Safe Procedure for Efficient Hydrodynamic Gene Transfer to Isolated Porcine Liver in Transplantation.

Although calcineurin inhibitors are very effective as immunosuppressants in organ transplantation, complete graft acceptance remains as a challenge. Transfer of genes with immunosuppressant functions could contribute to improving the clinical evolution of transplantation. In this sense, hydrodynamic injection has proven very efficacious for liver gene transfer. In the present work, the hIL-10 gene was hydrofected 'ex vivo' to pig livers during the bench surgery stage, to circumvent the cardiovascular limitations of the procedure, in a model of porcine orthotopic transplantation with a 10-day follow-up. We used IL-10 because human and porcine proteins can be differentially quantified and for its immunomodulatory pleiotropic functions. Safety (biochemical parameters and histology), expression efficacy (RNA transcription and blood protein expression), and acute inflammatory response (cytokines panel) of the procedure were evaluated. The procedure proved safe as no change in biochemical parameters was observed in treated animals, and human IL-10 was efficaciously expressed, with stationary plasma protein levels over 20 pg/mL during the follow-up. Most studied cytokines showed increments (interferon-α, IFN-α; interleukin-1ß, IL-1ß; tumor necrosis factor α, TNFα; interleukin-6, IL-6; interleukin-8, IL-8; interleukin-4, IL-4; and transforming growth factor-ß, TGF-ß) in treated animals, without deleterious effects on tissue. Collectively, the results support the potential clinical interest in this gene therapy model that would require further longer-term dose-response studies to be confirmed.

Alternative forms of portal vein revascularization in liver transplant recipients with complex portal vein thrombosis.

BACKGROUND & AIMS: Complex portal vein thrombosis (PVT) is a challenge in liver transplantation (LT). Extra-anatomical approaches to portal revascularization, including renoportal (RPA), left gastric vein (LGA), pericholedochal vein (PCA), and cavoportal (CPA) anastomoses, have been described in case reports and series. The RP4LT Collaborative was created to record cases of alternative portal revascularization performed for complex PVT. METHODS: An international, observational web registry was launched in 2020. Cases of complex PVT undergoing first LT performed with RPA, LGA, PCA, or CPA were recorded and updated through 12/2021. RESULTS: A total of 140 cases were available for analysis: 74 RPA, 18 LGA, 20 PCA, and 28 CPA. Transplants were primarily performed with whole livers (98%) in recipients with median (IQR) age 58 (49-63) years, model for end-stage liver disease score 17 (14-24), and cold ischemia 431 (360-505) minutes. Post-operatively, 49% of recipients developed acute kidney injury, 16% diuretic-responsive ascites, 9% refractory ascites (29% with CPA, p <0.001), and 10% variceal hemorrhage (25% with CPA, p = 0.002). After a median follow-up of 22 (4-67) months, patient and graft 1-/3-/5-year survival rates were 71/67/61% and 69/63/57%, respectively. On multivariate Cox proportional hazards analysis, the only factor significantly and independently associated with all-cause graft loss was non-physiological portal vein reconstruction in which all graft portal inflow arose from recipient systemic circulation (hazard ratio 6.639, 95% CI 2.159-20.422, p = 0.001). CONCLUSIONS: Alternative forms of portal vein anastomosis achieving physiological portal inflow (i.e., at least some recipient splanchnic blood flow reaching transplant graft) offer acceptable post-transplant results in LT candidates with complex PVT. On the contrary, non-physiological portal vein anastomoses fail to resolve portal hypertension and should not be performed. IMPACT AND IMPLICATIONS: Complex portal vein thrombosis (PVT) is a challenge in liver transplantation. Results of this international, multicenter analysis may be used to guide clinical decisions in transplant candidates with complex PVT. Extra-anatomical portal vein anastomoses that allow for at least some recipient splanchnic blood flow to the transplant allograft offer acceptable results. On the other hand, anastomoses that deliver only systemic blood flow to the allograft fail to resolve portal hypertension and should not be performed.

Abdominal normothermic regional perfusion in controlled donation after circulatory determination of death liver transplantation: Outcomes and risk factors for graft loss.

Postmortem normothermic regional perfusion (NRP) is a rising preservation strategy in controlled donation after circulatory determination of death (cDCD). Herein, we present results for cDCD liver transplants performed in Spain 2012-2019, with outcomes evaluated through December 31, 2020. Results were analyzed retrospectively and according to recovery technique (abdominal NRP [A-NRP] or standard rapid recovery [SRR]). During the study period, 545 cDCD liver transplants were performed with A-NRP and 258 with SRR. Median donor age was 59 years (interquartile range 49-67 years). Adjusted risk estimates were improved with A-NRP for overall biliary complications (OR 0.300, 95% CI 0.197-0.459, p < .001), ischemic type biliary lesions (OR 0.112, 95% CI 0.042-0.299, p < .001), graft loss (HR 0.371, 95% CI 0.267-0.516, p < .001), and patient death (HR 0.540, 95% CI 0.373-0.781, p = .001). Cold ischemia time (HR 1.004, 95% CI 1.001-1.007, p = .021) and re-transplantation indication (HR 9.552, 95% CI 3.519-25.930, p < .001) were significant independent predictors for graft loss among cDCD livers with A-NRP. While use of A-NRP helps overcome traditional limitations in cDCD liver transplantation, opportunity for improvement remains for cases with prolonged cold ischemia and/or technically complex recipients, indicating a potential role for complimentary ex situ perfusion preservation techniques.

Appraising pancreatic fistula in pancreas transplantation: A comprehensive complication index based analysis of postoperative outcomes and predictors of graft survival.

BACKGROUND: A definition of pancreatic fistula specifically addressing pancreas transplantation (PT) is lacking. This study sought to characterize pancreatic fistula in this setting and to define its clinical relevance on the postoperative course and long-term graft survival (GS). METHODS: Consecutive simultaneous pancreas and kidney transplantations were analysed. The global postoperative course was assessed through the comprehensive complication index (CCI). PF was defined according to the original International Study Group for Pancreatic Surgery (ISGPS) definition. Predictors of poor postoperative course and GS were explored. RESULTS: Seventy-eight patients were analysed. Surgical morbidity was 48.7%, with severe complications occurring in 39.7%. Ninety-day mortality was 2.6%. PF occurred in 56.6% of patients, although its average clinical burden was low and did not correlate with either early or long-term outcomes. Peri-graft fluid collections, postoperative day (POD) 1 drain fluid amylase (DFA) ≥ 2200 U/L, and POD 5 DFA/serum amylase ratio ≥7.0 independently correlated with poor postoperative course. Perigraft fluid collections were associated with reduced GS. CONCLUSION: Conventionally defined pancreatic fistula is frequent following PT, although its clinical impact is negligible. To define clinically relevant PF, novel cut-offs for DFA might be pondered in a future series, while perigraft fluid collections should be strongly considered.

Good post-transplant outcomes using liver donors after circulatory death when applying strict selection criteria: A propensity-score matched-cohort study.

INTRODUCTION AND OBJECTIVES: Outcomes of liver transplantation (LT) with donors after circulatory death (DCD) have been considered suboptimal due to higher rates of ischemic cholangiopathy, especially when the super-rapid recovery (SRR) technique is used. This study aimed to compare the incidence of complications between recipients receiving DCD vs those receiving donors after brain death (DBD) in a large-volume liver transplant centre. METHODS: We performed a retrospective cohort study (LT from January 2015 to December 2018) comparing recipients who underwent a LT with DCD vs. a control group of LT with DBD, matched 1:1 without replacement by propensity score matching that included the following variables: LT indication, recipient sex and age, donor age and MELD score. RESULTS: 51 recipients with DCD-LT (29 SRR, 22 normothermic regional perfusion [NRP]) were matched with 51 DBD-LT recipients. Biliary complications were more frequent in DCD, 10% (n=5), all with SRR technique, vs 2% (n=1) in the DBD group, p=0.2. Two patients (4%) suffered primary graft non-function in the DCD group (1 SRR and 1 NRP) versus zero in the DBD group (p=0.49). Postoperative bleeding and reinterventions were also higher in the DCD group: 7 (13.7%) vs 1 (1.95%) and 8 (15.7%) vs 2 (3.9%) respectively (p=0.06 and 0.09). On the 1st postoperative day AST/ALT peak was higher in DCD (p≤0001). The incidence of rejection, vascular complications, renal injury, hospital stay, and readmissions were similar in both groups. Cumulative 1-, 2-, 3- and 4-year graft and patient survival were also similar. CONCLUSIONS: DCD donors are an adequate option to increase the donor pool in LT, achieving similar graft and patient survival rates to those achieved with DBD donors, especially when the NRP technique is used.

Metabolic syndrome before liver transplantation: does it have an impact on post liver transplantation outcome?

INTRODUCTION: Metabolic syndrome (MS) and cardiovascular risk factors are common in liver transplant (LT) candidates and recipients. Cardiovascular events and de novo tumors are increasingly common causes of mortality in liver transplant recipients. The aim of this study were (i) assess the prevalence of MS in LT recipients and its growth over the years and (ii) determine if the presence of MS pre-LT is associated with a higher risk of post-LT cardiovascular events (CVE), de novo tumors or early and late survival. PATIENTS AND METHODS: A retrospective study was performed that included LT recipients from January 2012 to December 2017. Baseline features (MS before LT and at 1year post-LT) and outcomes (CVE, de novo tumors and survival) were recorded. RESULTS: 483 recipients were included, MS was present in 20% of pre-LT with an increasing prevalence over time, from 16% in 2012 to 34% in 2017 (p=0.025). One-year post-LT, an additional 12% had developed de novo MS. At a median of 56-months follow-up, 13% developed a CVE and 9% a de novo tumor. One and 5-yr survival rates were 91% and 83% in those with pre-LT MS and 93% and 85% in those without (p=0.94).The presence of MS before LT was independently associated with a higher risk of post-LT CVE (HR: 2.66 IC (95%): 1.6-4.4 p< 0.001), but not with de novo tumors (p=0.94) nor early and late survival (p=0.58 and p=0.87). CONCLUSION: Pre-LT MS is increasing among LT candidates and is associated with a higher risk of post-LT morbidity CVE yet without affecting mortality. .

From conventional two-stage hepatectomy to ALPPS: Fifteen years of experience in a hepatobiliary surgery unit.

BACKGROUND: Hepatectomy in patients with large tumor load may result in postoperative liver failure and associated complications due to excessive liver parenchyma removal. Conventional two-stage hepatectomy (TSH) and associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) technique are possible solutions to this problem. Colorectal liver metastases (CRLM) is the most frequent indication, and there is a need to assess outcomes for both techniques to improve surgical and long-term oncological outcomes in these patients. METHODS: A single-center retrospective study was designed to compare TSH with ALPPS in patients with initially unresectable bilateral liver tumors between January 2005 and January 2020. ALPPS was performed from January 2012 onwards as the technique of choice. Long-term overall survival (OS) and disease-free survival (DFS) were evaluated as primary outcome in CRLM patients. Postoperative morbidity, mortality and liver growth in all patients were also evaluated. RESULTS: A total of 38 staged hepatectomies were performed: 17 TSH and 21 ALPPS. Complete resection rate was 76.5% (n = 13) in the TSH group and 85.7% (n = 18) in the ALPPS group (P = 0.426). Overall major morbidity (Clavien-Dindo ≥ 3a) (stage 1 + stage 2) was 41.2% (n = 7) in TSH and 33.3% (n = 7) in ALPPS patients (P = 0.389), and perioperative 90-day mortalities were 11.8% (n = 2) vs. 19.0% (n = 4) in each group, respectively (P = 0.654). Intention-to-treat OS rates at 1 and 5 years in CRLM patients for TSH (n = 15) were 80% and 33%, and for ALPPS (n = 17) 76% and 35%, respectively. DFS rates at 1 and 5 years were 36% and 27% in the TSH group vs. 33% and 27% in the ALPPS group, respectively. CONCLUSIONS: ALPPS is an effective alternative to TSH in bilateral affecting liver tumors, allowing higher resection rate, but patients must be carefully selected. In CRLM patients similar long-term OS and DFS can be achieved with both techniques.

Portal vein aneurysm, an update on the subject. A case report.

The portal venous aneurysm(PVA) is a very rare entity, which can be congenital or acquired (if portal hypertension, cirrhosis, pancreatitis, surgical history). Although the discussion is still ongoing, treatment would be indicated in symptomatic PVA, over 30mm or progressive growth. In order to provide an update on the subject due to the low incidence of this finding, we present the case of a 51-year-old woman who comes to the ER for painful obstructive jaundice; the ultrasound shows the presence of cholelitiasis and choledicolitiasis and identifies a nodular image in continuity with the right portal branch of 25x22x21 mm. This dilation is confirmed by MRI. After committee evaluation, follow-up was decided and to reserve the possibility of embolization if growth or symptomatology appeared.

Normothermic regional perfusion vs. super-rapid recovery in controlled donation after circulatory death liver transplantation.

BACKGROUND & AIMS: Although there is increasing interest in its use, definitive evidence demonstrating a benefit for postmortem normothermic regional perfusion (NRP) in controlled donation after circulatory death (cDCD) liver transplantation is lacking. The aim of this study was to compare results of cDCD liver transplants performed with postmortem NRP vs. super-rapid recovery (SRR), the current standard for cDCD. METHODS: This was an observational cohort study including all cDCD liver transplants performed in Spain between June 2012 and December 2016, with follow-up ending in December 2017. Each donor hospital determined whether organ recovery was performed using NRP or SRR. The propensity scores technique based on the inverse probability of treatment weighting (IPTW) was used to balance covariates across study groups; logistic and Cox regression models were used for binary and time-to-event outcomes. RESULTS: During the study period, there were 95 cDCD liver transplants performed with postmortem NRP and 117 with SRR. The median donor age was 56 years (interquartile range 45-65 years). After IPTW analysis, baseline covariates were balanced, with all absolute standardised differences <0.15. IPTW-adjusted risks were significantly improved among NRP livers for overall biliary complications (odds ratio 0.14; 95% CI 0.06-0.35, p <0.001), ischaemic type biliary lesions (odds ratio 0.11; 95% CI 0.02-0.57; p = 0.008), and graft loss (hazard ratio 0.39; 95% CI 0.20-0.78; p = 0.008). CONCLUSIONS: The use of postmortem NRP in cDCD liver transplantation appears to reduce postoperative biliary complications, ischaemic type biliary lesions and graft loss, and allows for the transplantation of livers even from cDCD donors of advanced age. LAY SUMMARY: This is a propensity-matched nationwide observational cohort study performed using livers recovered from donors undergoing cardiac arrest provoked by the intentional withdrawal of life support (controlled donation after circulatory death, cDCD). Approximately half of the livers were recovered after a period of postmortem in situ normothermic regional perfusion, which restored warm oxygenated blood to the abdominal organs, whereas the remainder were recovered after rapid preservation with a cold solution. The study results suggest that the use of postmortem normothermic regional perfusion helps reduce rates of post-transplant biliary complications and graft loss and allows for the successful transplantation of livers from older cDCD donors.

Efficacy of hydrodynamic interleukin 10 gene transfer in human liver segments with interest in transplantation.

Different diseases lead, during their advanced stages, to chronic or acute liver failure, whose unique treatment consists in organ transplantation. The success of intervention is limited by host immune response and graft rejection. The use of immunosuppressant drugs generally improve organ transplantation, but they cannot completely solve the problem. Also, their management is delicate, especially during the early stages of treatment. Thus, new tools to set an efficient modulation of immune response are required. The local expression of interleukin (IL) 10 protein in transplanted livers mediated by hydrodynamic gene transfer could improve the organ acceptance by the host because it presents the natural ability to modulate the immune response at different levels. In the organ transplantation scenario, IL10 has already demonstrated positive effects on graft tolerance. Hydrodynamic gene transfer has been proven to be safe and therapeutically efficient in animal models and could be easily moved to the clinic. In the present work, we evaluated efficacy of human IL10 gene transfer in human liver segments and the tissue natural barriers for gene entry into the cell, employing gold nanoparticles. In conclusion, the present work shows for the first time that hydrodynamic IL10 gene transfer to human liver segments ex vivo efficiently delivers a human gene into the cells. Indexes of tissue protein expression achieved could mediate local pharmacological effects with interest in controlling the immune response triggered after liver transplantation. On the other hand, the ultrastructural study suggests that the solubilized plasmid could access the hepatocyte in a passive manner mediated by the hydric flow and that an active mechanism of transportation could facilitate its entry into the nucleus. Liver Transplantation 23:50-62 2017 AASLD.

Management of pancreatic gastrinoma associated with Von Hippel-Lindau disease: a case report.

BACKGROUND: Pancreatic neuroendocrine tumors (PNET) are a heterogeneous group and constitute 1.3% of all pancreatic tumors. Approximately 10% of these occur in the context of hereditary syndromes, such as VHL disease. CASE REPORT: We report a case of a female patient of 37 years diagnosed VHL and intervened on several occasions by cerebral hemangioblastoma and renal carcinomas. During its follow-up she was diagnosed 2 gastrinomas functioning under 2 cm were enucleated. Later developed new PNET and underwent a total duodenopancreatectomy without pyloric preservation. DISCUSSION: The management of PNET in VHL is difficult due to the association of multiple tumors in different organs and the morbidity and mortality associated with the surgery of the pancreas. Management must be individualized for each patient, based on the ability to produce hormones and present symptoms, the size and location, and in the context of other tumors that usually present in these patients.

Surgical anterior cavoplasty for managing a case of early acute outflow obstruction after liver transplantation.

HVOO following liver transplantation is rarely treated surgically because it tends to debut subacutely. However, acute HVOO is a surgical emergency that compromises the viability of the graft. We report a case of HVOO diagnosed intra-operatively during surgical revision for a suspected arterial thrombosis in a 10-month-old male recipient of a second graft (segments II-III) for familial intrahepatic cholestasis. HVOO was related to a stenosis at the first transplant hepato-caval anastomosis, left in place to obtain longer venous cuffs for retransplantation. An anterior cavoplasty was necessary to resolve the issue. The new anastomosis was created under total vascular exclusion after gaining control of the supradiaphragmatic vena cava, because the inferior vena cava was unsuitable for further surgery. This approach (normally used as a means to avoid sternotomy in patients with hepatic or renal tumours associated with venous thrombosis) allows adequate vascular control and, in selected cases, offers a surgical alternative for treating HVOO.

Is physical exercise harmful to liver transplantation recipients? Review of literature.

Liver transplantation is a treatment that significantly improves the patients' quality of life. However, we should be more ambitious and seek an improvement in their fitness through training protocols allowing them to fully return to daily activities. English and Spanish-language articles on PubMed and the Cochrane Library were searched untill 2014. Articles were reviewed by 2 of the authors to determine if they were suitable for inclusion. It is shown a compilation of studies that included patients who have participated in aerobic, strength, or both combined training programs, without implying a risk for the graft function. There is a lack of studies with high scientific evidence that stablish a proper exercise program methodology, supervised by specialists in physical activity and sports.

Twenty-five years of ambulatory laparoscopic cholecystectomy. / Veinticinco años de colecistectomía laparoscópica en régimen ambulatorio.

It is accepted by the surgical community that laparoscopic cholecystectomy (LC) is the technique of choice in the treatment of symptomatic cholelithiasis. However, more controversial is the standardization of system implementation in Ambulatory Surgery because of its different different connotations. This article aims to update the factors that influence the performance of LC in day surgery, analyzing the 25 years since its implementation, focusing on the quality and acceptance by the patient. Individualization is essential: patient selection criteria and the implementation by experienced teams in LC, are factors that ensure high guarantee of success.

Framingham score, renal dysfunction, and cardiovascular risk in liver transplant patients.

Cardiovascular (CV) events represent major impediments to the long-term survival of liver transplantation (LT) patients. The aim of this study was to assess whether the Framingham risk score (FRS) at transplantation can predict the development of post-LT cardiovascular events (CVEs). Patients transplanted between 2006 and 2008 were included. Baseline features, CV risk factors, and CVEs occurring after LT (ischemic heart disease, stroke, heart failure, de novo arrhythmias, and peripheral arterial disease) were recorded. In total, 250 patients (69.6% men) with a median age of 56 years (range, 18-68 years) were included. At transplantation, 34.4%, 34.4%, and 33.2% of patients, respectively, had a low, moderate, and high FRS with a median FRS of 14.9 (range, 0.09-30); 14.4% of LT recipients developed at least 1 CVE at a median of 2.619 years (range, 0.006-6.945 years). In the univariate analysis, factors associated with the development of CVEs were the continuous FRS at LT (P = 0.003), age (P = 0.007), creatinine clearance [estimated glomerular filtration rate (eGFR); P = 0.020], and mycophenolate mofetil use at discharge (P = 0.011). In the multivariate analysis, only the eGFR [hazard ratio (HR), 0.98; 95% confidence interval (CI), 0.97-1.00; P = 0.009] and FRS (HR, 1.06; 95% CI, 1.02-1.10; P = 0.002) remained in the model. Moreover, an association was also found between the FRS and overall survival (P = 0.004) with 5-year survival rates of 82.5%, 77.8%, and 61.4% for the low-, moderate-, and high-risk groups, respectively. Continuous FRS, eGFR, and hepatitis C virus infection were independent risk factors for overall mortality. In our series, the FRS and eGFR at LT were able to predict the development of post-LT CVEs and poor outcomes. Liver Transpl 21:812-822, 2015. © 2015 AASLD.

Transfusion management and immunohematologic complications in liver transplantation: experience of a single institution.

OBJECTIVE: Liver transplantation (LT) has traditionally been associated with major blood loss and consequently high blood transfusion requirements. Our objective was to analyze transfusion management and incidence of immunohematologic complications in patients undergoing LT at our institution. METHODS: A retrospective analysis of immunohematologic events and transfusion outcomes was carried out at La Fe University Hospital in Valencia. Data from 654 patients were reviewed: 654 underwent only one LT while 36 underwent second LT. RESULTS: Patients received a median of 3 red blood cell (RBC) concentrates, 2 platelets concentrates (PCs) and 2 fresh frozen plasma units (FFPs). Variables significantly influencing RBC transfusions were: the MELD score, hemoglobin levels, and the platelet counts before LT. 27 patients (4.1%) had a positive antibody screening before transplant. Immunohematologic events occurred in 8% of the patients, mostly in the first month after LT, and involved hemolysis in 13 cases. Mortality was significantly higher in patients developing immunohematologic disorders (42.8 vs. 18.3%; p < 0.001). In the multivariable analysis, only ABO minor incompatibility between donor and recipient significantly increased the appearance of immunohematologic incidences (OR 4.92, 95% CI 2.31-10.50; p < 0.001). CONCLUSION: Transfusion management of patients that underwent LT can be complicated by immunohematologic problems. Blood banks should implement the DAT test in each transfusion to detect them.

Monosegment ALPPS: A new variant of the techniques for rapid hepatic regeneration. Critical review of the initial results of our series.

Associating Liver Partition and Portal vein ligation for Staged hepatectomy (ALPPS) is a novel surgical technique that provides fast and effective growth of liver remnant volume, allowing surgical resection of hepatic lesions initially considered unresectable. Short and long-term results and the convenience of carrying out this technique are issues that still remain under debate while waiting for the final outcomes of the multicenter registries with larger number of cases. The aim of this paper is to describe, from a critical point of view, the outcomes of the cases performed at our center (n=8). On the other hand, it is possible to leave only one hepatic segment as a liver remnant and we illustrate this new surgical procedure (ALPPS monosegment) performed in one patient.

Low RNA translation activit limits the efficacy of hydrodynamic gene transfer to pig liver in vivo.

BACKGROUND: Hydrodynamic gene delivery has proved an efficient strategy for nonviral gene therapy in the murine liver but it has been less efficient in pigs. The reason for such inefficiency remains unclear. The present study used a surgical strategy to seal the whole pig liver in vivo. METHODS: A solution of enhanced green fluorescent protein (eGFP) DNA was injected under two different venous injection conditions (anterograde and retrograde), employing flow rates of 10 and 20 ml/s in each case, with the aim of identifying the best gene transfer conditions. The gene delivery and information decoding steps were evaluated by measuring the eGFP DNA, mRNA and protein copy number 24 h after transfection. In addition, gold nanoparticles (diameters of 4 and 15 nm) were retrogradely injected (10 ml/s) to observe, by electron microscopy, the ability of the particle to access the hepatocyte. RESULTS: The gene delivery level was higher with anterograde injection, whereas the efficacy of gene expression was better with retrograde injection, suggesting differences in the decoding processes. Thus, retrograde injection mediates gene transcription (mRNA copy/cell) equivalent to that of intermediate expression proteins but the mRNA translation was lower than that of rare proteins. Electron microscopy showed that nanoparticles within the hepatocyte were almost exclusively 4 nm in diameter. CONCLUSIONS: The results suggest that the low activity of mRNA translation limits the final efficacy of the gene transfer procedure. On the other hand, the gold nanoparticles study suggests that elongated DNA conformation could offer advantages in that the access of 15-nm particles is very limited.