophage cocktail loaded chitosan microparticles-laden topical gel has been developed for the effective treatment of these infections. Bacteriophages against MDR S. aureus (BPSAФ1) and P. aeruginosa (BPPAФ1) were isolated and loaded separately and in combination into the chitosan microparticles (BPSAФ1-CHMPs, BPPAФ1-CHMPs, and MBP-CHMPs), which were later incorporated into the SEPINEO™ P 600 gel (BPSAФ1-CHMPs-gel, BPPAФ1-CHMPs-gel, and MBP-CHMPs-gel). BPs were characterized for their morphology, lytic activity, burst size, and hemocompatibility, and BPs belongs to Caudoviricetes class. Furthermore, BPSAФ1-CHMPs, BPPAФ1-CHMPs, and MBP-CHMPs had an average particle size of 1.19 ± 0.11, 1.42 ± 0.21, and 2.84 ± 0.28 μm, respectively, and expressed promising in vitro antibiofilm eradication potency. The ultrasound and photoacoustic imaging in infected burn wounds demonstrated improved wound healing reduced inflammation and increased oxygen saturation following treatment with BPs formulations. The obtained results suggested that the incorporation of the BPs in the MP-gel protected the BPs, sustained the BPs release, and improved the antibacterial activity.

Niche preclinical and clinical applications of photoacoustic imaging with endogenous contrast

In the past decade, photoacoustic (PA) imaging has attracted a great deal of popularity as an emergent diagnostic technology owing to its successful demonstration in both preclinical and clinical arenas by various academic and industrial research groups. Such steady growth of PA imaging can mainly be attributed to its salient features, including being non-ionizing, cost-effective, easily deployable, and having sufficient axial, lateral, and temporal resolutions for resolving various tissue characteristics and assessing the therapeutic efficacy. In addition, PA imaging can easily be integrated with the ultrasound imaging systems, the combination of which confers the ability to co-register and cross-reference various features in the structural, functional, and molecular imaging regimes. PA imaging relies on either an endogenous source of contrast (e.g., hemoglobin) or those of an exogenous nature such as nano-sized tunable optical absorbers or dyes that may boost imaging contrast beyond that provided by the endogenous sources. In this review, we discuss the applications of PA imaging with endogenous contrast as they pertain to clinically relevant niches, including tissue characterization, cancer diagnostics/therapies (termed as theranostics), cardiovascular applications, and surgical applications. We believe that PA imaging's role as a facile indicator of several disease-relevant states will continue to expand and evolve as it is adopted by an increasing number of research laboratories and clinics worldwide.

Review of imaging test phantoms

Significance

Photoacoustic tomography has emerged as a prominent medical imaging technique that leverages its hybrid nature to provide deep penetration, high resolution, and exceptional optical contrast with notable applications in early cancer detection, functional brain imaging, drug delivery monitoring, and guiding interventional procedures. Test phantoms are pivotal in accelerating technology development and commercialization, specifically in photoacoustic (PA) imaging, and can be optimized to achieve significant advancements in PA imaging capabilities.

Aim

The analysis of material properties, structural characteristics, and manufacturing methodologies of test phantoms from existing imaging technologies provides valuable insights into their applicability to PA imaging. This investigation enables a deeper understanding of how phantoms can be effectively employed in the context of PA imaging.

Approach

Three primary categories of test phantoms (simple, intermediate, and advanced) have been developed to differentiate complexity and manufacturing requirements. In addition, four sub-categories (tube/channel, block, test target, and naturally occurring phantoms) have been identified to encompass the structural variations within these categories, resulting in a comprehensive classification system for test phantoms.

Results

Based on a thorough examination of literature and studies on phantoms in various imaging modalities, proposals have been put forth for the development of multiple PA-capable phantoms, encompassing considerations related to the material composition, structural design, and specific applications within each sub-category.

Conclusions

The advancement of novel and sophisticated test phantoms within each sub-category is poised to foster substantial progress in both the commercialization and development of PA imaging. Moreover, the continued refinement of test phantoms will enable the exploration of new applications and use cases for PA imaging.

Viewing life without labels under optical microscopes

Optical microscopes today have pushed the limits of speed, quality, and observable space in biological specimens revolutionizing how we view life today. Further, specific labeling of samples for imaging has provided insight into how life functions. This enabled label-based microscopy to percolate and integrate into mainstream life science research. However, the use of labelfree microscopy has been mostly limited, resulting in testing for bio-application but not bio-integration. To enable bio-integration, such microscopes need to be evaluated for their timeliness to answer biological questions uniquely and establish a long-term growth prospect. The article presents key label-free optical microscopes and discusses their integrative potential in life science research for the unperturbed analysis of biological samples.

Burn depth assessment by dual-wavelength light emitting diodes-excited photoacoustic imaging in rats

Accurate burn depth assessment is crucial to determine treatment plans for burn patients. We have previously proposed a method for performing burn depth assessments based on photoacoustic (PA) imaging, and we have demonstrated the validity of this method, which allows the successful detection of PA signals originating from the blood under the bloodless burned tissue, using rat burn models. Based on these findings, we started a clinical study in which we faced two technical issues: (1) When the burn depth was shallow, PA signals due to skin contamination and/or melanin in the epidermis (surface signals) could not be distinguished from PA signals originating from the blood in the dermis; (2) the size of the system was too large. To solve these issues, we propose a burn depth diagnosis based on dual-wavelength light emitting diodes (LEDs)-excited PA imaging. The use of LEDs rendered the system compact compared to the previous one that used a conventional solid-state laser. We replicated human burned skin by applying a titrated synthetic melanin solution onto the wound surface in albino rat burn models and measured their burn depths by PA excitation at 690 and 850 nm, where melanin and haemoglobin show greatly different absorption coefficients. As a result, the surface signals were eliminated by subtracting the PA signals at 690 nm from those at 850 nm. The resultant estimated burn depths were strongly correlated with the histological assessment results. The validity of the proposed method was also examined using a burn model of rats with real melanin.

Photoacoustic imaging to monitor outcomes during hyperbaric oxygen therapy: validation in a small cohort and case study in a bilateral chronic ischemic wound

Hyperbaric oxygen therapy (HBO2) is a common therapeutic modality that drives oxygen into hypoxic tissue to promote healing. Here, ten patients undergoing HBO2 underwent PA oximetry of the left radial artery and forearm pre- and post-HBO2; this cohort validated the use of PA imaging in HBO2. There was a significant increase in radial artery oxygenation after HBO2 (p = 0.002) in the validation cohort. We also include a case study: a non-diabetic male in his 50s (HB 010) presenting with bilateral ischemic and gangrenous wounds. HB 010 showed higher perfusion and oxygen saturation on the right foot than the left after HBO2 which correlated with independent surgical observations. Imaging assisted with limb salvage treatment. Hence, this work shows that PA imaging can measure changes in arterial oxygen saturation due to HBO2; it can also produce 3D maps of tissue oxygenation and evaluate response to therapy during HBO2.

Monitoring peripheral hemodynamic response to changes in blood pressure via photoacoustic imaging

Chronic wounds and amputations are common in chronic kidney disease patients needing hemodialysis (HD). HD is often complicated by drops in blood pressure (BP) called intra-dialytic hypotension. Whether intra-dialytic hypotension is associated with detectable changes in foot perfusion, a risk factor for wound formation and impaired healing remains unknown. Photoacoustic (PA) imaging is ideally suited to study perfusion changes. We scanned the feet of 20 HD and 11 healthy subjects. HD patients were scanned before and after a dialysis session whereas healthy subjects were scanned twice at rest and once after a 10 min exercise period while BP was elevated. Healthy (r = 0.70, p < 0.0001) and HD subjects (r = 0.43, p < 0.01) showed a significant correlation between PA intensity and systolic BP. Furthermore, HD cohort showed a significantly reduced PA response to changes in BP compared to the healthy controls (p < 0.0001), showing that PA can monitor hemodynamic changes due to changes in BP.

Impact of skin tone on photoacoustic oximetry and tools to minimize bias

The major optical absorbers in tissue are melanin and oxy/deoxy-hemoglobin, but the impact of skin tone and pigmentation on biomedical optics is still not completely understood or adequately addressed. Melanin largely governs skin tone with higher melanin concentration in subjects with darker skin tones. Recently, there has been extensive debate on the bias of pulse oximeters when used with darker subjects. Photoacoustic (PA) imaging can measure oxygen saturation similarly as pulse oximeters and could have value in studying this bias. More importantly, it can deconvolute the signal from the skin and underlying tissue. Here, we studied the impact of skin tone on PA signal generation, depth penetration, and oximetry. Our results show that subjects with darker skin tones exhibit significantly higher PA signal at the skin surface, reduced penetration depth, and lower oxygen saturation compared to subjects with lighter skin tones. We then suggest a simple way to compensate for these signal differences.