Photothermal Damage Research Articles

Study on the mechanism of laser-induced breakdown and damage performance of internal defects in transparent materials through local optical field modulation

This paper establishes a photothermal damage model for bubble impurities affecting laser optical field modulation based on Mie scattering theory and incorporates the effects of optical field modulation. This model elucidates the evolution mechanism of synergistic damage in fused silica, with simulation results validated through experimental verification. A novel characterization of optical breakdown due to bubble impurities is proposed, occurring on a millisecond timescale through the dynamic evolution of combustion waves. The model delineates the influence of bubble size and spacing on optical field distribution, temperature, stress distribution, and their evolutionary behaviors. The modulation of the optical field due to double bubble impurities creates a localized “hot spot,” resulting in a differential transverse contraction stress at the edges of the bubble impurities, thereby reducing the damage threshold of fused silica. The spacing of 1.1 λ represents the enhancement node for optical field modulation by double bubble impurities. Furthermore, localized oscillations in the optical field arise when the spacing between the double bubbles exceeds 1.1 λ, attributed to changes in the refractive index at the bubble defects and resonance oscillations generated by optical field modulation. This study not only enhances our understanding of the optical field modulation processes occurring at 1064 nm in the presence of bubble defects but also establishes a theoretical foundation for detecting internal defects at this wavelength without inducing surface damage.

Unified modeling of photothermal and photochemical damage.

Correlating damage outcomes to a retinal laser exposure is critical for diagnosis and choosing appropriate treatment modalities. Therefore, it is important to understand the causal relationships between laser parameters, such as wavelength, power density, and length of exposure, and any resulting injury. Differentiating photothermal from photochemical processes in an in vitro retinal model using cultured retinal pigment epithelial cells would be a first step in achieving this goal. The first-order rate constant of Arrhenius has been used for decades to approximate cellular thermal damage. A modification of this equation, called the damage integral (Ω), has been used extensively to predict the accumulation of laser damage from photothermal inactivation of critical cellular proteins. Damage from photochemical processes is less well studied and most models have not been verified because they require quantification of one or more uncharacterized chemical species. Additionally, few reports on photochemical damage report temperature history, measured or simulated. We used simulated threshold temperatures from a previous in vitro study to distinguish between photothermal and photochemical processes. Assuming purely photochemical processes also inactivate critical cellular proteins, we report the use of a photothermal Ω and a photochemical Ω that work in tandem to indicate overall damage accumulation. The combined damage integral (ΩCDI) applies a mathematical switch designed to describe photochemical damage relative to wavelength and rate of photon delivery. Although only tested in an in vitro model, this approach may transition to predict damage at the mammalian retina.

Injectable Fluorescent Neural Interfaces for Cell-Specific Stimulating and Imaging.

Building on current explorations in chronic optical neural interfaces, it is essential to address the risk of photothermal damage in traditional optogenetics. By focusing on calcium fluorescence for imaging rather than stimulation, injectable fluorescent neural interfaces significantly minimize photothermal damage and improve the accuracy of neuronal imaging. Key advancements including the use of injectable microelectronics for targeted electrical stimulation and their integration with cell-specific genetically encoded calcium indicators have been discussed. These injectable electronics that allow for post-treatment retrieval offer a minimally invasive solution, enhancing both usability and reliability. Furthermore, the integration of genetically encoded fluorescent calcium indicators with injectable bioelectronics enables precise neuronal recording and imaging of individual neurons. This shift not only minimizes risks such as photothermal conversion but also boosts safety, specificity, and effectiveness of neural imaging. Embracing these advancements represents a significant leap forward in biomedical engineering and neuroscience, paving the way for advanced brain-machine interfaces.

Remote Manipulation of TRPV1 Signaling by Near-Infrared Light-Triggered Nitric Oxide Nanogenerators for Specific Cancer Therapy.

Specific activation of transient receptor potential vanilloid member 1 (TRPV1) channels provides a new avenue for cancer treatment by inducing excessive Ca2+ influx. However, controllable manipulation of TRPV1 signaling for clinical application has remained elusive due to the challenge in finding a mild and effective method of exerting external stimulus without adverse side effects in living systems. Herein, a TRPV1-targeting near-infrared (NIR) triggered nitric oxide (NO)-releasing nanoplatform (HCuS@PDA-TRPV1/BNN6) based on polydopamine (PDA) coated hollow copper sulfide nanoparticles (HCuS NPs) is developed for specific cancer therapy. Upon NIR irradiation, the NO donor BNN6 encapsulated in NIR-responsive nanovehicles can locally generate NO to activate TRPV1 channels and induce Ca2+ influx. This NIR controlled mode enables the nanoplatform to exert its therapeutic effects below the apoptotic threshold temperature (43°C), minimizing the photothermal damage to normal tissue. Integrating this special NO-mediated therapy with HCuS NPs mediated chemodynamic therapy, the designed nanoplatform exhibits a boosted anticancer activity with negligible systematic toxicity. Together, this study provides a promising strategy for site-specific cancer therapy by spatiotemporally controlled activation of surface ion channels, thus offering a solution to an unmet clinical need in cancer treatment.

Investigation of the photothermal weak absorption and laser damage characteristics of a Nd,Y:SrF2 crystal

The exponential-Chapman quantitative relationship is established between photothermal weak absorption and laser damage characteristics induced by surface defects in Nd,Y:SrF2 crystals.

Review of NIR-responsive ''Smart'' carriers for photothermal chemotherapy.

This review focuses on the versatile applications of near-infrared (NIR)-responsive smart carriers in biomedical applications, particularly drug delivery and photothermal chemotherapy. These carriers demonstrate multi-responsive theranostics capabilities, including pH-dependent drug release, targeted delivery of chemotherapeutics, heat-mediated drug release, and photothermal tumor damage. Biological samples are transparent to NIR light with a suitable wavelength, and therefore, NIR light is advantageous for deep-tissue penetration. It also generates sufficient heat in tissue samples, which is beneficial for on-demand NIR-responsive drug delivery in vivo systems. The development of biocompatible materials with sufficient NIR light absorption properties and drug-carrying functionality has shown tremendous growth in the last five years. Thus, this review offers insights into the current research development of NIR-responsive materials with therapeutic potential and prospects aimed at overcoming challenges to improve the therapeutic efficacy and safety in the dynamic field of NIR-responsive drug delivery.

Intelligent gold nanoparticles for malignant tumor treatment via spontaneous copper manipulation and on-demand photothermal therapy based on copper induced click chemistry.

The excessive copper in tumor cells is crucial for the growth and metastasis of malignant tumor. Herein, we fabricated a nanohybrid to capture, convert and utilize the overexpressed copper in tumor cells, which was expected to achieve copper dependent photothermal damage of primary tumor and copper-deficiency induced metastasis inhibition, generating accurate and effective tumor treatment. The nanohybrid consistsed of 3-azidopropylamine, 4-ethynylaniline and N-aminoethyl-N'-benzoylthiourea (BTU) co-modified gold nanoparticles (AuNPs). During therapy, the BTU segment would specifically chelate with copper in tumor cells after endocytosis to reduce the intracellular copper content, causing copper-deficiency to inhibit the vascularization and tumor migration. Meanwhile, the copper was also rapidly converted to be cuprous by BTU, which further catalyzed the click reaction between azido and alkynyl on the surface of AuNPs, resulting in on-demand aggregation of these AuNPs. This process not only in situ generated the photothermal agent in tumor cells to achieve accurate therapy avoiding unexpected damage, but also enhanced its retention time for sustained photothermal therapy. Both in vitro and in vivo results exhibited the strong tumor inhibition and high survival rate of tumor-bearing mice after application of our nanohybrid, indicating that this synergistic therapy could offer a promising approach for malignant tumor treatment. STATEMENT OF SIGNIFICANCE: The distinctive excessive copper in tumor cells is crucial for the growth and metastasis of tumor. Therefore, we fabricated intelligent gold nanoparticles to simultaneously response and reverse this tumorigenic physiological microenvironment for the synergistic therapy of malignant tumor. In this study, for the first time we converted and utilized the overexpressed Cu2+ in tumor cells to trigger intracellular click chemistry for tumor-specific photothermal therapy, resulting in accurate damage of primary tumor. Moreover, we effectively manipulated the content of Cu2+ in tumor cells to suppress the migration and vascularization of malignant tumor, resulting in effective metastasis inhibition.

In Vivo Laser-Induced Vasoactive Microenvironmental Setting via a Stimuli-Responsive Microstructured Depot.

A stimuli-responsive polymeric three-dimensional microstructured film (PTMF) is a 3D structure with an array of sealed chambers on its external surface. In this work, we demonstrate the use of PTMF as a laser-triggered stimulus-response system for local in vivo targeted blood vessels stimulation by vasoactive substances. The native vascular networks of the mouse mesentery were used as model tissues. Epinephrine and KCl were used as vasoactive agents that were sealed into individual chambers upon precipitation in the amount of pictograms. We demonstrated the method for non-damaged one-by-one chamber activation using a focused 532 nm laser light passed through biological tissues. To avoid laser-induced photothermal damage to biological tissues, the PTMF was functionalized with Nile Red dye, which effectively absorbs laser light. Chemically stimulated blood vessel fluctuations were analyzed using digital image processing methods. Hemodynamics changes were measured and visualized using the particle image velocimetry approach.

The Effects of Multiple Power Densities of Carbon Dioxide Laser on Photothermal Damage in Rat Skin Tissue

A CO2 laser produces infrared photons that are largely absorbed by the skin and cause morphological alterations. Twenty-four (Wistar) rats weighing 290-380 g and ranging in age from 8 months to a year were chosen at random and divided into sixteen rats for histological examination and eight rats for tensile testing to determine the extent of injury caused by photothermal damage induced by multiple doses of a CO2 laser. Anesthesia was achieved with intramuscular doses of 10 mg/kg ketamine and 60 mg/kg Xylazine. Two equal 0.5 cm surgical incisions of rat dorsal skin were performed on the left and right sides. One was utilized as a control while the other was subjected to a 10600 nm CO2 laser at various power levels (12.5, 14.1, 15.6, and 17.2) W/cm2. According to the histological analysis, the non-irradiated skin appeared to be flawless, and normal skin layers were observed. The amount of radiation in the irradiated skin samples was closely related to tissue damage. Higher dosages of irradiation resulted in the most severe cellular mutilation. Tissue injury manifested as epidermal obliteration, coagulation, homogeneous hyalinization, and hair loss. The effects of CO2 laser interaction with the skin were explored in-depth in this study. Exposure to the CO2 laser resulted in severe burns and coagulation.

Precise Starving Therapy via Physiologically Dependent Photothermal Conversion Promoted Mitochondrial Calcification Based on Multi‐Functional Gold Nanoparticles for Effective Tumor Treatment

AbstractStarving therapy based on tumor calcification has been considered as a promising strategy with high biosafety for tumor treatment. However, the limited calcium (Ca2+) concentration in/around tumor tissue as well as the slow and uncontrollable process of the physiological calcification are all challenges for its application. Herein, a sialic acid (SA, Ca2+ chelator), folic acid (FA, tumor targeting agent) and triphenylphosphine (TPP, mitochondrial targeting agent) co‐modified gold nanoparticles (SFT‐Au) are fabricated to take advantage of the abundant Ca2+ in mitochondria as well as the Ca2+ collection and Ca2+ dependent photothermal property of SFT‐Au to achieve a precise and promoted calcification of tumor mitochondria for effective starving therapy. During therapy, the SFT‐Au will first accumulate in tumor mitochondria through stepwise targeting processes medicated by FA and TPP. After that, the SA further binds with the over‐expressed Ca2+ in tumor mitochondria to induce the aggregation of SFT‐Au, which not only gathers Ca2+ to initiate the calcification of mitochondria, but in situ generates photothermal agent to perform photothermal conversion under 808 nm irradiation to promote the calcification, resulting in effective prohibition of the energy metabolism in tumor cells for starving therapy and continuously photothermal damage of tumor cells to enhance the therapeutic efficiency.

CuFeS2 Nanoparticles Functionalized with a Thermoresponsive Polymer for Photothermia and Externally Controlled Drug Delivery

CuFeS2 chalcopyrite nanoparticles (NPs) can generate heat under exposure to near-infrared laser irradiation. Here, we develop a protocol to decorate the surface of CuFeS2 NPs (13 nm) with a thermoresponsive (TR) polymer based on poly(ethylene glycol methacrylate) to combine heat-mediated drug delivery and photothermal heat damage. The resulting TR-CuFeS2 NPs feature a small hydrodynamic size (∼75 nm), along with high colloidal stability and a TR transition temperature of 41 °C in physiological conditions. Remarkably, TR-CuFeS2 NPs, when exposed to a laser beam (in the range of 0.5 and 1.5 W/cm2) at NP concentrations as low as 40-50 μg Cu/mL, exhibit a high heating performance with a rise in the solution temperature to hyperthermia therapeutic values (42-45 °C). Furthermore, TR-CuFeS2 NPs worked as nanocarriers, being able to load an appreciable amount of doxorubicin (90 μg DOXO/mg Cu), a chemotherapeutic agent whose release could then be triggered by exposing the NPs to a laser beam (through which a hyperthermia temperature above 42 °C could be reached). In an in vitro study performed on U87 human glioblastoma cells, bare TR-CuFeS2 NPs were proven to be nontoxic at a Cu concentration up to 40 μg/mL, while at the same low dose, the drug-loaded TR-CuFeS2-DOXO NPs displayed synergistic cytotoxic effects due to the combination of direct heat damage and DOXO chemotherapy, under photo-irradiation by a 808 nm laser (1.2 W/cm2). Finally, under a 808 nm laser, the TR-CuFeS2 NPs generated a tunable amount of reactive oxygen species depending on the applied power density and NP concentration.

Laser–tissue interaction simulation considering skin-specific data to predict photothermal damage lesions during laser irradiation

Abstract This study aimed to develop a simulation model that accounts for skin-specific properties in order to predict photothermal damage during skin laser treatment. To construct a computational model, surface geometry information was obtained from an optical coherence tomography image, and the absorption coefficient of the skin was determined through spectrophotometry. The distribution of the internal light dose inside the skin medium was calculated using the light propagation model based on the Monte Carlo method. The photothermal response due to the absorption of laser light was modeled by a finite difference time domain model to solve the bio-heat transfer equation. The predicted depth and area of the damaged lesions from the simulation model were compared to those measured in ex vivo porcine skin. The present simulation model gave acceptable predictions with differences of approximately ∼10% in both depth and area.

Porphyrin-based porous organic polymer coated ZIF-8 nanoparticles as tumor targeted photosensitizer for combination cancer photodynamic/photothermal therapy

The issue of low tumor-targeting and easy aggregation of small-molecule photosensitizers (PSs), as well as the heterogeneity and complexity of tumor tissue, greatly limit the therapeutic efficiency of phototherapy. Herein, a porphyrin-based organic polymer (POP) coated zeolitic imidazolate framework-8 (ZIF-8) hybrid nanoparticles (POP@ZIF-8) was developed, for delivering photosensitizer (porphyrin-based POP) specifically into tumor sites. The low-cost, biocompatible, tumor-specific POP@ZIF-8 with core-shell structure was prepared via a simple but efficient covalent surface-coating strategy, in which the pH-responsive ZIF-8 functioned as templates, finely controlling the nanometer size of the hybrid and ensuring targeted delivery of PSs to tumor tissue. Moreover, a direct covalently coated polymer-based PSs on ZIF-8 can better preserve optical properties compared to conventional physical adsorption methods. Under laser irradiation, the resulting hybridization not only efficiently converts light into local heat, causing severe photothermal damage to tumor tissue, but also synergistically promotes the production of strongly toxic 1O2, which exerts a photodynamic treatment on tumor sites. Therefore, this special POP@ZIF-8 hybrid presented a cooperatively enhanced synergistic photodynamic/photothermal anticancer efficacy, as demonstrated both the in vitro and in vivo assay, systematically. This study presents a practicable and reliable strategy to develop stable and high-efficiency cancer phototherapy agents which could simultaneously manipulate the structural characteristics and performance of targeted materials for promising noninvasive multi-mode anti-cancer.

Ultrashort pulsed Femtosecond UV laser for selective cleaning of significant Cretaceous flints

This work reports on studies aimed to evaluate the utilization of ultrashort 238 fs (fs) pulsed UV laser emission at 343 nm for eliminating colored crusts and surface deposits on significant Cretaceous flint surfaces, in an attempt to safeguard its aesthetic appearance and archaeological value. The results indicate that fs UV lasers may be an ideal, non-contact tool for selective surface cleaning of sensitive archaeological artefacts, since they enable contaminant desorption while avoiding photothermal damage.

Superstructures of water-dispersive hydrophobic nanocrystals: specific properties.

Here, we describe water-soluble superstructures of hydrophobic nanocrystals that have been developed in recent years. We will also report on some of their properties which are still in their infancy. One of these structures, called "cluster structures", consists of hydrophobic 3D superlattices of Co or Au nanocrystals, covered with organic molecules acting like parachutes. The magnetic properties of Co "cluster structures" a retained when the superstructures is dispersed in aqueous solution. With Au "cluster structures", the longer wavelength optical scattered spectra are very broad and red-shifted, while at shorter wavelengths the localized surface plasmonic resonance of the scattered nanocrystals is retained. Moreover, the maximum of the long-wavelength signal spectra is linearly dependent on the increase in assembly size. The second superstructure was based on liquid-liquid instabilities favoring the formation of Fe3O4 nanocrystal shells (colloidosomes) filled or unfilled with Au 3D superlattices and also spherical solid crystal structures are called supraballs. Colloidosomes and supraballs in contact with cancer cells increase the density of nanocrystals in lysosomes and near the lysosomal membrane. Importantly, the structure of their organization is maintained in lysosomes for up to 8 days after internalization, while the initially dispersed hydrophilic nanocrystals are randomly aggregated. These two structures act as nanoheaters. Indeed, due to the dilution of the metallic phase, the penetration depth of visible light is much greater than that of homogeneous metallic nanoparticles of similar size. This allows for a high average heat load overall. Thus, the organic matrix acts as an internal reservoir for efficient energy accumulation within a few hundred picoseconds. A similar behavior was observed with colloidosomes, supraballs and "egg" structures, making these superstructures universal nanoheaters, and the same behavior is not observed when they are not dispersed in water (dried and deposited on a substrate). Note that colloidosomes and supraballs trigger local photothermal damage inaccessible to isolated nanocrystals and not predicted by global temperature measurements.

Toward photothermal damage detection during laser osteotomy using optical coherence tomography

Feedback systems have been utilized to reduce the possible thermal side effects of lasers for surgery by means of temperature monitoring to control irrigation systems. In this study, we investigated the potential application of optical coherence tomography as a means of detecting bone dehydration status. We investigated the penetration depth of the OCT laser and its respective relation to the hydration status of bone. A deep-learning method was utilized to differentiate between different levels of water content in bone tissue (fresh/hydrated, dehydrated, and carbonized) based on the OCT images. The proposed model achieved an accuracy of 0.912 on an independent test set, demonstrating its ability to accurately predict the state of the bone considering these three conditions. We believe this method can potentially accelerate the detection of dehydration during laser surgery, improving the safety of using lasers with real-time feedback.

A Strategy of On-Demand Immune Activation for Antifungal Treatment Using Near-Infrared Responsive Conjugated Polymer Nanoparticles.

Pathogenic fungal infection is a major clinical threat because pathogenic fungi have developed resistant mechanisms to evade the innate immune response, especially interactions with macrophages. Herein, a strategy to activate immune responses of macrophages to fungi based on near-infrared (NIR) responsive conjugated polymer nanoparticles (CPNs-M) is reported for antifungal immunotherapy. Under NIR light irradiation, CPNs-M exposes β-glucan on the surface of fungal conidia by photothermal damage and drug released from CPNs-M. The exposed β-glucan elicits macrophage recognition and subsequently activates calcium-calmodulin (Ca2+-CaM) signaling followed by the LC3-associated phagocytosis (LAP) pathway to kill fungal conidia. Consequently, a remarkable elimination of intracellular fugal conidia and successful treatment of fungal pneumonia are achieved. This remote regulation strategy to restore pathogen-immune cell interaction on demand provides a new insight into combatting intractable intracellular infections.

Double pass 595-nm dye laser is not more effective than single pass: A systematic review and meta-analysis.

Dear Editor, Port wine stain (PWS) is a congenital capillary malformation, affecting 0.3%–0.5% of the population.1 It is characterized by a single pink and flat patch in infancy and may become thicken and darken during adults life, which significantly disturb the patients’ quality of life. Puled dye laser (PDL) has become the gold standard treatment of PWS.2, 3 However, there are only a minority of patients achieving total clearance of the PWS.4 To improve the clearance rate of PWS, the concept of double-pass pulsed-dye laser (DPL) and single-pass pulsed-dye laser (SPL) were introduced. Nevertheless, compared to SPL, DPL has shown variable results.5-10 The current position of DPL and SPL in the therapeutic scheme of PWS is lacking evidence-based recommendations on efficacy and side effect. This meta-analysis aims to compare the efficacy and tolerability of DPL versus SPL. The study protocol was preregistered on PROSPERO (CRD42022299613). PUBMED, EMBASE, Web of Science and Cochrane library of randomized Controlled Trials were searched without any date restrictions. In addition, we searched the reference articles of eligibility studies reported. We excluded articles involving the use of dye laser combined with other laser equipment or topical drugs. Lingling Yang and Xiaoyu Sun independently extracted data from included studies. Four outcomes were used to compare the effect and safety: better clearance rate, visual improvement scale, blanching rate, and side effect rate. The meta-analysis was performed with the Review Manager software (RevMan 5.3.5). We assessed the risk of bias of randomized controlled trials (RCTs) by The Risk of Bias Tool. Funnel plots were assessed to detect potential publication bias. We calculated I2 statistics to examine the level of Heterogeneity. And, we did an additional sensitivity analysis with respect to trials included. Six trials comprising 130 patients were included after full-text screening. Study characters can be found in Table 1. The pooled analysis revealed no significant difference between DPL and SPL in blanching rate (MD = 0.04, 95% CI: −0.07 to 0.16, P = 0.46), better clearance rate (RR = 1.60, 95%CI:0.80 to 3.22, P = 0.19) and visual improvement (MD = 0.04, 95%CI:−0.28 to 0.36, p = 0.81). Furthermore, there was no difference in the side effect between two groups (RR = 1.17, 95% CI: 0.60 to 2.28, p = 0.65) (Figure 1). We used fixed-effects model when the statistical heterogeneity was not important. The random-effects model was used if the statistical heterogeneity was moderate. All of the pooled effects and side effects remain relatively stable in sensitivity analyses. 3 sessions 1 months interval DPL: 2 hyperpigmentation SPL: 1 hyperpigmentation Randomized, single-blinded, self-control-led comparative study 3 sessions 2 months interval DPL: 3 hyperpigmentation SPL: 3 hyperpigmentation 4 sessions 3 weeks interval 7 mm,1.5 ms 12 J/cm2 2 sessions 6–10 weeks interval DPL: 4 hyperpigmentation 2 hypopigmentation 1 scar SPL: 4 hyperpigmentation 2 hypopigmentation 10 mm, 0.45–1.5 ms 6–9 J/cm2+ 10 mm, 6 ms 7.5 J/cm2 (at a 2-day interval) 10 mm, 0.45–1.5 ms 6–9 J/cm2 2 sessions 4–8 weeks interval DPL: 1 Hypopigmentation 1 hyperpigmentation SPL: 1 Hypopigmentation 1 hyperpigmentation The current evidence demonstrated that DPL had similar efficacy and side effects with SPL. There are multiple possible reasons for the similar results. First, skin lesion depth of PWS ranges from 1 to 5 mm.11 But, PDL had limited ability to affect vessels residing deeper than 2 mm in the skin12, 13 Double pass depth of vascular injury was 2.78 ± 0.9 mm for inter-pulse interval of 30 min, which was significantly greater than SPL (0.9 ± 0.2 mm),14 but this therapy was conducted on normal skin, not PWS lesions. Another trail's results indicated photothermal damage of a similar depth after SPL and DPL therapies, with mildly greater vessel wall damage on the DPL-treated sides.7 Therefore, whether the depth of vascular injury in DPL increases is unknown. Second, Previous studies had shown that angiogenesis pathways (specifically vascular endothelial growth factor and hypoxia inducible factor-1α) were activated during the wound healing process.15-17 Compared to SPL, the more serious injury of DPL may lead to more postlaser revascularizations, indicating the limited effect of PDL. This study had a few limitations. First, three randomized studies had a high risk of bias; two randomized trails had a moderate risk of bias. However, our analysis included only prospective, controlled studies to capture the evidence available. Second, the total number of studies and patients with PWS was low. Nonetheless, all the included trails were RCTs. In conclusion, at present, PWS cannot be cured completely, although PDL was considered as the gold standard treatment. This combined systematic review demonstrated that the effectiveness of DPL was comparable to SPL. The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported. Research data are not shared.

Synthesis and Characterization of Gold Nanorods and Their Application for Photothermal Cell Damage [Retraction

[This retracts the article DOI: 10.2147/IJN.S11600.].

Effects of the cone angle on the SERS detection sensitivity of tapered fiber probes.

In this paper, we investigate the effects of taper angle on the SERS detection sensitivity using tapered fiber probes with single-layer uniform gold spherical nanoparticles (GSNs). We show that the photothermal damage caused by excessive excitation laser power is the main factor that restricts the improvement of detection sensitivity of tapered fiber probes. Only when the cone angle is appropriate can a balance be achieved between increasing the excitation laser power and suppression of the transmission and scattering losses of the nanoparticles on the tapered fiber surface, thereby obtaining the best SERS detection sensitivity. Furthermore, the optimal cone angle depends on the complex refractive index of the equivalent composite dielectric (ECD) layer containing GSNs. For three SERS fiber probes with different ECD layers, the optimal cone angles measured are between 11-13°.