Natural rubber latex-based biomaterials for drug delivery and regenerative medicine: Trends and directions

Natural Rubber Latex (NRL) has shown to be a promising biomaterial for use as a drug delivery system to release various bioactive compounds. It is cost-effective, easy to handle, biocompatible, and exhibits pro-angiogenic and pro-healing properties for both soft and hard tissues. NRL releases compounds following burst and sustained release kinetics, exhibiting first-order release kinetics. Moreover, its pore density can be adjusted for tailored kinetics profiles. In addition, biotechnological applications of NRL in amblyopia, smart mattresses, and neovaginoplasty have demonstrated success. This comprehensive review explores NRL's diverse applications in biotechnology and biomedicine, addressing challenges in translating research into clinical practice. Organized into eight sections, the review emphasizes NRL's potential in wound healing, drug delivery, and metallic nanoparticle synthesis. It also addresses the challenges in enhancing NRL's physical properties and discusses its interactions with the human immune system. Furthermore, examines NRL's potential in creating wearable medical devices and biosensors for neurological disorders. To fully explore NRL's potential in addressing important medical conditions, we emphasize throughout this review the importance of interdisciplinary research and collaboration. In conclusion, this review advances our understanding of NRL's role in biomedical and biotechnological applications, offering insights into its diverse applications and promising opportunities for future development.

Mechanical and Optical Characterization of Single-shade Resin Composites Used in Posterior Teeth

OBJECTIVES

This study aimed to evaluate the optical and mechanical performance of two single-shade resin-based composites (RBCs) compared to those of a conventional RBC for restoring posterior teeth.

METHODS

Two single-shade RBCs, Omnichroma (Tukoyama) and Vittra Unique APS (FGM), and a conventional RBC, Filtek Z350XT shade A2 (3M Oral Care), were evaluated in this study. The optical shade-matching performance was measured using a spectrophotometer. The light emitted by VALO Grand (Ultradent) and transmitted through the 2.0-mm RBC specimens was evaluated using beam profiling. Knoop hardness (KH, N/mm2), degree of conversion (DC, %) at the top and bottom, flexural strength (FS, MPa), elastic modulus (E, GPa), postgel shrinkage (Shr, %), and shrinkage stress (MPa) were evaluated. Scanning electron microscopy (SEM) was used to characterize the filler. Data for FS, E, and Shr were analyzed by one-way analysis of variance (ANOVA) and KH and DC by repeated one-way ANOVA measurement followed by Tukey test (α=0.05). The modified von Mises stress values, light transmission, and SEM images were analyzed qualitatively.

RESULTS

All single-shade RBCs exhibited higher chromatic adaptation than the Filtek Z350XT (p<0.001). Omnichroma exhibited less color difference than Vittra Unique APS, irrespective of the shade. The light transmitted through Omnichroma and Vittra Unique APS increased during polymerization. KH and DC values were significantly reduced from the top to the bottom of the specimens for all RBCs (p<0.001); however, the ratio values were always higher than 80%. In general, all RBCs demonstrated similar mechanical properties. All RBCs exhibited a similar FS (p=0.083) and Shr value (p=0.144). Filtek Z350XT exhibited significantly higher E (p<0.001) than both single-shade RBCs. All RBCs exhibited similar shrinkage stress during restoration and similar residual stress during occlusal loading.

CONCLUSIONS

Single-shade Omnichroma and Vittra Unique APS increased light transmission during light-activation, demonstrating better chromatic adaptation than conventional Filtek Z350XT. In general, Omnichroma and Vittra Unique APS exhibited similar mechanical properties and shrinkage stress distributions as Filtek Z350XT during light-activation and occlusal loading.

Recent advances and perspectives on natural latex serum and its fractions for biomedical applications

Advances and the discovery of new biomaterials have opened new frontiers in regenerative medicine. These biomaterials play a key role in current medicine by improving the life quality or even saving the lives of millions of people. Since the 2000s, Natural Rubber Latex (NRL) has been employed as wound dressings, mechanical barrier for Guided Bone Regeneration (GBR), matrix for drug delivery, and grafting. NRL is a natural polymer that can stimulate cell proliferation, neoangiogenesis, and extracellular matrix (ECM) formation. Furthermore, it is well established that proteins and other biologically active molecules present in the Natural Latex Serum (NLS) are responsible for the biological properties of NRL. NLS can be obtained from NRL by three main methods, namely (i) Centrifugation (fractionation of NRL in distinct fractions), (ii) Coagulation and sedimentation (coagulating NRL to separate the NLS from rubber particles), and (iii) Alternative extraction process (elution from NRL membrane). In this review, the chemical composition, physicochemical properties, toxicity, and other biological information such as osteogenesis, vasculogenesis, adhesion, proliferation, antimicrobial behavior, and antitumoral activity of NLS, as well as some of its medical instruments and devices are discussed. The progress in NLS applications in the biomedical field, more specifically in cell cultures, alternative animals, regular animals, and clinical trials are also discussed. An overview of the challenges and future directions of the applications of NLS and its derivatives in tissue engineering for hard and soft tissue regeneration is also given.

Research Note: Antimicrobial resistance profile of Enterococcus spp. isolated from the eggshell of laying hens submitted to pharmacological treatment

The occurrence of antimicrobial resistance in microorganisms isolated from eggshells, especially Enterococcus, might serve as a parameter to assess the selection of bacteria due to the use of drugs in the diet of laying hens. In order to evaluate the frequency and the antimicrobial resistance profile of Enterococcus spp. isolated from the eggshells, 225 Hy-line laying hens were submitted to a 25-d long trial. The treatments were the following: hens fed ration without antimicrobials (control) and groups that received oxytetracycline (10 mg kg⁻¹), doxycycline (20 mg kg⁻¹), lincomycin (50 mg kg⁻¹), and enrofloxacin (10 mg kg⁻¹) in the ration for 5 d. Six replications were analyzed per treatment, composed of a pool of 5 eggs each. They were collected before treatment and on days 3, 6, 15, and 25, totaling 150 samples. Eggshells were submitted to counts of Enterococcus spp., which were identified by proteomic analyses. Antimicrobial resistance was determined by the disk-diffusion test. It was observed that 97.3% (n = 146) of the samples were contaminated with Enterococcus spp. There were no differences (P > 0.05) in the bacterial counts between treatments on the same day of evaluation. E. faecalis and E. faecium were the most frequent on the eggshells of all treatments. Multiresistance to the four classes of antimicrobials was also verified in the isolated bacteria. A total of 83% of the Enterococcus isolates showed resistance to neomycin, which was not administered to the hens, demonstrating an environmental problem. Thus, feeding laying hens with diets added with antimicrobials induces drug resistance in Enterococcus spp., isolated form the eggshells.

Análise da Resistência e da Interface de União de Procedimentos Adesivos Realizados no Esmalte Irradiado

O objetivo foi avaliar o efeito da radioterapia na resistência e na interface de união entre esmalte e compósito resinoso. Quarenta   e dois terceiros molares foram divididos aleatoriamente em três grupos (n14): Controle - não irradiado IrA - irradiado antes do procedimento restaurador e IrD - irradiado depois do procedimento restaurador. Os grupos irradiados foram submetidos à radiação de 70 Gy, 2 Gy/dia, 5 dias/semana, durante 7 semanas. Após hibridização do substrato, duas matrizes de tygon eram posicionadas sobre a superfície vestibular do esmalte e preenchidas com resina Filtek Z350 XT (3M ESPE). A avaliação da resistência de união (RU) foi feita por ensaio de microcisalhamento (0,5 mm/min). Para avaliar o padrão de falha, as amostras foram levadas em microscópio eletrônico de varredura (MEV). Dados de RU foram analisados com teste ANOVA One-way, seguido de Tukey (a0,05). Imagens obtidas em MEV foram analisadas descritivamente. ANOVA revelou diferença significativa entre os grupos (p<0,001). Tukey mostrou que o Controle e o IrD apresentaram os maiores valores de RU, sendo estatisticamente semelhantes (p0,716), enquanto o IrA teve os menores valores de RU se comparado aos demais (p≤0,001). Quanto ao padrão de falha, o Controle e o IrA apresentaram mais falhas adesivas (50% e 46,4%), enquanto no IrD houve um maior número de falhas coesivas em esmalte (39,3%), seguido de falhas adesivas (35,7%). Assim, justifica-se a aplicação clínica da restauração previamente a radioterapia, pois o momento da restauração interfere na RU do esmalte irradiado com o compósito.Palavras-chave: Esmalte. Radioterapia. Resistência ao Cisalhamento.

Potência Radiante, Irradiância e Espectro de Emissão de 22 Fontes de Fotoativação Utilizadas no Brasil

O trabalho mediu a potencia radiante, a irradiância e o espectro de emissão de 22 LCUs do mercado brasileiro. Foi medida a área das pontas (cm2) para calcular a irradiância a partir da potencia radiante (mW), que foi obtida por um medidor de potencia laser do laboratório. O MARC- Patient Simulator (MARC- PS) com espectrômetro de grau (USB4000, Ocean Optics) foi utilizado para medir o espectro no sensor anterior e posterior. Os dados foram analisados utilizando ANOVA two-way e os dados da potencia radiante foram analisados por ANOVA one-way seguida pelo teste de Tukey (a 0,05). Valo, Bluephase G2, Radii Plus mostrou irradiância semelhante na região anterior e posterior e ambos receberam irradiância maior que 500 mW / cm2. Seis LCUs apresentaram menor irradiância que a recomendada (500mW / cm2) quando usado na região posterior, KON-LUX, Altlux II, Biolux Standard, TL-01, Optilux 501, DX Turbo LED 1200 e duas LCUs quando foram usadas na região anterior KON-LUX e Altlux II. O Bluephase G2  e Optilight Max forneceram a maior potência e o KON-LUX, o Altlux II eo Biolux Standard mostraram as menores potências. O espectro das LCUs de pico único foi muito variável e das multi-picos emitiram espectro semelhante para ambos os sensores. O design, a potencia radiante, a irradiância e o tipo de LCUs são fatores que os clínicos e pesquisadores precisam ter domínio quando necessitam fotoativar materiais resinosos.Palavras-chave: Fontes de Luz. Potência. Irradiância. Espectro de Emissão no Simulador de Paciente de MARC.

Association between biomechanical alterations and migratory ability of semaphorin-3A-treated thymocytes

BACKGROUND

Class 3 semaphorins are soluble proteins involved in cell adhesion and migration. Semaphorin-3A (Sema3A) was initially shown to be involved in neuronal guidance, and it has also been reported to be associated with immune disorders. Both Sema3A and its receptors are expressed by most immune cells, including monocytes, macrophages, and lymphocytes, and these proteins regulate cell function. Here, we studied the correlation between Sema3A-induced changes in biophysical parameters of thymocytes, and the subsequent repercussions on cell function.

METHODS

Thymocytes from mice were treated in vitro with Sema3A for 30min. Scanning electron microscopy was performed to assess cell morphology. Atomic force microscopy was performed to further evaluate cell morphology, membrane roughness, and elasticity. Flow cytometry and/or fluorescence microscopy were performed to assess the F-actin cytoskeleton and ROCK2. Cell adhesion to a bovine serum albumin substrate and transwell migration assays were used to assess cell migration.

RESULTS

Sema3A induced filopodia formation in thymocytes, increased membrane stiffness and roughness, and caused a cortical distribution of the cytoskeleton without changes in F-actin levels. Sema3A-treated thymocytes showed reduced substrate adhesion and migratory ability, without changes in cell viability. In addition, Sema3A was able to down-regulate ROCK2.

CONCLUSIONS

Sema3A promotes cytoskeletal rearrangement, leading to membrane modifications, including increased stiffness and roughness. This effect in turn affects the adhesion and migration of thymocytes, possibly due to a reduction in ROCK2 expression.

GENERAL SIGNIFICANCE

Sema3A treatment impairs thymocyte migration due to biomechanical alterations in cell membranes.

Genetic diversity and relatedness between Canindé and British Alpine goat breeds in Northeastern Brazil accessed by microsatellite markers

The aim of this study was to access the genetic diversity and relatedness between Canindé and British Alpine goat breeds in the States of Piauí and Ceará using microsatellite markers. Genomic DNA was isolated from hair samples of 99 goats belonging to six different flocks. A panel of polymorphic heterologous microsatellite loci was used to genotype individuals. The microsatellite markers resulted in a total number of 145 alleles, with an average of 8.5 alleles per locus. The observed and expected heterozygosities were ≥0.687 and ≥0.627, respectively, for all loci. The polymorphic information content showed that all loci were highly informative with an overall mean of 0.757. Overall F_ST across all populations and loci was 18%, which was consistent with the coefficient of gene differentiation (G_ST = 0.104). AMOVA revealed that 12.8% of the variation was captured between breeds. The Bayesian STRUCTURE clustering detected the maximum likelihood for a model of two genetically distinct groups, in agreement with the number of predefined studied breeds and the two-dimensional plot from the PCoA analysis. The exotic British Alpine breed and the naturalized Brazilian Canindé breed were clearly differentiated by the microsatellite markers, indicating that these two breeds have distant genetic identities, despite the phenotypic similarity.

PLGA Implants containing vancomycin and dexamethasone: development, characterization and bactericidal effects

Post-operative endophthalmitis is an infection and an inflammation of the eye following a surgical procedure. Its treatment is based on drug injections into the eye. However, this treatment can lead to ocular complications. Intraocular implants could substitute the conventional therapy. Poly(lactic-co-glycolic acid) (PLGA) implants comprising on vancomycin and dexamethasone were evaluated as drug delivery system to treat endophthalmitis after cataract surgery. Implants were characterized by drug content uniformity, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Wide Angle X-ray Scattering (WAXS), Scanning Electron Microscopy (SEM) and in vitro drug release. The bactericidal effect of vancomycin, eluted from the implants, was demonstrated against Staphylococcus aureus and Staphylococcus epidermidis. The drugs were uniformly distributed in the polymer. The analytical techniques revealed the chemical integrity of the drugs incorporated into the polymer and the modification of dexamethasone semi-crystalline nature. Drugs were controlled released from implants; and the eluted vancomycin showed bactericidal effects. In conclusion, PLGA implants containing vancomycin and dexamethasone may represent a therapeutic alternative to treat post-operative endophthalmitis.

The recognition of Dendropsophus minusculus (Rivero, 1971) (Hylidae, Dendropsophini) as a highly polymorphic, multi-domain distributed species

Herein we present new occurrences of sites of Dendropsophus minusculus in Brazil adding information about reproductive biology and colour patterns of the species. Such information is fundamental for characterising the species that we believe has been neglected due to its morphological similarity with other congeneric species. Dendropsophus minusculus may be found in different morphoclimatic domains, being one of the most generalist species of the genus in this aspect. The species plasticity is not restricted to its occurrence, but also related to aspects of its reproductive biology, and we hypothesised that the latter feature could explain the wide geographical range of the species. We highlight the importance of further in-depth studies and the use of D. minusculus as a model to understand the historical events responsible for the current geographical distribution of the morphoclimatic domains in Brazil.

Analysis of acyclovir in vitreous humor by a validated HPLC method

An HPLC-UV method was developed and validated for the determination of acyclovir in vitreous humor. The method was carried out in isocratic mode using 0.02 mol/L acetic acid/methanol (95:5) as mobile phase, a C18 column at 25 degrees C and UV detection at 254 nm. The method was linear (r2> 0.99) over the range of 35-700 microg/mL, precise (RSD <5%), accurate (recovery ranged from 98.18 to 99.64%), robust, selective regarding of the vitreous humor, and robust remaining unaffected by deliberate variations in relevant parameters. The validated HPLC-UV method can be successfully applied to determine acyclovir directly injected into the vitreous cavity of rabbits' eye.

Bacillus thuringiensis var. israelensis production involving re-use of the supernatant

The supernatant arising after biomass separation of Bacillus thuringiensis var. israelensis by flocculation/sedimentation was re-used after being supplemented with 25, 50 and 75% (w/v) of the original culture medium, based on corn steep liquor, glucose and mineral salts. Supplementation at 75% gave a spore concentration (1 x 10(10) c.f.u. ml(-1)) five times greater than that obtained with the other supplements.

In vivo and in vitro effect of imipramine and fluoxetine on Na+,K+-ATPase activity in synaptic plasma membranes from the cerebral cortex of rats

The effects of in vivo chronic treatment and in vitro addition of imipramine, a tricyclic antidepressant, or fluoxetine, a selective serotonin reuptake inhibitor, on the cortical membrane-bound Na+,K+-ATPase activity were studied. Adult Wistar rats received daily intraperitoneal injections of 10 mg/kg of imipramine or fluoxetine for 14 days. Twelve hours after the last injection rats were decapitated and synaptic plasma membranes (SPM) from cerebral cortex were prepared to determine Na+,K+-ATPase activity. There was a significant decrease (10%) in enzyme activity after imipramine but fluoxetine treatment caused a significant increase (27%) in Na+,K+-ATPase activity compared to control (P<0.05, ANOVA; N = 7 for each group). When assayed in vitro, the addition of both drugs to SPM of naive rats caused a dose-dependent decrease in enzyme activity, with the maximal inhibition (60-80%) occurring at 0.5 mM. We suggest that a) imipramine might decrease Na+,K+-ATPase activity by altering membrane fluidity, as previously proposed, and b) stimulation of this enzyme might contribute to the therapeutic efficacy of fluoxetine, since brain Na+,K+-ATPase activity is decreased in bipolar patients.

[Progression to IDDM and islet cell antibodies (ICA; ICA-CF)]

We have followed eight first-degree relatives of IDDM patients (insulin-dependent, type I diabetes) attending the outpatient diabetes clinic at the State University of Rio de Janeiro for three years, all of them with positive islet cell antibodies (ICA and/or ICA-CF). Three out of eight relatives less than fifteen years old have subsequently progressed to overt Insulin-Dependent Diabetes Mellitus (IDDM) 12, 21 and 8 months after the first positive autoantibodies detection. Four relatives have remained with ICA and/or ICA-CF positive, and in another one the reaction became negative during the observation period. A positive correlation has been found between high titles of ICA (> or = 1/16) and development of IDDM. We have concluded from our prospective study during three years that of our antibody-positive relatives, 37.5 % have developed overt diabetes, all of them being less than fifteen years old, with high titles of ICA and ICA-CF positive.

Cloxacillin-induced acute tubulo interstitial nephritis

OBJECTIVE

To report a case of possible cloxacillin-induced acute tubulo interstitial nephritis (AIN).

CASE SUMMARY

A 15-year-old male patient presented with hypertension, edema, lumbar pain, sterile pyuria, eosinophiluria (ten percent), and severe renal dysfunction three months after the ingestion of cloxacillin. A renal biopsy revealed diffuse edema and inflammatory infiltrate of the interstitium (five percent eosinophils). He received four sessions of peritoneal dialysis with dramatic improvement in urinary output and renal function. His biochemical parameters returned to normal values 21 days after admission, without the use of glucocorticosteroids.

DISCUSSION

Published case reports on AIN induced by penicillin and related drugs are reviewed and compared. The role of interstitial edema in acute renal failure associated with drug-induced AIN is mentioned.

CONCLUSIONS

AIN is a rare but significant complication of therapy with penicillin and related drugs. The clinical picture is similar for all of these drugs, but skin rash and fever are absent in AIN induced by cloxacillin and cloxacillin-related drugs. Dialysis improved the patient's urinary output and renal function. Beta-lactam antibiotics should be avoided in patients with cloxacillin-induced AIN.