Thulium: YAG vs continuous-wave thulium fiber laser enucleation of the prostate: do potential advantages of thulium fiber lasers translate into relevant clinical differences?

PURPOSE: To compare endoscopic enucleation of the prostate using a thulium: yttrium-aluminum-garnet (Tm:YAG) laser and a super-pulsed thulium fiber laser set in continuous-wave (CW) mode, and to evaluate whether theoretical advantages of thulium fiber lasers, related to their shorter wavelength, translate into relevant clinical differences. METHODS: In total, 110 patients suffering from lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia were randomized to undergo either thulium:YAG laser enucleation of the prostate (ThuLEP) or CW thulium fiber laser enucleation of the prostate (CW-ThuFLEP). Intraoperative and postoperative variables and complications were compared. Micturition improvement was assessed at 3-month follow-up using the International Prostate Symptom Score (IPSS), post-void residual urine (PVR) and maximum flow rate (Qmax). Erectile function was evaluated using the International Index of Erectile Function-5 (IIEF-5). RESULTS: No significant differences between the ThuLEP and CW-ThuFLEP groups were found in terms of operative time (70.69 vs 72.41 min), enucleation time (50.23 vs 53.33 min), enucleated tissue weight (40.2 vs 41.9 g), enucleation efficiency (0.80 vs 0.79 g/min), catheterization time (2.45 vs 2.57 days), hospital stay (2.82 vs 2.95 days) and hemoglobin drop (1.05 vs 1.27 g/dl). At 3-month follow-up, no significant differences were found in IPSS (5.09 vs 5.81), Qmax (26.51 vs 27.13 ml/s), PVR (25.22 vs 23.81 ml) and IIEF-5 (14.01 vs 14.54). CONCLUSION: ThuLEP and CW-ThuFLEP were equivalent in relieving patients from LUTS and improving micturition. Theoretical advantages of the TFL, such as shallower penetration depth and improved vaporization capacity, did not translate into relevant perioperative outcomes or clinical differences.

A comparison among RIRS and MiniPerc for renal stones between 10 and 20 mm using thulium fiber laser (Fiber Dust): a randomized controlled trial.

PURPOSE: We performed a prospective randomized comparison among Retrograde IntraRenal Surgery (RIRS) and MiniPerc (MP) for stones between 10 and 20 mm to evaluate outcomes with the same laser device: Fiber Dust. METHODS: Patients with a single renal stone between 10 and 20 mm were randomized to RIRS (Group A) versus MP (Group B). Exclusion criteria were age < 18 or > 75, presence of acute infection, coagulation impairments, cardiovascular or pulmonary comorbidities. In both groups, the Fiber Dust laser was used. A CT scan after 3 months was performed. A negative CT scan or asymptomatic patients with stone fragments < 3 mm and a negative urinary culture were the criteria to assess the stone-free status. A statistical analysis was carried out to assess success, complication and retreatment rates and need for auxiliary treatments. RESULTS: Between January 2021 and January 2022, 186 patients were enrolled (90 in Group A and 96 in Group B). Mean stone size was 15.8 mm and 14.9 mm in Group A and B, respectively (p = 0.23). The overall stone-free rate (SFR) was 73.3% for Group A and 84.4% for Group B. A higher SFR was reached for upper calyceal stones in Group A (90.4%) lower calyceal stones in Group B (91.6%). Retreatment rate (p = 0.31) and auxiliary procedure rate (p = 0.18) were comparable. Complication rate was 5.5% and 5.2% for Groups A and B, respectively. CONCLUSIONS: RIRS and MP are both effective to obtain a postoperative SFR with Fiber Dust. According to the stone position one treatment is superior to the other one.

Ejaculation-sparing thulium laser enucleation of the prostate (ES-ThuLEP): outcomes on a large cohort.

PURPOSE: To assess the effects of a new ejaculation-sparing thulium laser enucleation of the prostate (ES-ThuLEP) technique on sexual functions and micturition, in patients with lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH) and to evaluate how the surgical technique of ES-ThuLEP can lead to ejaculation preservation. METHODS: A prospective study was carried out between January 2015 and January 2018 on patients with surgical indication for BPH, who wished to preserve ejaculation. The patients were treated with ES-ThuLEP and were evaluated before and 3 and 6 months after surgery. Three validated questionnaires (ICIQ-MLUTSsex, IIEF-5 and IPSS) were used to assess changes in ejaculation, erectile function and urinary symptoms. Uroflowmetry (Qmax and Qavg), post-void residual volume and voided volume were also evaluated, to assess micturition improvement. Patients with moderate to severe erectile dysfunction were excluded. Statistical analysis was performed with the Student's t test, Chi-square test and logistic regression analysis. RESULTS: Two hundred and eighty three patients were enrolled. Ejaculation was spared in 203 and 219 patients at 3 and 6 months after surgery. No significant differences were observed between erectile function before and after surgery: baseline IIEF-5 = 16.2 ± 4.47 vs 16.7 ± 2.9 (p = 0.419) and 17.7 ± 3.2 (p = 0.410) at 3 and 6 months. Significant improvement in urinary symptoms was achieved: baseline IPSS = 19.4 ± 7.24 vs 5.8 ± 4.3 (p = 0.032) and 3.9 ± 4.1 (p = 0.029) at 3 and 6 months. CONCLUSION: ES-ThuLEP effectively preserved ejaculation in over two thirds of the patients without compromising micturition improvement or erectile function. ES-ThuLEP could be a valid treatment option for BPH in young and sexually active men.

A prospective multicenter randomized comparison between Holmium Laser Enucleation of the Prostate (HoLEP) and Thulium Laser Enucleation of the Prostate (ThuLEP).

PURPOSE: To compare intra and perioperative parameters between HoLEP and ThuLEP in the treatment of benign prostatic hyperplasia and to evaluate clinical and functional outcomes of the two procedures with a 12-month follow-up. METHODS: A prospective randomized study was performed on 236 consecutive patients who underwent ThuLEP (n = 115), or HoLEP (n = 121) in three different centers. Intra and perioperative parameters were analyzed: operative time, enucleated tissue weight, irrigation volume, blood loss, catheterization time, hospital stay and complications. Patients were evaluated preoperatively and 3 and 12 months postoperatively with the international prostate symptom score (IPSS), the quality of life (QoL) score, post-void residual volume (PVR), PSA and maximum flow rate (Qmax). RESULTS: Preoperative variables in each study arm did not show any significant difference. Compared to HoLEP, ThuLEP showed similar operative time (63.69 vs 71.66 min, p = 0.245), enucleated tissue weight (48.84 vs 51.13 g, p = 0.321), catheterization time (1.9 vs 2.0 days, p = 0.450) and hospital stay (2.2 vs 2.8 days, p = 0.216), but resulted in less haemoglobin decrease (0.45 vs 2.77 g/dL, p = 0.005). HoLEP presented a significantly higher number of patients with postoperative acute urinary retention and stress incontinence. No significant differences were found in PSA, Qmax, PVR, IPSS and QoL score during follow-up. CONCLUSION: ThuLEP and HoLEP both relieved lower urinary tract symptoms equally, with high efficacy and safety. ThuLEP detemined reduced blood loss and early postoperative complications. Catheterization time, enucleated tissue, hospital stay, operative time and follow-up parameters did not show any significant difference.

Holmium laser enucleation of the prostate with Virtual Basket mode: faster and better control on bleeding.

BACKGROUND: To compare clinical intra and early postoperative outcomes between conventional Holmium laser enucleation of the prostate (HoLEP) and Holmium laser enucleation of the prostate using the Virtual Basket tool (VB-HoLEP) to treat benign prostatic hyperplasia (BPH). METHODS: This prospective randomized study enrolled consecutive patients with BPH, who were assigned to undergo either HoLEP (n = 100), or VB-HoLEP (n = 100). All patients were evaluated preoperatively and postoperatively, with particular attention to catheterization time, operative time, blood loss, irrigation volume and hospital stay. We also evaluated the patients at 3 and 6 months after surgery and assessed maximum flow rate (Qmax), postvoid residual urine volume (PVR), the International Prostate Symptom Score (IPSS) and the Quality of Life score (QOLS). RESULTS: No significant differences in preoperative parameters between patients in each study arm were found. Compared to HoLEP, VB-HoLEP resulted in less hemoglobin decrease (2.54 vs. 1.12 g/dl, P = 0.03) and reduced operative time (57.33 ± 29.71 vs. 42.99 ± 18.51 min, P = 0.04). HoLEP and VB-HoLEP detrmined similar catheterization time (2.2 vs. 1.9 days, P = 0.45), irrigation volume (33.3 vs. 31.7 l, P = 0.69), and hospital stay (2.8 vs. 2.7 days, P = 0.21). During the 6-month follow-up no significant differences in IPSS, Qmax, PVR, and QOLS were demonstrated. CONCLUSIONS: HoLEP and VB-HoLEP are both efficient and safe procedures for relieving lower urinary tract symptoms. VB-HoLEP was statistically superior to HoLEP in blood loss and operative time. However, procedures did not differ significantly in catheterization time, hospital stay, and irrigation volume. No significant differences were demonstrated in QOLS, IPSS, Qmax and PVR throughout the 6-month follow-up. TRIAL REGISTRATION: Current Controlled Trials ISRCTN72879639; date of registration: June 25th, 2015. Retrospectively registred.

Impact of Thulium Laser Enucleation of the Prostate on Erectile, Ejaculatory and Urinary Functions.

OBJECTIVE: To test the impact of Thulium laser enucleation of the prostate (ThuLEP) on erectile and ejaculatory functions, on lower urinary tract symptoms and on quality of life (QoL). METHODS: From July 2013 to May 2015, we prospectively evaluated 177 patients with LUTS related to benign prostatic hyperplasia. All patients were assessed with the International Index of Erectile Function (IIEF-5), Male Sexual Health Questionnaire-Ejaculatory Disease (MSHQ-EjD), International Prostate Symptom Score (IPSS), QoL, PSA and uroflowmetry before and at 4 and 8 months after surgery. RESULTS: Erectile function did not show variation with IIEF-5 preoperative score 22.49 ± 1.8 and postoperative score 22.14 ± 3.1 (p = 0.195) and 22.18 ± 3.2 (p = 0.26) at 4 and 8 months after treatment. The ejaculatory function on the MSHQ-EjD test indicated the reduction of ejaculation, changing from 14.90 ± 6.88 to 5.51 ± 4.17 (p < 0.0001) and 5.38 ± 3.93 (p < 0.0001) at 4 and 8 months follow-up. IPSS score decreased from preoperative 21.12 ± 5.81 to 3.14 ± 3.16 (p < 0.0001) and 3.08 ± 3.12 (p < 0.0001) 4 and 8 months after surgery. PSA decreased from 4.50 ± 3.72 to 1.39 ± 1.04 (p < 0.0001) and 1.47 ± 1.14 ng/ml (p < 0.0001) at 4 and 8 months follow-up, while QoL score improved from 5.41 ± 0.69 to 0.57 ± 0.84 (p < 0.0001) and 0.51 ± 0.80 (p < 0.0001) at 4 and 8 months follow-up. CONCLUSIONS: ThuLEP does not affect erectile function and determines the resolution of LUTS with improvement of QoL. Loss of ejaculation did not impair the sexual intercourse activities of the patients.

Indocyanine green-marked fluorescence-guided off-clamp versus intraoperative ultrasound-guided on-clamp robotic partial nephrectomy: Outcomes on surgical procedure.

Objectives: To compare surgical and functional outcomes between off-clamp robot-assisted partial nephrectomy with indocyanine-green tumour marking through preliminary superselective embolization and on-clamp robot-assisted partial nephrectomy with intraoperative ultrasound identification of the renal mass. Material and methods: One hundred and forty patients with a single renal mass underwent indocyanine-green fluorescence-guided off-clamp robot-assisted partial nephrectomy with preoperative superselective embolization (Group A, 70 patients) versus intraoperative ultrasound-guided on-clamp robot-assisted partial nephrectomy without embolization (Group B, 70 patients). We assessed operative time, intraoperative blood loss, complications, length of stay, renal function, need for ancillary procedures and blood transfusions. Results: Mean tumour size was 24 versus 25 mm in Group A versus Group B (p = 0.19). Mean operative time was 86.5 versus 121.8 min (p = 0.02), mean blood loss was 72.8 versus 214.2 mL (p = 0.02), and mean haemoglobin drop on postoperative day 1 was 1.1 versus 2.6 g/dL (p = 0.04) in Group A versus Group B. One-month creatinine, hospital stay and enucleated tumour volume were comparable. Ten postoperative complications occurred in Group A (13.3%) and 11 in Group B (15.3%). Following superselective embolization, no patients required blood transfusions versus two patients in Group B. Postoperative selective renal embolization was needed in one case per group. Conclusions: Preoperative superselective embolization of a renal mass with indocyanine-green before off-clamp robot-assisted partial nephrectomy significantly reduces operative time and intraoperative blood loss compared to on-clamp intraoperative ultrasound-guided robot-assisted partial nephrectomy. A longer follow-up is needed to establish the effect on renal function.

Open versus Robot-Assisted Radical Cystectomy for the Treatment of pT4a Bladder Cancer: Comparison of Perioperative Outcomes.

We compared the perioperative outcomes of open (ORC) vs. robot-assisted (RARC) radical cystectomy in the treatment of pT4a MIBC. In total, 212 patients underwent ORC (102 patients, Group A) vs. RARC (110 patients, Group B) for pT4a bladder cancer. Patients were prospectively followed and retrospectively reviewed. We assessed operative time, estimated blood loss (EBL), intraoperative and postoperative complications, length of stay, transfusion rate, and oncological outcomes. Preoperative features were comparable. The mean operative time was 232.8 vs. 189.2 min (p = 0.04), and mean EBL was 832.8 vs. 523.7 mL in Group A vs. B (p = 0.04). An intraoperative transfusion was performed in 32 (31.4%) vs. 11 (10.0%) cases during ORC vs. RARC (p = 0.03). The intraoperative complications rate was comparable. The mean length of stay was shorter after RARC (12.6 vs. 7.2 days, p = 0.02). Postoperative transfusions were performed in 36 (35.3%) vs. 13 (11.8%) cases (p = 0.03), and postoperative complications occurred in 37 (36.3%) vs. 29 (26.4%) patients in Groups A vs. B (p = 0.05). The positive surgical margin (PSM) rate was lower after RARC. No differences were recorded according to the oncological outcomes. ORC and RARC are feasible treatments for the management of pT4a bladder tumors. Minimally invasive surgery provides shorter operative time, bleeding, transfusion rate, postoperative complications, length of stay, and PSM rate.

Sequencing by avidity enables high accuracy with low reagent consumption.

We present avidity sequencing, a sequencing chemistry that separately optimizes the processes of stepping along a DNA template and that of identifying each nucleotide within the template. Nucleotide identification uses multivalent nucleotide ligands on dye-labeled cores to form polymerase-polymer-nucleotide complexes bound to clonal copies of DNA targets. These polymer-nucleotide substrates, termed avidites, decrease the required concentration of reporting nucleotides from micromolar to nanomolar and yield negligible dissociation rates. Avidity sequencing achieves high accuracy, with 96.2% and 85.4% of base calls having an average of one error per 1,000 and 10,000 base pairs, respectively. We show that the average error rate of avidity sequencing remained stable following a long homopolymer.

Pathological report and prognostic meaning of Bosniak IV cysts: results from a contemporary cohort.

Introduction: Surgery is the recommended treatment for Bosniak IV renal cysts. We performed a retrospective analysis of Bosniak IV lesions surgically removed to increase evidence on their prognostic meaning. Material and methods: Patients with a Bosniak IV cyst were considered. A contrast-enhanced computed tomography (CT) scan or magnetic resonance imaging (MRI) detected a solid component with contrast enhancement. In no case a percutaneous biopsy was performed. A radical (9, 21.4%) or partial (33, 78.6%) nephrectomy was performed with laparoscopic (14, 33.3%) or robot-assisted (28, 66.7%) approach. Analysis of the final pathology was performed, and recurrence rate was assessed. Results: 42 patients were included. Median lesion size was 54.7 mm (IQR 20.0-81.2). A solid tumour was detected in 40 patients (95.2%), whereas in 2 cases (4.8%) a benign cyst without neoplastic component was diagnosed. Final pathology revealed a low-grade clear cell renal cell carcinoma (ccRCC) in 16 cases (38.0%), a multilocular cystic renal neoplasm of low malignant potential in 6 cases (14.3%), a low-grade papillary RCC (pRCC) type I in 4 cases (9.5%), a clear cell papillary RCC (ccpRCC) in 10 cases (23.8%) and an oncocytoma in 2 cases (4.8%). A high-grade ccRCC was detected in 2 cases (4.8%), whereas no patients had a pRCC type II. In all cases surgical margins were negative. Median follow-up was 24 months and no recurrence occurred. Conclusions: Our results increase evidence on the favourable pathology and good prognosis of Bosniak IV renal cysts, supporting the role of surgery as a definitive treatment and suggesting the need for a low-intensity follow-up.

Treatment of ureteral stones with LithoEVO device and Vapor Tunnel tool.

BACKGROUND: Vapor Tunnel (VT) technology is the result of a pulse modulation during holmium laser emission which reduces stone retropulsion. We present the outcomes of this tool in the treatment of ureteral stones. METHODS: Two hundred ten patients with a ureteral stone were randomly assigned to holmium laser lithotripsy with (group A) or without (group B) the VT technology. The 35 W LithoEVO laser generator (Quanta System, Samarate, Varese, Italy) was used. We compared operative time, dusting time, delivered energy, retreatment rate due to stone push-up, ureteral lesions, and stone-free rate (SFR) and postoperative strictures at 1 month. We also compared outcomes according to stone position. RESULTS: VT technology was associated with significantly lower mean operative time (25.7 vs. 37.2 min), dusting time (9.7 vs. 15.3 min), delivered energy (7.7 vs. 19.9 KJ). In group B 9 patients (8.5%) were retreated due to stone push-up (P=0.01) for a proximal or middle stone, 6 (5.7%) postoperative strictures occurred (P=0.03) and a higher ureteral lesion rate was observed (7.6% vs 35.2%, P=0.04). 1-month SFR was comparable (93.4% vs. 88.6%, P=0.11). Postoperative complication rate was higher in group B (P=0.05). Without VT technology, ureteral lesions and strictures rates were significantly higher independently from stone position. CONCLUSIONS: The VT technology is associated with significantly lower operative and dusting time independently from stone position, due to a reduced retropulsion, which makes treatment quicker and easier. It also avoids stone push-up especially for proximal and middle stones and reduces ureteral lesions, postoperative complications, and ureteral strictures.

"VirtualBasket" ureteroscopic holmium laser lithotripsy: intraoperative and early postoperative outcomes.

BACKGROUND: The "VirtualBasket" technology (Cook Medical, Bloomington, IN, USA) is the result of pulse modulation during holmium laser emission: the laser emits part of the energy to create an initial bubble, and a second pulse is emitted when the vapor bubble is at its maximum expansion, so that it can pass through the previously created vapor channel. The aim of this study was to outline the outcomes of the "VirtualBasket" technology in ureteral and renal stones. METHODS: 160 Patients were randomly assigned to holmium laser lithotripsy with or without the "VirtualBasket" technology in ureteric or renal cases (40 per 4 groups). All procedures were performed by four experienced urologists. The Quanta System Cyber Ho 100W laser generator with 365 µm fibers was used for all the ureteral cases, whereas 272 µm fibers were used for all the cases in the renal pelvis. Demographic data, stone parameters, perioperative complications and success rates were compared. A statistical analysis was carried out to assess patients' data and outcomes. All the reported P values were obtained with the two-sided exact method at the conventional 5% significance level. The degree of stone retropulsion was graded on a Likert scale from zero (no retropulsion) to 3 (maximum retropulsion). RESULTS: All groups were comparable in terms of age, and preoperative stone size (ureter stone size: 1.2 vs. 1.1 cm; renal pelvis stone size: 1.55 vs. 1.62 cm). Compared to the regular mode, the "VirtualBasket" technology was associated with significantly lower fragmentation time (mean time for ureteral stones: 20.4 vs. 16.1 minutes, P<0.05; mean time for renal stones: 28.7 vs. 19.8 minutes, P<0.05) and total procedural time (mean time for ureteral stones 49 vs. 35.7 minutes; mean time for renal stones 67.1 vs. 52.4 minutes). There were no significant differences in terms of energy delivered to the stones, intraoperative complications and success rate at 1 month. The "VirtualBasket" technology was associated with significantly lower retropulsion. CONCLUSIONS: The "VirtualBasket" technology is associated with significantly lower fragmentation and procedural times. The reduced fragmentation time is a result of the significantly lower retropulsion of the stones during laser lithotripsy, which improves stone fragmentation efficiency.

Development and Validation of a Novel Skills Training Model for PCNL, an ESUT project.

BACKGROUND AND AIM: The aim of this study is to validate a totally non biologic training model that combines the use of ultrasound and X ray to train Urologists and Residents in Urology in PerCutaneous NephroLithotripsy (PCNL). METHODS: The training pathway was divided into three modules: Module 1, related to the acquisition of basic UltraSound (US) skill on the kidney; Module 2, consisting of correct Nephrostomy placement; and Module 3, in which a complete PCNL was performed on the model. Trainees practiced on the model first on Module 1, than in 2 and in 3. The pathway was repeated at least three times. Afterward, they rated the performance of the model and the improvement gained using a global rating score questionnaire. RESULTS: A total of 150 Urologists took part in this study. Questionnaire outcomes on this training model showed a mean 4.21 (range 1-5) of positive outcome overall. Individual constructive validity showed statistical significance between the first and the last time that trainees practiced on the PCNL model among the three different modules. Statistical significance was also found between residents, fellows and experts scores. Trainees increased their skills during the training modules. CONCLUSION: This PCNL training model allows for the acquisition of technical knowledge and skills as US basic skill, Nephrostomy placement and entire PCNL procedure. Its structured use could allow a better and safer training pathway to increase the skill in performing a PCNL.

Single-molecule colocalization studies shed light on the idea of fully emitting versus dark single quantum dots.

In this report the correlation between the solution photoluminescence (PL) quantum yield and the fluorescence emission of individual semiconductor quantum dots (QDs) is investigated. This is done by taking advantage of previously reported enhancement in the macroscopic quantum yield of water-soluble QDs capped with dihydrolipoic acid (DHLA) when self-assembled with polyhistidine-appended proteins, and by using fluorescence coincidence analysis (FCA) to detect the presence of "bright" and "dark" single QDs in solution. This allows for changes in the fraction of the two QD species to be tracked as the PL yield of the solution is progressively altered. The results clearly indicate that in a dispersion of luminescent nanocrystals, "bright" (intermittently emitting) single QDs coexist with "permanently dark" (non-emitting) QDs. Furthermore, the increase in the fraction of emitting QDs accompanies the increase in the PL quantum yield of the solution. These findings support the idea that a dispersion of QDs consists of two optically distinct populations of nanocrystals--one is "bright" while the other is "dark;" and that the relative fraction of these two populations defines the overall PL yield.

Current evidence of ThuLEP for BPH: A review of literature.

Endoscopic enucleation of the prostate (EEP) techniques for the treatment of benign prostatic hyperplasia (BPH) have become increasingly popular among urologists over the past 23 years. Despite the energy source employed, the aim of all these procedures is to endoscopically remove the prostatic lobes by enucleating them from the prostate surgical capsule. The reasons for which EEP has gained popularity among urologists are the reduction in complications and hospital stay compared to endoscopic gold standard Transurethral Resection of the Prostate (TURP), but especially the possibility to treat large prostates, allowing to abandon open simple prostatectomy (OP) and to avoid the burden related to open surgery. Holmium laser enucleation of the prostate (HoLEP) sets the basic principles of all EEP techniques in 1998 and has become the treatment of reference for BPH. Since then, various lasers have been developed and applied to prostatic enucleation. The thulium laser has a slightly shorter wavelength compared to the holmium laser and a continuous wave output, which increase vaporization and reduce penetration depth. These features make it ideal for prostatic enucleation. A vapoenucleating technique called Thulium Laser Vapoenucleation of the Prostate was presented in 2009, followed by a blunt enucleating technique called Thulium Laser Enucleation of the Prostate in 2010. These techniques have become alternatives to HoLEP and TURP; however, the amount of literature and randomized controlled trials available are inferior compared to HoLEP. The aim of th describe, and discuss current evidence on thulium enucleating techniques.

An electrochemical scanning tunneling microscopy study of 2-(6-mercaptoalkyl)hydroquinone molecules on Au(111).

The hydroquinone/benzoquinone redox couple involves the exchange of two electrons and two protons in its oxidation/reduction reaction in aqueous buffered solutions. In this work, we employed Electrochemical Scanning Tunneling Microscopy and Spectroscopy (EC-STM, EC-STS) to study the interfacial electron transfer properties of hydroquinone incorporated in a Self Assembled Monolayer on a Au(111) substrate. The exchange of electrons between the STM tip and the substrate is regulated by the redox levels of the sandwiched molecule and showed the presence of two regions of tunneling enhancement in the tunneling current/overvoltage relationship. The two regions can be attributed to the presence of two one-electron transfer processes whose equilibrium positions shift upon pH variations. This is the first time a redox molecule involving the exchange of both electrons and protons is studied by EC-STM and EC-STS. The hydroquinone/benzoquinone redox couple can be exploited to obtain an electrochemically or a pH gated transistor.

Maximization of loading and stability of ssDNA:iron oxide nanoparticle complexes formed through electrostatic interaction.

The use of inorganic nanoparticles (NPs) as vectors for the delivery of oligonucleotides for in vitro and in vivo applications is rapidly gaining momentum. Some of the reasons making them especially good candidates for this purpose are their ease of synthesis in a range of sizes and surface coatings, their propensity to penetrate cell membranes, their stability and biocompatibility, and their unique size-dependent physical properties that impart additional diagnostic and therapeutic tools. Notwithstanding these notable attributes, a major obstacle to their practical use is given by the typically low oligonucleotide loading levels attainable through conventional bioconjugation procedures. This shortcoming is especially worrisome as toxicity concerns have been associated with codelivery of NPs. In this paper we are analytically analyzing the formation of electrostatic complexes between negatively charged ssDNA and positively charged iron oxide nanoparticles (SPIO-NP) with the purpose of identifying the optimal conditions leading to stable formulations at high oligo loading levels. The formation and loading levels of ssDNA:SPIO-NP complexes have been investigated at different oligo:NP ratios and under different ionic strengths through dynamic light scattering, fluorescence quenching experiments, and pull-down assays. Through these studies we have identified optimal conditions for attaining maximal oligo loading levels, and we are proposing a simple model to explain an unusual behavior observed in the formation of the complexes. Finally, we introduce an alternative loading method relying on the electrostatic coloading of an oligo sequence in the presence of a negatively charged PEGylated block copolymer, yielding very stable and high loading PEGylated ssDNA:SPIO-NPs. The findings that we are reporting are of general validity, and similar conditions could be easily translated to the electrostatic formation of ssDNA:NP complexes consisting of different NP materials and sizes.