Polimery w medycynie最新文献

Background: The biological half life of metformin requires multiple doses which are associated with poor patient compliance. This justifies the need for a dosage form with reduced dosing frequency.

Objectives: Gums from Enterolobium cyclocarpum and Cedrela odorata trees were evaluated in formulating bioadhesive microspheres containing metformin hydrochloride, for sustained drug release. Hydroxylpropylmethyl cellulose (HPMC) was the standard.

Material and methods: Microspheres were produced from formulations of API and either cedrela gum (FC), enterolobium gum (FE) or HPMC (FH), using a W/O solvent extraction technique. The microspheres were characterized using a particle size analyzer, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), powder X-ray diffractometer (PXRD), drug entrapment, in vitro release and mucoadhesion studies. The data was analyzed using ANOVA and t-test at p = 0.05.

Results: FT-IR spectroscopy indicated no alteration in the functional groups of metformin. A yield of 92-98% microspheres was obtained from all the formulations which had a particle size range of 72-84 μm. SEM revealed cylindrical to near-spherical particles with rough surfaces. The drug release profile showed a burst over the first 30 min followed by a steady release for about 5 h and a slow release for 5 days. Formulations containing the gums sustained the release of API for almost the same time as HPMC formulations; the ranking order was FE > FH > FC (p > 0.05). All the formulations exhibited good concentration-dependent mucoadhesive properties.

Conclusions: The gums were suitable for formulation of mucoadhesive microspheres for sustained release of metformin. The formulations showed good release properties in an alkaline pH.

Background: Hydrophilic polymers provide a means of sustaining drug delivery. Native gums may be limited in function, but modification may improve their activity.

Objectives: The aim of the study was to evaluate native and modified forms of Terminalia mantaly gum for their sustained-release and bioadhesive properties.

Material and methods: The native gum (NTM) was modified by microwave irradiation for 20 seconds (MTM20) and 60 seconds (MTM60) and characterized using microscopy, Fourier transform infrared spectroscopy (FTIR) and packing properties. The effects of the thermally induced molecular reorientation were determined. Tablet formulations of naproxen were produced by direct compression. The mechanical, bioadhesive and release properties of the formulations were determined.

Results: Irradiation of NTM improved the gum's flow properties, resulting in Carr's Index and Hausner's ratios lower than 16% and 1.25, respectively. Swelling studies showed that MTM20 and MTM60 had lower water absorption capacity and swelling index values, while packing properties improved upon irradiation, as depicted by lower tapped density values. FTIR spectra of samples showed that the irradiated gums were distinct from the native gums and did not interact with naproxen sodium. The gum's mechanical properties improved with MTM20 and MTM60 and sustained-release action of up 12 h was obtained.

Conclusions: Inclusion of hydroxypropyl methylcellulose (HPMC) in the tablet formulations proved critical for bioadhesion. Microwave irradiation of native Terminalia mantaly gum improved the flow, mechanical and sustained-release properties of Naproxen tablets, and the addition of HPMC increased bioadhesion properties. The tablet properties of the native gum were significantly improved after 20 s of microwave irradiation.

For many years, research has been carried out on finding an ideal bone substitute. Chitosan (CTS) is a naturally occurring polysaccharide, obtained mainly from, inter alia, the shells of crustaceans. It is characterized by its high level of biocompatibility, biodegradability and antimicrobial properties as well as its support in the healing of wounds. Chitosan, due to its ability to form porous structures, can be used in the production of scaffolds used in the treatment of bone defects. There are numerous studies on the use of CTS in combination with other substances which aim to improve its biological and mechanical properties. The combination of chitosan with the calcium phosphate hydroxyapatite (HAp) has been extensively tested. The objective of the current studies is to verify the properties of scaffolds consisting of chitosan and other substances like polybutylene succinate, human bone marrow mesenchymal stem cells (hBMSCs), collagen, alginate, transforming growth factor - β (TGF-β), insulin-like growth factor (IGF), platelet-derived growth factor (PDGF) or bone morphogenetic proteins (BMP). The aim of the current research is to develop a scaffold with sufficiently good mechanical properties. Trials are underway with many of the biological and synthetic components affecting the biological properties of chitosan. This will allow for the creation of a substitute that fully meets the conditions for an ideal artificial bone.

Background: Natural polymers such as gums have gained attention in drug delivery systems due to their availability, compatibility and degradation under natural and physiological conditions.

Objectives: The aim of the present study was to investigate the film forming properties of gums obtained from the stem of Cissus polpunea (Guill and Perr) and the seed of Irvingia gabonensis (O'Rorke).

Material and methods: Gums were extracted from the relevant plant parts and characterized using functional, proximate and elemental properties. Films were prepared by the casting method using gum concentrations of 1-4% w/v and varied with propylene glycol (PG). The films were assessed through physical observation, thickness, swelling power and moisture sorption effects using the relative humidity of 0, 27, 43, 57, 75 and 90%. The gum yielding optimal film properties was used as coating material in ibuprofen tablet formulations. The mechanical and release properties of the tablets were determined.

Results: The functional and proximate properties of gums showed a similarity in the majority of the parameters, but significant (p < 0.05) variation existed in their solubility, while elemental assessment revealed the absence of toxic metals. Generally, the films were homogenous, opaque and demonstrated high swelling power in phosphate buffer, which was pH-dependent. Moisture sorption properties of the gums increased with the increase in relative humidity in the order HPMC < Cissus < Irvingia. Film-coated ibuprofen tablets showed higher mechanical properties and disintegration and dissolution times compared with uncoated tablets.

Conclusions: Cissus and irvingia gums have demonstrated acceptable functional, proximate and elemental properties. Film-coated ibuprofen tablets showed higher mechanical and release properties than was the case in uncoated tablets.

Chitin is a natural polysaccharide commonly found in nature and chitosan is its partially deacetylated derivative. The properties of both biopolymers allow their wide use in medicine and various industries. This paper presents the possibilities offered by chitin and chitosan for the creation of neurotubes utilized in peripheral nerve repair procedures. In the initial part of this manuscript, experimental studies on both polysaccharides carried out by numerous authors have been presented and their results have been discussed. Further, basic information on Reaxon® Nerve Guide, being the first chitosan tube approved for clinical use, is provided. Finally, existing limitations in the optimal use of chitosan tubes in peripheral nerve reconstruction have been pointed out. It is expected that modification of the properties of chitosan itself as well as enriching neurotubes with components of extracellular matrix, cells, growth factors and filaments will further improve the results of nerve regeneration obtained with chitosan-based nerve conduits.

The anterior cruciate ligament (ACL) is cited as the most frequently injured ligament in the knee. The standard treatment of ACL injury remains ligament reconstruction followed by a postoperative physiotherapeutic procedure. During the reconstruction, the torn ligament can be replaced with an autograft or an allograft. A synthetic ligament is also one of the available graft options. Synthetic grafts in ruptured ACL treatment have been used as scaffolds, stents, or prostheses. The story of using synthetic materials in ACL deficient knee treatment started in the beginning of the 20th century with the usage of silk and silver fibers. The second half of the 20th century abounded in new synthetic materials being proposed as torn ACL replacements, such as Supramid®, Teflon® or Dacron®, Proplast®, carbon fiber graft, ABC graft, Kennedy-LAD®, Trevia, Leeds-Keio, Gore-Tex®, PDS®, EULIT®, and Polyflex® or LARS®. Artificial ligaments have intrigued surgeons for all these years as they represent the hope for grafts that are easily available and stronger than soft tissue "off-the-shelf" grafts, simplifying the surgery, and avoiding graft harvesting and donor site morbidity. However, most of the artificial grafts have been characterized by high rates of failure. One of the very few synthetic grafts gaining more widespread popularity has been LARS®. However, it is suggested that the ligament not be considered as a potential graft for primary reconstruction of the ACL, and it should be rather treated as an alternative graft in special cases, so the optimal synthetic graft material remains controversial.

Background: The development of technologies and scientific disciplines connected with medical implantation devices is dynamically affecting modern treatments by contemporary medicine and veterinary medicine; it also entails a need to monitor their impact on living organisms.

Objectives: The aim of the study was to conduct a comparative histological evaluation of the response of soft tissues after implanting monofilament fibers from resorbable glyconate and from non-resorbable polypropylene (PP) and polyamide (PA) in rats.

Material and methods: Non-resorbable polyamide-based fibers were applied to skin anastomoses in rats. Macroscopic and histological evaluations were performed on the 7th, 14th and 30th days. Non-resorbable polypropylene fibers and resorbable glyconate fibers (composed of 72% glycolide, 14% trimethylene carbonate and 4% caprolactone) were implanted in muscle tissue for periods of 7, 14, 30 and 90 days.

Results: A semi-quantitative and qualitative histological evaluation found different dynamics and degrees of intensification of cell and tissue response around the resorbable and non-resorbable fibers being tested. The resorption process of the glyconate threads caused a prolonged inflammatory cellular response compared to the non-resorbable threads; it passed, however, without the participation of giant cells. Around the non-resorbable threads the observed cellular response was less intensified, with the formation of single polymorphonuclear macrophages around the PP threads, along with a stronger degree of fibrosis and the presence of fatty infiltrate.

Conclusions: During the early period, moderately intensified inflammatory cell response with the presence of single giant cells was observed around the non-degradable PA and PP fibers. In the late period, a band of fibrous connective tissue was present around the PP threads. Glyconate fibers underwent fragmentation and the process of resorption, which was associated with a weakly intensified inflammatory process lasting up to 90 days after implantation.

Background: One of the goals of the synthetic materials used in knee joint reconstruction of the anterior cruciate ligament (ACL) is to improve the strength and stability of the graft immediately after the reconstruction. One of the synthetic grafts is a non-absorbable synthetic ligament device made of terephthalic polyethylene polyester fibers, the Ligament Advanced Reinforcement System (LARS).

Objectives: The aim of the study was to assess postoperative knee joint stability in patients who had undergone ACL reconstruction using the LARS graft.

Material and methods: The study group was comprised of 20 males who had undergone primary unilateral intraarticular ACL reconstruction using LARS. The patients were evaluated one day before the reconstruction and an average of six weeks postoperatively. Knee stability was evaluated manually using the Lachman test, anterior drawer test and pivot-shift test. Knee active range of motion (ROM) was measured.

Results: Preoperatively, the Lachman test indicated abnormal/2+ results in the vast majority of the patients. The postoperative results in most of the patients were normal/0. The anterior drawer test results were also abnormal/2+ preoperatively and normal/0 postoperatively. The pivot-shift test was positive in all of the patients before the ACL reconstruction and negative after the surgery. In general, no differences were found in the ROM between the involved and uninvolved limbs and in the between-measurement comparison.

Conclusions: The evaluation demonstrated significant progress from the preoperative to postoperative results in reducing anterior translation and anterolateral rotational instability of the tibia in patients who had undergone ACL reconstruction using the synthetic LARS graft. In the short-term follow-up assessments, restoration of anterior and anterolateral rotational stability of the operated knee joints was observed.

Background: Various surgical techniques for treating distal biceps brachii tendon injury have been described, and to date there is no consensus regarding the preferred fixation method for the anatomic reinsertion of the ruptured tendon.

Objectives: The aim of the study was to clinically and functionally evaluate the upper limb after surgical anatomic reinsertion of the distal biceps brachii tendon using an ACL TightRope® RT with a titanium cortical button and ultra high molecular weight polyethylene (UHMWPE) suture, and to assess postoperative complications.

Material and methods: The sample comprised 3 patients. Clinical examination (history, measurements of the active range of forearm motion, arm circumference, the maximum isometric forearm supination and flexion muscle torque), pain evaluation (on a visual analogue scale [VAS]) and functional assessment (the Mayo Elbow Performance Index [MEPI] and Quick Disabilities of the Arm, Shoulder and Hand [DASH]) were carried out. Complications were documented.

Results: The results of the range of motion measurements, arm circumferences and normalized isometric torque values of the muscle groups being studied were comparable in the involved and uninvolved limbs. The MEPI (x = 95.00 ± 10.42) and Quick DASH (x = 8.66 ± 18.04) scores revealed very good results. The VAS results were close to no pain (x = 3.33 ± 5.77 mm). No complications were noted.

Conclusions: The preliminary comprehensive clinical and functional assessment of the upper limb justify the clinical use of the ACL TightRope® RT with a titanium cortical button and UHMWPE suture in surgical anatomic reinsertion of the distal biceps brachii tendon. The early results with a small sample were encouraging, but studies with a larger number of cases and longer follow-up are needed.

Background: Dental composite resins - reinforced polymers - are types of synthetic resins that are used in dentistry as restorative material or adhesives. The effect of curing-light intensity on free volume sizes of 4 commercial dental composites has been studied by means of the well-known positron annihilation lifetime spectroscopy technique.

Objectives: The aim of the study was to compare the photosensitivity of 4 commercial dimethacrylate-based dental composites.

Material and methods: Positron lifetime spectra were collected using a slow-fast coincidence lifetime spectrometer with a time resolution of 365 ps. The positron source was a ~20 μCi 22Na beta emitter between two 7 μm thick stainless steel foils. The positron source was sandwiched between two identical samples under investigation. The 1st group of samples was polymerized by a 20-second photo-exposure, and the 2nd group of samples was irradiated by the blue curing light for 40 s. The positron annihilation lifetime spectrums were separated into components using the PAScual Positron Annihilation Spectroscopy data analysis program.

Results: The results showed that the lifetime component associated with free volumes differed in the different composites and depended on the irradiation time. The results indicated that the Coltene composite has higher photosensitivity than the other samples; the Denfil composite exhibited the lowest photosensitivity of the 4.

Conclusions: The appropriate light-curing intensity depends on the thickness of the composite, which in turn is proportional to the depth of the hole in the tooth undergoing repair.