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2.
Trends Plant Sci ; 29(9): 1029-1040, 2024 Sep.
Article in English | MEDLINE | ID: mdl-38641475

ABSTRACT

Understanding the complex relationships between plants, their microbiomes, and environmental changes is crucial for improving growth and survival, especially for long-lived tree species. Trees, like other plants, maintain close associations with a multitude of microorganisms on and within their tissues, forming a 'holobiont'. However, a comprehensive framework for detailed tree-microbiome dynamics, and the implications for climate adaptation, is currently lacking. This review identifies gaps in the existing literature, emphasizing the need for more research to explore the coevolution of the holobiont and the full extent of climate change impact on tree growth and survival. Advancing our knowledge of plant-microbial interactions presents opportunities to enhance tree adaptability and mitigate adverse impacts of climate changes on trees.


Subject(s)
Climate Change , Microbiota , Trees , Microbiota/physiology , Trees/microbiology , Trees/growth & development , Trees/physiology
3.
Res Sq ; 2024 Mar 15.
Article in English | MEDLINE | ID: mdl-38559201

ABSTRACT

Purpose: Monotherapy with vancomycin or daptomycin remains guideline-based care for methicillin-resistant Staphylococcus aureus bacteremia (MRSA-B) despite concerns regarding efficacy. Limited data support potential benefit of combination therapy with ceftaroline as initial therapy. We present an assessment of outcomes of patients initiated on early combination therapy for MRSA-B. Methods: This was a single-center, retrospective study of adult patients admitted with MRSA-B between July 1, 2017 and April 31, 2023. During this period, there was a change in institutional practice from routine administration of monotherapy to initial combination therapy for most patients with MRSA-B. Combination therapy included vancomycin or daptomycin plus ceftaroline within 72 hours of index blood culture and monotherapy was vancomycin or daptomycin alone. The primary outcome was a composite of persistent bacteremia, 30-day all-cause mortality, and 30-day bacteremia recurrence. Time to microbiological cure and safety outcomes were assessed. All outcomes were assessed using propensity score-weighted logistic regression. Results: Of 213 patients included, 118 received monotherapy (115 vancomycin, 3 daptomycin) and 95 received combination therapy with ceftaroline (76 vancomycin, 19 daptomycin). The mean time from MRSA-positive molecular diagnostic blood culture result to combination therapy was 12.1 hours. There was no difference between groups for the primary composite outcome (OR 1.58, 95% CI 0.60, 4.18). Time to microbiological cure was longer with combination therapy (mean difference 1.50 days, 95% CI 0.60, 2.41). Adverse event rates were similar in both groups. Conclusions: Early initiation of ceftaroline-based combination therapy did not improve outcomes for patients with MRSA-B in comparison to monotherapy therapy.

4.
Ann R Coll Surg Engl ; 2024 Apr 25.
Article in English | MEDLINE | ID: mdl-38660827

ABSTRACT

INTRODUCTION: Surgical care practitioners (SCPs) are non-medical workers involved in various aspects of the management of surgical patients. The role includes assisting and performing surgical procedures. More than 60,000 laparoscopic cholecystectomies (LC) are performed annually in the UK. With ever-increasing pressure on waiting lists, it is important to look at fully utilising the skills of our entire workforce. We report what we believe is the first published series of LC performed by an SCP. METHODS: A retrospective review of a prospectively collected database was performed. The primary outcome was any complication requiring intervention. Secondary outcomes were minor complications, operative time, length of stay, conversion and readmission. RESULTS: In total, 170 patients were operated on. Indications were biliary colic in 127 (74.7%), cholecystitis in 30 (17.6%) and pancreatitis in 13 (7.6%). Mean operating time was 65min (range 35-152min). Fifty-three operations were assisted by a consultant, 110 by a specialist or associate specialist grade (SAS) doctor and 7 by a core trainee (CT2). Some 139 (81.7%) patients were discharged on the day of surgery and 24 (14.1%) stayed one night in hospital. There were no major complications. Five patients required readmission, three with pain and two with port site infections. There were no conversions or transfusions required. CONCLUSIONS: There is a paucity of published data on surgical outcomes of procedures performed by SCPs. With a structured, supervised approach, SCPs could be trained to take on more complex procedures and further strengthen the surgical workforce. This study demonstrates that elective LC can be safely performed by an appropriately trained and supervised SCP.

5.
ACS Med Chem Lett ; 15(1): 149-155, 2024 Jan 11.
Article in English | MEDLINE | ID: mdl-38229742

ABSTRACT

Pseudomonas aeruginosa (PA), a Gram-negative pathogen, is a common cause of nosocomial infections, especially in immunocompromised and cystic fibrosis patients. PA is intrinsically resistant to many currently prescribed antibiotics due to its tightly packed, anionic lipopolysaccharide outer membrane, efflux pumps, and ability to form biofilms. PA can acquire additional resistance through mutation and horizontal gene transfer. PA ATP synthase is an attractive target for antibiotic development because it is essential for cell survival even under fermentation conditions. Previously, we developed two lead quinoline compounds that were capable of selectively inhibiting PA ATP synthase and acting as antibacterial agents against multidrug-resistant PA. Herein we conduct a structure-activity relationship analysis of the lead compounds through the synthesis and evaluation of 18 quinoline derivatives. These compounds function as new antibacterial agents while providing insight into the balance of physical properties needed to promote cellular entry while maintaining PA ATP synthase inhibition.

6.
Perspect Public Health ; 144(1): 14-17, 2024 01.
Article in English | MEDLINE | ID: mdl-38156477

Subject(s)
Hunger , Humans , Sudan
7.
Pediatr Clin North Am ; 67(5): 995-1009, 2020 10.
Article in English | MEDLINE | ID: mdl-32888694

ABSTRACT

Artificial intelligence (AI) in the last decade centered primarily around digitizing and incorporating the large volumes of patient data from electronic health records. AI is now poised to make the next step in health care integration, with precision medicine, imaging support, and development of individual health trends with the popularization of wearable devices. Future clinical pediatric cardiologists will use AI as an adjunct in delivering optimum patient care, with the help of accurate predictive risk calculators, continual health monitoring from wearables, and precision medicine. Physicians must also protect their patients' health information from monetization or exploitation.


Subject(s)
Algorithms , Artificial Intelligence , Cardiology/methods , Precision Medicine/methods , Child , Electronic Health Records , Humans
8.
Pediatr Emerg Care ; 36(10): e573-e575, 2020 Oct.
Article in English | MEDLINE | ID: mdl-29298252

ABSTRACT

OBJECTIVES: Adolescents who seek care in emergency departments (EDs) are often at high risk for sexually transmitted infections (STIs). The objective of this study was to assess adolescent attitudes toward ED-based STI screening. METHODS: We conducted a secondary analysis of a cross-sectional study that evaluated STI screening acceptability and prevalence when STI testing was universally offered to asymptomatic adolescents presenting to the ED for care. Adolescents 14 to 21 years old completed a computerized survey and answered questions regarding attitudes toward ED-based STI screening and sexual behavior. We performed multivariable logistic regression to compare differences in attitudes toward ED-based STI screening among patients who agreed versus declined STI testing. RESULTS: Of 553 adolescents, 326 (59.0%) agreed to be tested for STIs. Most (72.1%) believed the ED was an appropriate place for STI screening. Patients who agreed to be tested for STIs were more likely to positively endorse ED-based STI screening than those who declined STI testing [77.0% vs 64.8%; adjusted odds ratios, 1.6; 95% confidence interval (CI), 1.1-2.4]. Most (82.6%) patients stated they would feel comfortable getting tested for STIs in the ED. There was no difference in the comfort level of ED-based STI testing between those who agreed and declined STI testing (83.5% vs 81.4%; adjusted odds ratios, 1.1; 95% CI, 0.7-1.8). CONCLUSION: Our results suggest that adolescents view the ED as an acceptable location for STI screening. Therefore, the ED may serve a role in increasing the accessibility of STI detection and prevention resources for adolescents.


Subject(s)
Attitude to Health , Emergency Service, Hospital , Mass Screening/psychology , Sexually Transmitted Diseases/diagnosis , Adolescent , Cross-Sectional Studies , Female , Humans , Male , Young Adult
9.
Cardiol Young ; 29(1): 88-89, 2019 Jan.
Article in English | MEDLINE | ID: mdl-30378525

ABSTRACT

We present a pilot case using an innovative fusion of echocardiogram and MRI achieved with a MATLAB-based imaging programme to explore the feasibility of this imaging strategy in the functional and anatomic assessment of a patient with repaired tetralogy of Fallot requiring pulmonary valve intervention. Echocardiogram and MRI neutralises the disadvantages and limitations of each individual imaging modality and yields important anatomic and haemodynamic information crucial to the treatment decision-making process. Future image fusion strategies can apply to three-dimensional images and image-directed therapy for CHD.


Subject(s)
Echocardiography/methods , Magnetic Resonance Imaging/methods , Pulmonary Valve Insufficiency/diagnostic imaging , Pulmonary Valve Insufficiency/surgery , Tetralogy of Fallot/complications , Adolescent , Heart Valve Prosthesis Implantation , Humans , Male , Pulmonary Valve/surgery , Tetralogy of Fallot/surgery
10.
Am Surg ; 84(5): 615-619, 2018 May 01.
Article in English | MEDLINE | ID: mdl-29966558

ABSTRACT

Diverting loop ileostomies are common procedures for protecting high-risk anastomoses. There is little consensus on the most ideal technique both in terms of cost efficiency and outcome. Data for this study were collected from 101 patients who underwent loop ileostomy reversal between 2009 and 2014 at Morristown Medical Center. Of the 101 patients included in the review, 57 received a hand-sewn anastomosis (HS-A) and 44 received a stapled anastomosis (S-A). Average total hospital charges for stapled anastomoses were significantly greater than that for hand-sewn anastomoses, as were total operating room supply costs. When the total cost of the operation itself was considered, S-A cases were still found to be significantly greater than HS-A cases. Hospital room charges, total lab charges, pathology charges, and EKG/ECG charges were all greater for S-A cases than HS-A cases. Overall costs were greater for S-As than hand-sewn anastomoses and because of a lack of difference in procedure length, stapler supply costs were not offset. Complication rates and length of stay were also similar between the techniques. We found S-A cases to be more costly and have a greater cost/hour than HS-A cases.


Subject(s)
Hospital Charges/statistics & numerical data , Hospital Costs/statistics & numerical data , Ileostomy/economics , Suture Techniques/economics , Adult , Anastomosis, Surgical/economics , Anastomosis, Surgical/methods , Female , Humans , Ileostomy/methods , Male , Middle Aged , New Jersey , Reoperation/economics , Retrospective Studies , Surgical Stapling/economics
12.
J Bone Joint Surg Am ; 99(2): 99-105, 2017 Jan 18.
Article in English | MEDLINE | ID: mdl-28099299

ABSTRACT

BACKGROUND: The direct anterior approach for total hip arthroplasty (THA) is marketed with claims of superiority over other approaches. Femoral exposure can be technically challenging and potentially lead to early failure. We examined whether surgical approach is associated with early THA failure. METHODS: A retrospective review of 478 consecutive early revision THAs performed within 5 years after the primary THAs at 3 academic centers from 2011 through 2014 was carried out. Exclusion criteria resulted in a final analysis sample of 342 early-failure THAs. The surgical approach of the primary operation that was revised, the time to the revision, and the etiology of the failure leading to the revision were documented. RESULTS: Analysis of the revisions due to early femoral failure showed them to be more common in patients who had undergone the direct anterior approach (57/112; 50.9%) than in those treated with the direct lateral (39/112; 34.8%) or the posterior (16/112; 14.3%) approach (p = 0.001). In multivariate regression analysis controlling for age, sex, laterality, Dorr bone type, body mass index (BMI) at revision, bilateral procedure (yes/no), and femoral stem type, the direct anterior approach remained a significant predictor of early femoral failure (p = 0.007). The majority of early revisions due to instability were associated with the posterior (19/40; 47.5%) or direct anterior (15/40; 37.5%) approach (p = 0.001 for the comparison with the direct lateral approach [6/40; 15.0%]). CONCLUSIONS: Despite claims of earlier recovery and improved outcomes with the direct anterior approach for THA, our findings indicate that that approach may confer a greater risk of early femoral failure and, along with the posterior approach, confer a greater risk of early instability compared with the direct lateral approach. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.


Subject(s)
Arthroplasty, Replacement, Hip/methods , Hip Prosthesis , Prosthesis Failure/etiology , Acetabulum/injuries , Arthroplasty, Replacement, Hip/adverse effects , Bone Cements , Female , Femoral Fractures/etiology , Femoral Fractures/surgery , Fractures, Bone/etiology , Fractures, Bone/surgery , Humans , Male , Middle Aged , Periprosthetic Fractures/etiology , Postoperative Complications/etiology , Reoperation/statistics & numerical data , Retrospective Studies , Risk Factors
13.
J Surg Educ ; 73(5): 844-50, 2016.
Article in English | MEDLINE | ID: mdl-27321982

ABSTRACT

BACKGROUND: With the introduction of stapling devices (SDs), the proportion of hand-sewn (HS) intestinal anastomoses (IAs) has declined. As more IAs are constructed with SDs, there are fewer opportunities for general surgery residents (GSRs) to acquire the skills for HS techniques during their training. STUDY DESIGN: Data for this study were extracted from an existing database of all IAs performed at the Department of Surgery of the Morristown Medical Center since 2003. For the purposes of this study, a 5.5-year timeframe was used between July 2006 and 2011, which contained 1659 IA operations on adult patients with resident involvement. GSRs of the 5-year general surgery residency program were grouped by postgraduate year (PGY) for further analysis. RESULTS: The number of all IAs created by each resident during the 5-year training was 67.2 on average. Most of these operations were done in the last 2 years of the training: 45.1% of all IAs in PGY5 and 37.3% of all IAs in PGY4. Of all, 1659 IAs performed in the study period, 711 (42.9% of total) were done laparoscopically and 948 (57.1% of all IAs) were done as open operations. Laparoscopic operations had a proportionally higher rate of SD use when compared to open cases (90.9% vs 82.4%). On average, each resident constructed 9.4 HS IAs (13.98% of all IAs) and 57.8 SD IAs (86.02% of total). Out of all anastomoses, ostomy reversals (30.7%) had the highest percentage of HS suturing followed by right colectomies (27.5%), ileal pouch-anal anastomoses and total colectomies and proctocolectomies (23.3%), small bowel resection (17.0%), and left colectomies (5.5%). Regardless of the location of the operation, stapled and sutured anastomoses had similar outcomes measured by the rate of anastomotic leaks. Residents used significantly more SDs in the creation of anastomoses than HS suturing in the PGY3, PGY4, and PGY5 years. We also documented that attending surgeons who are older more often used HS suturing than their younger colleagues when creating IAs. CONCLUSIONS: The experiences of GSRs in IA operations are heavily weighted toward the use of SDs. There are select cases, however, when HS suturing can have an advantage over stapler use in anastomosis creation. Therefore, we believe that GSRs should continue learning, perfecting, and using the both techniques.


Subject(s)
Anastomosis, Surgical/education , Clinical Competence , Colonic Diseases/surgery , Education, Medical, Graduate , General Surgery/education , Intestine, Small/surgery , Humans , Internship and Residency , Laparoscopy/education , Surgical Stapling , Suture Techniques
14.
BMC Med Imaging ; 16: 34, 2016 Apr 27.
Article in English | MEDLINE | ID: mdl-27121379

ABSTRACT

BACKGROUND: Post mortem imaging is playing an increasingly important role in perinatal autopsy, and correct interpretation of imaging changes is paramount. This is particularly important following intra-uterine fetal death, where there may be fetal maceration. The aim of this study was to investigate whether any changes seen on a whole body fetal post mortem magnetic resonance imaging (PMMR) correspond to maceration at conventional autopsy. METHODS: We performed pre-autopsy PMMR in 75 fetuses using a 1.5 Tesla Siemens Avanto MR scanner (Erlangen, Germany). PMMR images were reported blinded to the clinical history and autopsy data using a numerical severity scale (0 = no maceration changes to 2 = severe maceration changes) for 6 different visceral organs (total 12). The degree of maceration at autopsy was categorized according to severity on a numerical scale (1 = no maceration to 4 = severe maceration). We also generated quantitative maps to measure the liver and lung T2. RESULTS: The mean PMMR maceration score correlated well with the autopsy maceration score (R(2) = 0.93). A PMMR score of ≥4.5 had a sensitivity of 91%, specificity of 64%, for detecting moderate or severe maceration at autopsy. Liver and lung T2 were increased in fetuses with maceration scores of 3-4 in comparison to those with 1-2 (liver p = 0.03, lung p = 0.02). CONCLUSIONS: There was a good correlation between PMMR maceration score and the extent of maceration seen at conventional autopsy. This score may be useful in interpretation of fetal PMMR.


Subject(s)
Fetus/pathology , Magnetic Resonance Imaging/methods , Autopsy , Fetal Death , Humans , Liver/pathology , Lung/pathology , Magnetic Resonance Imaging/instrumentation
15.
Ann Biomed Eng ; 44(7): 2103-13, 2016 07.
Article in English | MEDLINE | ID: mdl-26577256

ABSTRACT

We have recently developed a bioreactor that can apply both shear and compressive forces to engineered tissues in dynamic culture. In our system, alginate hydrogel beads with encapsulated human mesenchymal stem cells (hMSCs) were cultured under different dynamic conditions while subjected to periodic, compressive force. A customized pressure sensor was developed to track the pressure fluctuations when shear forces and compressive forces were applied. Compared to static culture, dynamic culture can maintain a higher cell population throughout the study. With the application of only shear stress, qRT-PCR and immunohistochemistry revealed that hMSCs experienced less chondrogenic differentiation than the static group. The second study showed that chondrogenic differentiation was enhanced by additional mechanical compression. After 14 days, alcian blue staining showed more extracellular matrix formed in the compression group. The upregulation of the positive chondrogenic markers such as Sox 9, aggrecan, and type II collagen were demonstrated by qPCR. Our bioreactor provides a novel approach to apply mechanical forces to engineered cartilage. Results suggest that a combination of dynamic culture with proper mechanical stimulation may promote efficient progenitor cell expansion in vitro, thereby allowing the culture of clinically relevant articular chondrocytes for the treatment of articular cartilage defects.


Subject(s)
Antigens, Differentiation/biosynthesis , Cell Culture Techniques/methods , Cell Proliferation , Chondrogenesis , Compressive Strength , Gene Expression Regulation , Mesenchymal Stem Cells/metabolism , Humans , Mesenchymal Stem Cells/cytology
16.
Clin Radiol ; 70(8): 872-80, 2015 Aug.
Article in English | MEDLINE | ID: mdl-26050535

ABSTRACT

AIM: To compare the diagnostic accuracy of non-invasive cerebral post-mortem magnetic resonance imaging (PMMRI) specifically for cerebral and neurological abnormalities in a series of fetuses and children, compared to conventional autopsy. MATERIALS AND METHODS: Institutional ethics approval and parental consent was obtained. Pre-autopsy cerebral PMMRI was performed in a sequential prospective cohort (n = 400) of fetuses (n = 277; 185 ≤ 24 weeks and 92 > 24 weeks gestation) and children <16 years (n = 123) of age. PMMRI and conventional autopsy findings were reported blinded and independently of each other. RESULTS: Cerebral PMMRI had sensitivities and specificities (95% confidence interval) of 88.4% (75.5 to 94.9), and 95.2% (92.1 to 97.1), respectively, for cerebral malformations; 100% (83.9 to 100), and 99.1% (97.2 to 99.7) for major intracranial bleeds; and 87.5% (80.1 to 92.4) and 74.1% (68 to 79.4) for overall brain pathology. Formal neuropathological examination was non-diagnostic due to maceration/autolysis in 43/277 (16%) fetuses; of these, cerebral PMMRI imaging provided clinically important information in 23 (53%). The sensitivity of PMMRI for detecting significant ante-mortem ischaemic injury was only 68% (48.4 to 82.8) overall. CONCLUSIONS: PMMRI is an accurate investigational technique for identifying significant neuropathology in fetuses and children, and may provide important information even in cases where autolysis prevents formal neuropathological examination; however, PMMRI is less sensitive at detecting hypoxic-ischaemic brain injury, and may not detect rarer disorders not encountered in this study.


Subject(s)
Autopsy/methods , Brain Diseases/diagnosis , Brain/abnormalities , Fetus/abnormalities , Magnetic Resonance Imaging/methods , Adolescent , Child , Child, Preschool , Humans , Hypoxia-Ischemia, Brain/diagnosis , Infant , Infant, Newborn , Intracranial Hemorrhages/diagnosis , Prospective Studies , Sensitivity and Specificity
17.
Br J Radiol ; 87(1036): 20130621, 2014 Apr.
Article in English | MEDLINE | ID: mdl-24288400

ABSTRACT

Although post-mortem MRI (PMMR) was proposed as an alternative to conventional autopsy more than a decade ago, the lack of systematic validation has limited its clinical uptake. Minimally invasive autopsy (MIA) using PMMR together with ancillary investigations has now been shown to be as accurate as conventional autopsy in foetuses, newborns and infants and is particularly useful for cerebral, cardiac and genitourinary imaging. Unlike conventional autopsy, PMMR provides a permanent three-dimensional auditable record, with accurate estimation of internal organ volumes. MIA is becoming highly acceptable to parents and professionals, and there is widespread political support and public interest in its clinical implementation in the UK. In the short to medium term, it is desirable that a supraregional network of specialist centres should be established to provide this service within the current National Health Service framework.


Subject(s)
Autopsy , Magnetic Resonance Imaging , Autopsy/methods , Autopsy/standards , Child , Fetal Death/pathology , Fetus , Humans , Infant , Infant, Newborn , Magnetic Resonance Imaging/methods , Organ Size , Whole Body Imaging/methods
18.
J Biomater Sci Polym Ed ; 24(8): 912-26, 2013.
Article in English | MEDLINE | ID: mdl-23647248

ABSTRACT

Thiolated polymers containing disulfide linkages are commonly researched in gene delivery with the assumption that the thiolated complexes form disulfide bonds. This study investigates the extent of disulfide linking in a thiol-containing polymer and determines the impact that free thiols have on the polymer's delivery potential. A fluorescent cationic polymer containing thiol pendant chains was prepared from poly(allylamine) and 2-iminothiolate (Traut's reagent). Polymer fluorescence was determined by UV plate readings and fluorescent microscopy. Transfection efficiency and cytotoxicity were assessed in MCF-7 breast cancer cells. Results show that thiolated polymers exhibited fluorescence at ex/em ∼595/620. Fluorescent measurements, microscopy imaging, and DNA electrophoresis show that thiolated polymers are not internalized by cells in a culture, yet, they bind to the cell surface, perhaps valuable for applications requiring cell adhesion.


Subject(s)
Dithionitrobenzoic Acid/chemistry , Gene Transfer Techniques , Imidoesters/chemistry , Polyamines/chemistry , Cell Count , Cell Line , Cell Membrane/metabolism , DNA/chemistry , DNA/genetics , Humans , Protein Binding , Transfection
19.
J Matern Fetal Neonatal Med ; 25(11): 2467-9, 2012 Nov.
Article in English | MEDLINE | ID: mdl-22765762

ABSTRACT

OBJECTIVE: We examined the yield and quality of genomic deoxyribonucleic acid (DNA) extracted from various postmortem fetal tissues. METHODS: Fetal tissues were collected at the time of autopsy, and DNA was subsequently extracted. The yield and DNA quality was assessed using ultraviolet spectrometry and agarose gel electrophoresis. We used polymerase chain reaction (PCR) to assess the DNA extracted for genomic testing. RESULTS: The median (range) gestation of the fetuses was 22 (16-41) weeks and the postmortem interval was 5.5 (2-10) days. Non-degraded genomic DNA was successfully extracted from all fetal tissues. Liver tissue had the lowest quality and muscle the highest quality. DNA yield or purity was not influenced by the postmortem interval. CONCLUSION: High quality genomic DNA can be extracted from fetal muscle, despite postmortem intervals of several days.


Subject(s)
Autopsy , DNA/isolation & purification , Fetus/chemistry , Genetic Testing/standards , Efficiency , Fetus/metabolism , Genome, Human , Gestational Age , Heart/embryology , Humans , Kidney/chemistry , Kidney/embryology , Kidney/metabolism , Kidney/pathology , Liver/chemistry , Liver/embryology , Liver/metabolism , Liver/pathology , Muscles/chemistry , Muscles/embryology , Muscles/metabolism , Muscles/pathology , Myocardium/chemistry , Myocardium/metabolism , Myocardium/pathology , Polymerase Chain Reaction/methods , Quality Control
20.
Biomacromolecules ; 13(5): 1331-9, 2012 May 14.
Article in English | MEDLINE | ID: mdl-22515194

ABSTRACT

Polymers have attracted much attention as potential gene delivery vectors due to their chemical and structural versatility. However, several challenges associated with polymeric carriers, including low transfection efficiencies, insufficient cargo release, and high cytotoxicity levels have prevented clinical implementation. Strong electrostatic interactions between polymeric carriers and DNA cargo can prohibit complete cargo release within the cell. As a result, cargo DNA never reaches the cell's nucleus where gene expression takes place. In addition, highly charged cationic polymers have been correlated with high cytotoxicity levels, making them unsuitable carriers in vivo. Using poly(allylamine) (PAA) as a model, we investigated how pH-sensitive disulfide cross-linked polymer networks can improve the delivery potential of cationic polymer carriers. To accomplish this, we conjugated thiol-terminated pendant chains onto the primary amines of PAA using 2-iminothiolane, developing three new polymer vectors with 5, 13, or 20% thiol modification. Unmodified PAA and thiol-conjugated polymers were tested for their ability to bind and release plasmid DNA, their capacity to protect genetic cargo from enzymatic degradation, and their potential for endolysosomal escape. Our results demonstrate that polymer-plasmid complexes (polyplexes) formed by the 13% thiolated polymer demonstrate the greatest delivery potential. At high N/P ratios, all thiolated polymers (but not unmodified counterparts) were able to resist decomplexation in the presence of heparin, a negatively charged polysaccharide used to mimic in vivo polyplex-protein interactions. Further, all thiolated polymers exhibited higher buffering capacities than unmodified PAA and, therefore, have a greater potential for endolysosomal escape. However, 5 and 20% thiolated polymers exhibited poor DNA binding-release kinetics, making them unsuitable carriers for gene delivery. The 13% thiolated polymers, on the other hand, displayed high DNA binding efficiency and pH-sensitive release.


Subject(s)
DNA/chemistry , Gene Transfer Techniques , Genetic Vectors/chemistry , Polyamines/chemistry , Sulfhydryl Compounds/chemistry , Binding Sites , Plasmids/chemistry
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