Abstract:
:One approach to the controlled release of drugs involves incorporation of the drug molecules into the matrix of microscopic polymer spheres or capsules. Existing methods for preparing such microparticles do not, however, always guarantee a constant release rate, for example because drug molecules may be trapped preferentially at the surface, because they have to diffuse through an increasing thickness of polymer when the particles are non-eroding or because the surface area changes for eroding particles. In other situations pulsed release may be required--an application to which simple polymer microspheres do not readily lend themselves. Multi-walled microspheres might solve some of these problems. Here we describe a one-step process for preparing double-walled polymer microspheres with diameters ranging from about 20 to 1,000 micrometers. Our technique involves the phase separation of a polymer mixture owing to solvent evaporation: with an appropriate choice of interfacial tensions and evaporation rate, a spherical droplet of one polymer becomes coated with a highly uniform layer of the other. This process, which might be adapted to yield multi-walled microspheres, should make possible the engineering of highly specific drug-release properties.
journal_name
Naturejournal_title
Natureauthors
Pekarek KJ,Jacob JS,Mathiowitz Edoi
10.1038/367258a0subject
Has Abstractpub_date
1994-01-20 00:00:00pages
258-60issue
6460eissn
0028-0836issn
1476-4687journal_volume
367pub_type
杂志文章相关文献
NATURE文献大全abstract::The Wnt family of secreted glycoproteins mediate cell cell interactions during cell growth and differentiation in both embryos and adults. Canonical Wnt signalling by way of the beta-catenin pathway is transduced by two receptor families. Frizzled proteins and lipoprotein-receptor-related proteins 5 and 6 (LRP5/6) bin...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature756
更新日期:2002-06-06 00:00:00
abstract::Mutations in BRCA1 and BRCA2 predispose individuals to certain cancers1-3, and disease-specific screening and preventative strategies have reduced cancer mortality in affected patients4,5. These classical tumour-suppressor genes have tumorigenic effects associated with somatic biallelic inactivation, although haploins...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/s41586-019-1382-1
更新日期:2019-07-01 00:00:00
abstract::Temperature and fluid pressure conditions control rock deformation and mineralization on geological faults, and hence the distribution of earthquakes. Typical intraplate continental crust has hydrostatic fluid pressure and a near-surface thermal gradient of 31 ± 15 degrees Celsius per kilometre. At temperatures above ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature22355
更新日期:2017-06-01 00:00:00
abstract::The ability to trap an object-whether a single atom or a macroscopic entity-affects fields as diverse as quantum optics, soft condensed-matter physics, biophysics and clinical medicine. Many sophisticated methodologies have been developed to counter the randomizing effect of Brownian motion in solution, but stable tra...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature09404
更新日期:2010-10-07 00:00:00
abstract::One reason for the failure of chemotherapy in the treatment of advanced cancers may be the outgrowth of multidrug-resistant tumour cells. Multidrug resistance has been modelled in numerous mammalian cell lines in which the phenotype is characterized by a pleiotropic cross-resistance to unrelated drugs. In the study re...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/316820a0
更新日期:1985-08-29 00:00:00
abstract::A significant portion of prebiotic organic matter on the early Earth may have been introduced by carbonaceous asteroids and comets. The distribution and stable-isotope composition of individual organic compounds in carbonaceous meteorites, which are thought to be derived from asteroidal parent bodies, may therefore pr...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/348047a0
更新日期:1990-11-01 00:00:00
abstract::Tissue-specific transcription factors regulate several important aspects of embryonic development. They must function in the context of DNA assembled into the higher-order structure of chromatin. Enzymatic complexes such as the Swi/Snf-like BAF complexes remodel chromatin to allow the transcriptional machinery access ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature03071
更新日期:2004-11-04 00:00:00
abstract::Type III collagen is often found in the same tissues as type I collagen, yet the function and nature of the fibrils formed by the two collagens differ markedly. To understand the evolutionary history of the collagen gene family in more detail, we isolated the gene for type III collagen and compared its structure with ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/310333a0
更新日期:1984-07-26 00:00:00
abstract::Learning through trial-and-error interactions allows animals to adapt innate behavioural ‘rules of thumb’ to the local environment, improving their prospects for survival and reproduction. Naive Drosophila melanogaster males, for example, court both virgin and mated females, but learn through experience to selectively...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature11345
更新日期:2012-09-06 00:00:00
abstract::The bacterial CRISPR/Cas9 system allows sequence-specific gene editing in many organisms and holds promise as a tool to generate models of human diseases, for example, in human pluripotent stem cells. CRISPR/Cas9 introduces targeted double-stranded breaks (DSBs) with high efficiency, which are typically repaired by no...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature17664
更新日期:2016-05-05 00:00:00
abstract::Somatic cell nuclear transfer (SCNT) into enucleated oocytes has emerged as a technique that can be used to derive mouse embryonic stem cell lines with defined genotypes. In this issue Byrne et al. report the derivation of two SCNT Rhesus macaca male stem cell lines designated CRES-1 and CRES-2. Molecular studies deta...
journal_title:Nature
pub_type: 评论,杂志文章
doi:10.1038/nature06456
更新日期:2007-11-22 00:00:00
abstract::The Fanconi anaemia (FA) pathway repairs DNA damage caused by endogenous and chemotherapy-induced DNA crosslinks, and responds to replication stress1,2. Genetic inactivation of this pathway by mutation of genes encoding FA complementation group (FANC) proteins impairs development, prevents blood production and promote...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/s41586-019-1703-4
更新日期:2019-11-01 00:00:00
abstract::The mineral olivine dominates the composition of the Earth's upper mantle and hence controls its mechanical behaviour and seismic anisotropy. Experiments at high temperature and moderate pressure, and extensive data on naturally deformed mantle rocks, have led to the conclusion that olivine at upper-mantle conditions ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature03266
更新日期:2005-02-17 00:00:00
abstract::The long-term exchange of volatile species (such as water, carbon, nitrogen and the noble gases) between deep Earth and surface reservoirs controls the habitability of the Earth's surface. The present-day volatile budget of the mantle reflects the integrated history of outgassing and retention of primordial volatiles ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/s41586-018-0388-4
更新日期:2018-08-01 00:00:00
abstract::An amendment to this paper has been published and can be accessed via a link at the top of the paper. ...
journal_title:Nature
pub_type: 已发布勘误
doi:10.1038/s41586-020-2789-4
更新日期:2020-10-01 00:00:00
abstract::Patterns in natural systems abound, from the stripes on a zebra to ripples in a riverbed. In many of these systems, the appearance of an ordered state is not unexpected as the outcome of an underlying ordered process. Thus crystal growth, honeycomb manufacture and floret evolution generate regular and predictable patt...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/35065689
更新日期:2001-03-08 00:00:00
abstract::Cosmid, yeast artificial chromosome (YAC), P1 and complementary DNA (cDNA) libraries are distributed on high-density filters to the scientific community and experimental results are stored in a common object-based database accessible through the Internet. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/367489a0
更新日期:1994-02-03 00:00:00
abstract::Neurons in the visual cortex respond preferentially to edge-like stimuli of a particular orientation. It is a long-standing hypothesis that orientation selectivity arises during development through the activity-dependent refinement of cortical circuitry. Unambiguous evidence for such a process has, however, remained e...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/25736
更新日期:1998-09-03 00:00:00
abstract::Many animals rely on an internal heading representation when navigating in varied environments1-10. How this representation is linked to the sensory cues that define different surroundings is unclear. In the fly brain, heading is represented by 'compass' neurons that innervate a ring-shaped structure known as the elli...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/s41586-019-1767-1
更新日期:2019-12-01 00:00:00
abstract::The classical view of fast chemical synaptic transmission is that released neurotransmitter acts locally on postsynaptic receptors and is cleared from the synaptic cleft within a few milliseconds by diffusion and by specific reuptake mechanisms. This rapid clearance restricts the spread of neurotransmitter and, combin...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/385630a0
更新日期:1997-02-13 00:00:00
abstract::Mutational activation of BRAF is the most prevalent genetic alteration in human melanoma, with ≥50% of tumours expressing the BRAF(V600E) oncoprotein. Moreover, the marked tumour regression and improved survival of late-stage BRAF-mutated melanoma patients in response to treatment with vemurafenib demonstrates the ess...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature11814
更新日期:2013-02-14 00:00:00
abstract::Segmentation of the vertebrate hindbrain into rhombomeres is important for the anterior-posterior arrangement of cranial motor nuclei and efferent nerves. Underlying this reiterated organization, Hox genes display segmentally restricted domains of expression, such as expression of Hoxb-1 (refs 5, 6) in rhombomere 4 (r...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/384630a0
更新日期:1996-12-19 00:00:00
abstract::Somatic sexual differentiation in Drosophila melanogaster is accomplished by a hierarchy of genes of which one, Sex-lethal (Sxl), is required for the functional female-specific splicing of the transcripts of the immediately downstream regulatory gene, transformer (tra). The first exon of the tra primary transcript is ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/344461a0
更新日期:1990-03-29 00:00:00
abstract::The recent discovery of CD4(+) T cells characterized by secretion of interleukin (IL)-17 (T(H)17 cells) and the naturally occurring regulatory FOXP3(+) CD4 T cell (nT(reg)) has had a major impact on our understanding of immune processes not readily explained by the T(H)1/T(H)2 paradigm. T(H)17 and nT(reg) cells have b...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature07021
更新日期:2008-07-17 00:00:00
abstract::Atlantic tropical cyclone activity, as measured by annual storm counts, reached anomalous levels over the past decade. The short nature of the historical record and potential issues with its reliability in earlier decades, however, has prompted an ongoing debate regarding the reality and significance of the recent ris...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature08219
更新日期:2009-08-13 00:00:00
abstract::A variety of observations indicate that mid-ocean ridges produce less crust at spreading rates below 20 mm yr(-1) (refs 1-3), reflecting changes in fundamental ridge processes with decreasing spreading rate. The nature of these changes, however, remains uncertain, with end-member explanations being decreasing shallow ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature03140
更新日期:2004-12-09 00:00:00
abstract::All living organisms use ion channels to regulate the transport of ions across cellular membranes. Certain ion channels are classed as voltage-dependent because they have a voltage-sensing structure that induces their pores to open in response to changes in the cell membrane voltage. Until recently, the voltage-depend...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature01473
更新日期:2003-03-13 00:00:00
abstract::Understanding exotic forms of magnetism in quantum mechanical systems is a central goal of modern condensed matter physics, with implications for systems ranging from high-temperature superconductors to spintronic devices. Simulating magnetic materials in the vicinity of a quantum phase transition is computationally i...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature09994
更新日期:2011-04-21 00:00:00
abstract::Escherichia coli RNA polymerase (RNAP) synthesizes RNA with remarkable fidelity in vivo. Its low error rate may be achieved by means of a 'proofreading' mechanism comprised of two sequential events. The first event (backtracking) involves a transcriptionally upstream motion of RNAP through several base pairs, which ca...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature02191
更新日期:2003-12-11 00:00:00
abstract::Major depressive disorder (MDD), one of the most frequently encountered forms of mental illness and a leading cause of disability worldwide, poses a major challenge to genetic analysis. To date, no robustly replicated genetic loci have been identified, despite analysis of more than 9,000 cases. Here, using low-coverag...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/nature14659
更新日期:2015-07-30 00:00:00